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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        ,I@L'.@I,. @-.11 Ll
 @'                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     "@. ":@."'@'.. '@'@- - ,.--,,-" @ . .N@@I.@ @.' @ I..';,' 1. @.II@I @' I . .., ,@ , .,I@.@ %.
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        -, ,, -11.@-1.












                                               Science,
                                               Engineenng,
                                               and Public Policy
               P90perty of CSC Library


                                               Edikd by Jwnes W. Good
                                               and Sandra S. ROington
                                               COASTAL
                                               NATURAL
                                               HAZARDS










                                               oregon sea Grmt
            US Department of Commerce          0FXM-B-92M1
            NOAA Coastal services Center Library
            2234 South Hobson Avenue
            Charleston, SC 29405-2413























































                        Oregon Sea Grant, Oregon State University, Administrative
                        Services A402, Corvallis, Oregon 97331-2134

                        @ 1992 by Oregon State University. All rights reserved.


                        ISBN 1-881826-00-7






            CONTENTS




                Support v


                Preface vi


            SCIENCE

            PACIFIC NORTHWEST COASTAL EARTHQUAKE, TSUNAMI, AND LANDSLIDE HAZARDS
                Seismic Hazards on the Oregon Coast 3
                    Ian Madin

                Seismic Hazards on the Oregon Coast-A Response 28
                    Richard W. Rinne

                Comments on Paper by Ian Madin 32
                    Rainmar Bard

                Catastrophic Coastal Hazards in the Cascadia Margin U.S.
                Pacific Northwest 33
                    Curt Peterson and George Priest

            COASTAL PROCESSES AND HAzARDs

                Ocean Processes and Hazards along the Oregon Coast 38
                    Paul D. Komar

                Comments on Paul Komar's "Coastal Zone Processes
                and Hazards" 74
                    John Beaulieu


            ENGINEERING

            SHORE PROTECTION AND ENGINEERING
                Shore Protection and Engineering with Special Reference to
                the Oregon Coast 79
                    Nicholas C. Kraus and William G. McDougal
                A Discussion of "Shore Protection and Engineering with Special
                Reference to the Oregon Coast" 101
                    Spencer M. Rogers, Jr.

                Responding to Oregon's Shoreline Erosion Hazards: Some Lessons
                Learned from California 104
                    Gary B. Griggs

                Shore Protection and Engineering: A Local Perspective 117
                    Matt Spangler















                       PUBLIC POLICY

                       COASTAL HAZARDS POLICY ISSUES ON THE WEST COAST
                           Recent Legal Developments in Coastal Natural Hazards Policy 121
                               Richard G. Hildreth

                           California's Coastal Hazards Policies: A Critique 127
                               Gary B. Griggs, James E. Pepper, and Martha E. Jordan
                           Washington State Coastal Hazard Initiatives 139
                               Douglas J. Canning

                           Ocean Shore Protection Policy and Practices in Oregon 145
                               James W. Good




















































                        iv






            SUPPORT






                                        This book is funded by the National Oceanic and
                                        Atmospheric Administration, through Oregon Sea
                                        Grant (grant number NA89AA-D-SG108). The
                                        views expressed herein are those of the authors
                                        and do not necessarily reflect the views of NOAA
                                        or any of its subagencies.













































                                                                                                         v






                             PREFACE






                             in early October 199 1, more than 160 coastal ge-       Coast and learned about the successes and short-
                             ologists, oceanographers, engineers, planners, re-      comings of public policies designed to deal with
                             source managers, and citizens gathered in New-          development in hazardous areas.
                             port, Oregon, to learn about recent research on           This book is a collection of the principal pa-
                             coastal natural hazards and discuss the implica-        pers delivered at that conference, along with cri-
                             tions for coastal development and management.           tiques and supplementary remarks of panelists.
                             At that conference, "Coastal Natural Hazards:           For the most part, the papers are written in
                             Science, Engineering, and Public Policy," distin-       nontechnical language, with ample illustrations.
                             guished scientists, engineers, and policy analysts      As such, they serve as useful primers for the new-
                             reviewed the state of knowledge in their special-       comer to the subject, whether a local official,
                             ties. We learned about the effects of periodic El       property owner, realtor, or coastal visitor. To-
                             Niflos on beach and shore erosion and about re-         gether, the papers should also be a useful refer-
                             cent research on factors that control sea cliff erO-    ence for the policymaker, emergency manager,
                             sion. Scientists presented evidence for periodic        professional planner, beach and coastal manager,
                             great subduction zone earthquakes that have oc-         academic, and student. And for Iong-time observ-
                             cuffed along the Pacific Northwest coast and            ers of the coastal scene, the papers will confirm
                             speculated on when the next quake might strike.         many of their hunches about die workings of our
                             We were introduced to planning and engineering          dynamic Pacific Northwest coastline.
                             approaches to hazard mitigation on the West





























                             vi








                                                                                                                                                                                                        COMM)


                                                                                                                                                                                                        CIMM)


                                                                                                                                                   . . . . . .     ..... .... .



                                                                                    . . . . . . . . . .

                                                                                                                                                                                                                  iA
                                                                                                                                                                                                                                                                                                                                                           . ........ . . .
                                                                                                                                                                                                                                                                                                     ...........





                 SEISMIC HAZARDS ON THE OREGON COAST                                                                                                             SCIENCE

                 Ian Madin
                 Oregon Department of Geology and Mineral Industries


                 Seismic hazards have been considered a relatively                    Plate Tectonics: The Driving Force
                 minor threat in Oregon for most of our recorded                                                                                           PACIFIC
                                                                                         ne theory of plate tectonics explains the                         NORTHWEST
                 history. Recent advances in the geological and                       large-scale structure of the surface of the earth                    COASTAL
                 seismological understanding of earthquakes in                                                                                             EARTHQUAKE,
                 Oregon changed this perception during the 1980s,                     and major earth movements. The theory is based                       TSUNAMI, AND
                                                                                      on the assumption that the rigid outer rock shell                    LANDSLIDE
                 and there is now fairly widespread acceptance                        of the earth, called the crust, is essentially floating              HAZARDS
                 among the scientific community that Oregon, par-                     on a plastic or semiliquid layer 100-150 kilome-
                 ticularly coastal Oregon, faces significant seismic                  ters deep in the earth's mantle (figure 1). Over
                 hazards. In this paper I explain the changes in sci-                 hundreds of millions of years, circulation in the
                 entific understanding that led to this conclusion                    body of the earth has broken the crust into frag-
                 and describe the many types of hazards associ-                       ments the size of continents. These fragments are
                 ated with earthquakes. In addition, I illustrate ex-                 called plates, and as they move slowly across the
                 amples of the evaluation of hazard-prone areas,                      face of the earth, they interact with each other
                 using the coastal geologic hazard maps published                     along their edges, producing earthquake and vol-
                 by the Oregon Department of Geology and Min-                         cariJc activity. The boundaries between plates
                 eral Industries (DOGAMI).                                            take one of three forms: divergent boundaries,
                     This paper is intended for a lay audience,                       where plates pull apart; convergent boundaries,
                 Thus, in the interest of clarity, I have omitted                     where plates come together, and transform
                 many arguments and details of the scientific data.                   boundaries, where plates slide horizontally past
                 Although I cite many sources, the paper is not a
                 complete review of the existing literature.                          one another.



                                                                                          (a) Spreading boundary          (b) Convergent boundary


                                                                                                                                                          Figure 1. Three types
                                                                                                                                       Al                 ofplate boundaries. A
                                                                                                                                                          spreading boundary
                                                                                                                                                          (a) ntarks the
                                       .",,Fracture zone                 (c) Transfor boundary                                                            divergence of1wo
                                                                                                                                                          plates. A convergent
                                                                                                                                                          boundary (b) occurs
                                                                                                                                                          where one p late moves
                                                                                                                                                          toward another. A
                                                                                                                                                          transform boundary
                                                                                                                                                          (c) occurs where
                                                                                                                                                          relative plate motion
                                                                                                                                                          is parallel to the plate
                                                   Upwelling                                                              Subducting                      edges. After Noson
                                                 mantle rocks                                                                Juan cle Fuca plate          and others, 1988.











                                                                                                                                                   3







                                                                                          Around the world, the majority of earthquake
                                                                                       and volcanic activity is concentrated along the
                                                                                       plate boundaries. Spreading centers produce
                                                                                       huge, but relatively quiet, eruptions of basalt.
                           .. ..... . ... .
                                                                                       Subduction zone volcanic chains create smaller,
                                                                                       but often explosive, eruptions of lava and ash.
                                                                            0//X
                                                                                       Spreading centers produce normal fault earth-
                                                 '0
                                                                                       quakes, caused by the pulling apart of the crust,
                                                    0//X                               which are typically no larger than magnitude 6 or
                                                                                       7. Transform b9undaiies create earthquakes up to
       Figure 2. Plate
                                                                                       magnitude 8 along horizontal slip faults, where
       tectonic selling
       of the Pacific                                                                  the opposite sides of the fault move horizontally
                         . ....... .   ...
       Northwest.
                                                                                       past each other. Subduction zones produce thmst
                              ....... ..... ............
                                 ..........-
                                 ......... . .-
                                 ............ . .
                              ........ .   .......                                     earthquakes, where one side of the fault is shoved
                            J 'a:n:::A.,e.::,:
                              Ju.             F
                                                                                       beneath the other. These subduction. earthquakes

                                      .. ....... .. ..
                                                                                       are the largest recorded, with magnitudes com-
                                            PI*                                        monly greater than 8. Subduction zones also pro-
                                                ate-
                                                                                       duce intraplate earthquakes up to magnitude 7 or

                                                 ...........
                                                                                       8 in the subducting plate, as it buckles on its way
                                                                                       down into the body of the earth.
                                                 ..........



                                              . . .. .. ........
                                                                                       Cascadia: The Faults under Our Feet
                                              . ........... .
                                                    ...........
                                              . ........... ........
                                                                                          The Pacific Northwest is endowed with ex-
                                                                                       amp es of all three types of plate boundaries, as
                                                                                       three. plates interact in the region. Oregon is situ-
                                                                                       ated on the North American Plate (figure 2),
                                 At divergent boundaries, spreading centers            which stretches from the Pacific coast of the U.S.
                              form where lava erupts along the length of the           to the middle of the Atlantic Ocean. To the west
                              boundary, congealing to form new crust. As the           of the North American Plate is the Pacific Plate,
                              plates continue to pull apart, the newly formed          the largest on the planet, which extends to
                              crust splits, half with each plate, and this process     Alaska, Japan, and Antarctica. Last and least,
                              creates tens to hundreds of kilometers of new            sandwiched between these two giant plates is the
                              crust over millions of years. The crust formed by        Juan de Fuca Plate, which forms the deep ocean
                              this process is composed of dense basalt rock,           floorjust off the coast of Oregon and Washing-
                              which floats low in the mantle and therefore             ton. The Pacific and North American plates share
                              makes up the floors of the earth's oceans.               a transform boundary in California (San Andreas
                                 Where two plates collide in a convergent              Fault) and northern British Columbia (Queen
                              boundary, one will typically duck beneath the            Charlotte Fault), and the Pacific Plate moves in-
                              edge of the other and be pushed or pulled several        exorably north past North America along these
                              hundred kilometers into the depths of the earth.         two great horizontal slip faults. Dozens of major
                              This process is called subduction. When the sub-         historical earthquakes on these transform faults
                              ducted plate is sufficiently deep, it melts; the re-     clearly indicate that these are active plate bound-
                              sultant magma rises to feed a chain of volcanoes         aries. The Juan de Fuca and Pacific plates are
                              parallel to the convergent boundary. This kind of        separated by a spreading center, which is very
                              plate boundary, called a subduction zone, con-           seismically active and which has experienced
                              sumes the crust produced at spreading centers.           undersea volcanic eruptions in the last few years.
                                 At a transform boundary, two plates simply            Finally, there is a subduction zone plate bound-
                              slide past each other horizontally, and crust is         ary between the Juan de Fuca and North Ameri-
                              neither produced nor consumed.                           can Plates. The Juan de Fuca Plate slides beneath

                              4







                the North American Plate along a great fault that         occurs in geographically discrete source zones.
                extends from Cape Mendocino in Califomia to               Although the three types have distinct character-
                Vancouver Island in British Columbia. This great          istics, they are all driven by the convergence of
                fault is called the Cascadia subduction zone              the North American and Juan de Fuca plates
                (CSZ). The CSZ originates (figure 3) at the base          across the CSZ. Crustal earthquakes occur within
                of the continental slope off Oregon and Washing-          the North American Plate at depths of 10 to 20
                ton, and angles gently beneath the North Ameri-           kilometers. Intraplate earthquakes occur within
                can Plate. It reaches a depth of 100 to 150               the descending Juan de Fuca Plate at depths of 40




                                                                                  NORTH
                                                                                   M E@R
                                                                                         PLAT

                                                               ......:                   SEA
                                            UAN D                                                               Figure 3.
                                                                                                                Schentalic cross
                                                                                                                section of the
                                     PACIFIC             FU                 _0                                  Cascadia
                                                                         .......... I-
                                                                                        POX
                                                                               vA                               subduction zone
                                       PLATE                                    -
                                                                                0-                              (CSZ).



                                                                                UM' NON
                                                       PLATE








                kilometers beneath the high Cascades, where the           to 60 kilometers. Subduction earthquakes are hy-
                Juan de Fuca Plate melts to feed the Cascade vol-         pothetical, as none have been observed, but they
                canoes. As such, this great fault underlies virtu-        are believed to occur in the upper portion of the
                ally all of Oregon, and along the coast it may be         CSZ, along the great fault which separates the
                as little as 30 or 40 kilometers down. Because all        two plates.
                of the other plate boundaries in the area and the         Crustal Earthquakes: Close to Home
                Cascade volcanoes are active, we conclude that
                the CSZ is also active. The Juan de Fuca Plate is            In Oregon, the majority of historical earth-
                probably subducting along the CSZ at 3.8 to 4.8           quakes have probably been crustal events. Most
                centimeters per year (Riddihough 1984), a rate            of these earthquakes have occurred in the Port-
                quite similar to the 3.3 to 4.8 centimeters per year      land area, the Willamette Valley, the northem Or-
                measured and estimated on the San Andreas Fault           egon Cascades, and eastem Oregon. Coastal
                (Harbert 1991). The clear conclusion is that Or-          Oregon has been almost completely devoid of
                egon sits on top of the CSZ, a major active plate         earthquakes, with the exception of a cluster of
                boundary fault.                                           small events near Newport, and the 1863 Port
                                                                          Orford earthquake (Jacobson 1986; Johnson and
                Earthquake Sources: The Triple Threat                     Scofield 199 1), both of which occurred before the
                   From our understanding of the plate tectonic           establishment in 1970 of modem seismic net-
                setting of the Pacific Northwest, we can identify         works in the Pacific Northwest. As a result, it is
                three possible earthquake types (figure 4): crustal,      not known whether these earthquakes are crustal
                intraplate, and subduction. Each of the thme types        or intraplate. The history of seismicity along the


                                                                                                                                 5









                                                                                                         nL@nploLe Ecr-thquoke up Lo M 7.4
                                                             C                                                  I--- Y.
                                                              S                                            JDF        @S@Z
                                                               Z

                              Figure 4.                                                                 CrusLol Eew-LFcpoke up Lo M 6.5
                              Earthquake source         JDF
                              zones in the Pacific
                              Northwest. CSZ =                                                                                    @ NAM
                              Cascadia subduction                                                                                ou
                              zone; JDF = Juan de
                              Fuca Plate; NAM
                              North American
                              Plate; PAC = Pacific   1%,                                NAM
                              Plate.                                                                    SubducLian Ecr-UqL@e M 8-9?
                                                      PA

                                                                                                                                     NAM




                              Oregon coast may suggest that there is little threat      Brookings. If that earthquake had been 50 kilo-
                              from crustal earthquakes. However, the record of          meters closer, damage could have been wide-
                              historical seismicity extends only to 1841, and           spread. Where potentially active crustal faults
                              instrumental measurement of earthquakes in Or-            occur beneath urban areas, the possibility exists
                              egon began only in the late 1950s.                        for damaging earthquakes.
                                The geologic record suggests that crustal earth-           From what is now known, most of the Oregon
                              quakes may pose some hazard at a few sites along          coast is probably not greatly at risk from crustal
                              the coast. McInelly and Kelsey (1990) reported            earthquakes. Detailed fault mapping of the coast
                              numerous faults in the South Slough-Charleston            has been in progress for only a few years, and
                              region of Coos Bay that may represent a seismic           seismic monitoring capabilities on the coast have
                              hazard (figure 5). The various faults have broken
                              and offset marine terrace deposits that are prob-
                                                                                                                    Z
                              ably only 80,000 to 120,000 years old and hence
                              may have some potential for future movement.
                              The mapped extent of these faults is short, which
                                                                                                                           @4A
                                                                                                                           7-
                                                                                                    4'i
                              may suggest that they are not capable of generat-
                                                                                                                           Norlk
                              ing earthquakes greater than magnitude 5 to 6.
                                                                                                                           Bend
                              Work in progress (Harvey Kelsey, personal com-             '1!@ _iM, T! -:19- A
                                                                                                                                   A
                              munication, 199 1) suggests faults near Alsea Bay
                                                                                                                              Coos
                              which offset marine terrace deposits, also a few
                                                                                                                              Boy
                              hundred thousand years old. Finally, detailed off-
                                                                                                                 lesLon
                              shore geologic mapping (Goldfinger and others
                              1990) has identified dozens of major offshore
                              crustal faults that appear to have moved in at least
                                                                                                                                      :V?
                              the last 1.6 million years (Pleistocene time), pos-
                              sibly as recently as the last 10,000 years (Holo-
                              cene time). These faults pose a potential threat,          H-
                              particularly if they extend onshore. Similar off-
                                                                                                                              CS'




































                              shore crustal faults have been responsible for sig-
                              nificant historical earthquakes, including the
                              magnitude 6.6 earthquake of July 12, 1991,                Figure 5. Schematic map of known Quaternaryfaults in
                              which occurred 110 kilometers west of                     the Coos Bay area. After McInelly and Kelsey, 1990.

                              6







                always lagged behind the rest of the
                state. Improved seismic moii@itoring by
                the Urdversity of Oregon and University
                of Washington should help to define                                                            NAM
                potential crustal faults along the coast.
                Ongoing coastal fault studies by West-                        C                              Z2@
                ern Washington State University
                (Harvey Kelsey), University of Oregon                           S                         /P\
                (Ray Weldon), the U.S. Geological                                Z   AsLorlo
                Survey (Ray Wells, Parke Snavely) Or-                                                    PorLlcwid               Figure 6. Potential
                egon State University (Vern Kulm,                                                                                source zonefor
                Chris Goldfinger, John Dilles), and                JDF                                                           magnitude 7+
                                                                                                                                 intraplate
                DOGAMI (Ian Madin) should also pro-                                                                              earthquakes. From
                vide a more reliable estimate of crustal                                                       Z@'               Weaver and
                                                                                                                                 Shedlock, 1989.
                earthquake hazards.                                                                             /0\
                Intraplate Earthquakes: Danger in
                the Depths
                  In western Washington, the majority                                Coor.
                of damaging historical earthquakes have                              Bay     ?
                been intraplate earthquakes, which oc-          PAC
                cur in the descending Juan de Fuca Plate
                (figure 4). The largest of these earth-
                quakes was the magnitude 7.1 Olympia
                earthquake of 1949. Along the Oregon                                                          zf@
                coast, a small number of earthquakes
                have been positively identified as intraplate           capabilities being installed by the Universities of
                events. The largest of them was a magnitude 2.8         Washington and Oregon will provide a more reli-
                event that occurred at a depth of 41 kilometers         able estimate of the hazard of intraplate earth-
                near Newport in June 1981 (Weaver and Baker             quakes. It is clear that a major source of potential
                1988). This suggests that many of the other earth-      earthquakes as large as magnitude 7 underlies the
                quakes located in the Newport area before 1970          entire Oregon coast, but it is not clear whether
                may have been intraplate events. The largest            these earthquakes will happen sufficiently often
                intraplate event in Oregon may have been the            to present a significant hazard.
                1873 magnitude 6.7 Port Orford earthquake. This         Subduction Earthquakes: The Big One
                event was felt along the southern Oregon and               No large earthquakes have been reported from
                northern California coasts and had no after-            the CSZ during the 150 years of recorded history
                shocks. The absence of aftershocks has led to           in the Pacific Northwest, and modem seismic net-
                speculation that it was an intraplate earthquake:       works detect essentially no earthquakes in the
                intraplate earthquakes typically do not have after-     zone. This has led seismologists to speculate that
                shocks (Ludwin and others 1989). Weaver and             subduction on the CSZ, although almost certainly
                Shedlock (1989) have proposed that much of the          active, is aseismic and never produces large
                Oregon Coast from Astoria to Waldport and from          earthquakes (Ando and Balazs 1979). However,
                Cape Blanco to the California border is suscep-
                                                                        Heaton and Kanamori (1984) discussed the seis
                tible to intraplate earthquakes as large as magm-       mic potential of the CSZ and noted that it shared
                tude 7 (figure 6).                                      many characteristics with other subduction zones
                  No amount of surface geological investigation
                                                                    C


















                will improve our understanding of intraplate            which had great earthquakes. They concluded
                earthquakes, which occur 45 to 60 kilometers be-        that the Juan de Fuca Plate was similar to other
                                                                        subduction zones in which active subduction was
                neath the surface. Improved seismic monitoring          accompanied by a great earthquake of magnitude

                                                                                                                          7







                               8 or larger. Adams (1984) studied modem defor-
                                                                                                                .. .........
                               mation of the CSZ using leveling, tide gauge, and
                                                                                                                   . .........
                               geomorphic data and concluded that it was pos-
                                                                                                               ..... ... .....
                               sible that subduction was accomplished durin
                                                                                         9             ......
                               great subduction earthquakes every 200 to 5
                                                                                         00
                               years. Adams also noted that it might be possible
                                                                                                             ...........-. . .....

                                                                                                             .. . ........ ..........
                               to search for evidence of prehistoric great earth-
                                                                                                                        ............
                               quakes by looking for disturbed layers in lake
                               sediments, landslides triggered by earthquakes,
                                                                                                                    .............
                                                                                                                                      own
                               periodic submarine landslide deposits, and up-
                                                                                                 ..............

                                                                                                 .................-
                               lifted or subsided coastal features. Other research-
                                                                                                              ..............
                                                                                                                 ......               .....
                                                                                         the            ...............
                               ers (Byme and others 1988) contended that                         ............... . .
                                                                                                                .............
                               rocks in the CSZ are sufficiently weak and hot
                                                                                                            ................ .............. ....
                                                                                                 ...........
                                                                                               ..........
                                                                                                                .............
                               that they act in effect as a lubricant, allowing sub-
                                                                                                   ................. ... . ........ ............
                                                                                                                   ..........
                               duction to proceed without any great earthquakes.
                               The picture is ftwffier complicated by the example
                                                                                                  . ............... .................. . .
                                                                                                 PI
                                                                                                    A,
                               of the San Andreas fault, which has "aseismi-                                 ............

                                                                                                        ............
                               cally" creeping segments, which produce con-
                                                                                                        ............ ...... . .. .. M.
                               stant microearthquakes, and an almost completely                  .. . ........
                                                                                                      ......... .

                                                                                                     ............
                               aseismic segment, which moved in 1906 to
                                                                                                                                 0 w
                               produce the great San Francisco earthquake.
                                                                                                             WN
                               Without direct evidence, the earlier debate was
                                                                                                    ...........
                               largely academic, as them was no way to prove or
                               disprove the hypothesis of great earthquakes on              Figure 7. Schematic diagram of land level changes that
                                                                                            occurred during the 1960 Chilean earthquake (Mw 9.5).
                               the CSZ.                                                     After Plafker, 1972.
                               Buried Marshes: The Smoking Gun                              flex slowly, as shown in figure 8. When the earth-
                                                                                            quake occurs, the flex is released and the land
                                   The theoretical arguments about whether or               rises or subsides accordingly. The earthquake
                               not the CSZ moved in periodic great earthquakes              cycle produces a distinctive pattern of land level
                               were overshadowed by Brian Atwater's (1987)                  changes, with slow steady uplift or subsidence
                               discovery of direct geologic evidence for prehis-            between earthquakes that instantaneously re-
                               toric great earthquakes. Atwater's study was the             verses during the earthquake. This phenomenon
                               first to find direct evidence of great CSZ earth-            can be used in effect as a natural seismograph to
                               quakes and was based on looking for the geologic             record preffistoric earthquakes, because the sea
                               footprint of a great earthquake. Other great sub-            leaves a "ring around the bathtub" on the land. As
                               duction earthquakes around the world-Alaska,                 the land moves up and down with respect to sea
                               1964, and Southern Chile, 1960 (Plafker 1972)--              level, coastal processes leave geologic features
                               produced distinct and gigantic footprints on the             and deposits that form at very specific elevations.
                               land. Typically, the upper plate in the subduction           Where the land is uplifted, wave-cut platforms or
                               zone undergoes immediate and permanent land                  beach ridges formed at or below mean tide level
                               level changes during a great subduction earth-               are often stranded high above the highest tides.
                               quake with a pattern as shown in figure 7. The               Where the land subsides, freshwater marshes or
                               leading edge of the upper plate is uplifted, with            lowland forest lands may sink below the level of
                               subsidence farther inland and less pronounced                the fides and be converted to intertidal mudflats.
                               uplift farther inland yet. The simple mechanical                Atwater (1987) studied Willapa Bay in south-
                               explanation for this pattern is that during the hun-         western Washington, where he noted a distinctive
                               dreds of years between earthquakes, the two                  pattern of sediment in the banks of tidal channels
                               plates are locked together but still converging.             in modem marshes. Typically, the modem veg-
                               This steady convergence causes the upper plate to            etation would be found growing on a modem

                               8







                                                                      observed sand layers directly above several of the
                                                                      buried marsh peats, which he speculated might
                                                                      have been deposited by tsunamis (popularly
                                                                      known as tidal waves) generated by the same
                                                                      earthquake that caused the subsidence.
                                                                        Atwater's discovery provided the first geologic
                                                                      evidence that great megathrust earthquakes might
                                                                      have occurred before the arrival of Europeans in
               Interseismic                                           the Pacific Northwest, but there were still many
                                                                      skeptics, many unanswered questions. Perhaps
               Strain                                                 the burial of the marshes was due to floods, storm
               Upper plate bows up, tideflats                         surges, breaches of spits, distantly generated tsu-
               become marsh and forest.                               namis, or periodic great forest fires that choked
                                                                      streams with silt and filled in bays. Alternatively,
                                                                      it might be possible that the land had indeed sub-
                                                                      sided in an earthquake, but in a minor earthquake
                                                                      on a lo al fault instead of a great earthquake
                                                                      stretching from Vancouver Island to California.
                                                                        Subsequent to Atwater's original research in
                                                                      Willapa Bay, other researchers began to explore
                                                                      Oregon estuaries for similar evidence. They
                Coseismid                                             found it in almost every significant estuary along
                                                                      the northern and central coast (figure 10). Grant
                Strain                                                and McLaren (1987) found evidence for several
                 Bowed upper plate relaxes, marshes                   episodes of abrupt marsh subsidence and burial at
                 and forests converted to tideflat.                   the Salmon and Nehalem River estuaiies.
               Figure 8.                                              Peterson and Darienzo (in press) and Dahenzo
                                                                      and Peterson (1988, 1990) discovered multiple
                                                                      abruptly buried marshes in the estuaries of the
               peat, which would grade down into deposits of          Necanicum, Nestucca, Little Nestucca, Siletz,
               intertidal mud. This sequence suggests that the        Alsea, and Yaquina rivers, and at Netarts Bay.
               land slowly rose with respect to sea level, expos-     Nelson and Personius (in press) have found bur-
               ing tide flats above the range of tides and allow-     ied marshes in South Slough, and Peterson and
               ing freshwater plants to colonize the surface.         Darienzo (personal communication, 1991) have
               However, beneath this sequence, Atwater found a        detected preliminary evidence of buried marshes
               buried, fossilized peat layer (figure 9) separated     in the estuaries of the Siuslaw, Coquille, and
               from the overlying intertidal mud by an abrupt         Umpqua rivers, and in Catching Slough, although
               boundary. The fossilized peat in turn graded           Nelson and Personius (in press) found conflicting
               downwards into intertidal mud, underlain by yet        evidence in these estuaries. In northern Califor-
               another layer of buried peat. This sequence of al-     nia, Carver (199 1) discovered buried marsh lay-
               ternating buried peat and interfidal mud strongly      ers in Humboldt Bay.
               suggests that the land has undergone cycles of            Clearly, the phenomenon of abruptly buried
               slow uplift that allow marshes to colonize             marshes is not due solely to local faults in
               mudflats, followed by abrupt subsidence that bur-      Washington. All along the Cascadia subduction
               ies the marsh in intertidal mud. This is exactly the   zone, repeated cycles of slow uplift followed by
               sequence of deposits expected to form during           rapid submergence of the land have occurred,
               cycles of great earthquakes and is in fact quite       with many submergence events accompanied by
               similar to buried marsh and forest deposits            tsunamis. The simplest explanation for these
               formed during the 1964 Alaskan and 1960 Chil-          deposits is the periodic occurrence of great
               ean (Atwater 1989) earthquakes. Atwater also           subduction earthquakes that involve hundreds of

                                                                                                                          9










                                                                                              'q@ -    A
                                                                                                                       @ 4A
                                                                                                      -4























                                                                                                          4f*V
                                Figure 9. Buried                                                                                         A 1,
                                marsh exposed in
                                tidal channel, Willapa
                                Bay, Washington.
                                Modern marsh grades
                                down into interfidal
                                                                                     'A
                                mud, which abruptly
                                overlies buried marsh
                                                                                                     14
                                (dark band at
                                bottom). Thin grey
                                layers labelled "s"
                                are tsunami sand
                                deposits. From
                                                                                                                                              All,
                                Atwater and
                                Yamaguchi, 1991.










                                                                                                                 40

                                                                                                                                                 A



                                                                                                 Al




                                                                                  ",4

                                                                                                                                            Ir
                                                        L


                                kilometers of the coast all at once. If true, the          Corroborating Evidence: More Pieces
                                implications for Oregon coastal communities are            of the Puzzle
                                awesome, because such an earthquake would                     Although the evidence from buried marshes is
                                cause simultaneous strong shaking and coastal              fairly persuasive, it is vital to look for other evi-
                                subsidence, which would be followed quickly by             dence to prove the great earthquake hypothesis.
                                a local tsunami.




                                10







                                                                                turbidity current leaves a distinctive layer of sedi-
                                                                                ment, called a turbidite, and it is possible to count
                                                                                the number of turbidity currents that have passed
                                                             %\                 any given site by counting the turbidite layers.
                                  N.
                                                                                Griggs and Kulm (1970) first noted that sediment
                                                                                cores from a number of submarine channels off
                                                                                the coast of Oregon and Washington could be
                                                            oncj                used to count the number of turbidity currents
                                                 Por
                                                                                that had occurred since the eruption of Mt.
                                                                                Mazarna (now Crater Lake) about 7,000 years
                                                        elem
                                                                                ago. They determined this by counting the num-
                                                                                ber of turbidites above the first layer which con-
                                                                                tained the distinctive ash from Mt. Mazarna. In
                                                                                his analysis, Adams (1990) noted that there were
                                                        ugene                   similar numbers of post-Mazama turbidites in the
                                                                                upper reaches of many channels along the coast.
                                                                                Most important, he noted that even where two
                                                                                channels came together, there were the same
                                               Roseburg                         number of turbidites below the confluence as
                                                                                above. This requires the turbidity currents in each
                                                                                channel to have been triggered simultaneously.
                                                                                Adams (1990) argues that the only plausible ex-
                                               GrCnLs Poss                      planation for simultaneous triggering of turbidity
                                                                                currents at sites tens to thousands of kilometers
                  Figure 10. Sites with multiple buried marshes an the          apart is a great subduction earthquake.
                  Oregon coast.                                                    Geodetic techniques compare very precise
                                                                                measurements of the position and elevation of a
                  The adverse consequences of spending money                    network of stations over time to determine how
                  and restricting coastal development unnecessarily             the land is currently expanding or contracting,
                  in response to a false subduction earthquake                  rising or falling. The first attempt to use geodetic
                  threat are-probably outweighed only by the con-               data to constrain the behavior of the CSZ was by
                  sequences of preparing inadequately for a true                Ando and Balazs (1979), who used historical lev-
                  threat. Although earthquake-related subsidence                eling data to show that the Oregon Coast Ranges
                  remains the only satisfactory explanation for the             were tilting to the east. 'Mey concluded that the
                  buried marshes, it is important to look for other             Juan de Fuca Plate was subducting aseismically
                  types of evidence. To date this has come from                 and would not have great earthquakes. Adams
                  undersea landslides, modem geodetic measure-                  (1984) looked at historical data as well as geo-
                  ments, Indian legends, and archaeological sites.              logic data to determine long-term deformation
                     Adams (1990) has proposed a completely in-                 rates all along the CSZ. He concluded that the
                  dependent line of evidence for great subduction               modem deformation did not require aseismic sub-
                  earthquakes based on submarine landslide depos-               duction and suggested that great earthquakes
                  its. Sand, silt, and clay flushed into the coastal            might occur. Vincent (1989), and later Weldon
                  waters of Oregon and Washington by rivers accu-               (1991), used historic leveling data and tidal
                  mulate in thick deposits offshore on the continen-            records along the Oregon coast and across the
                  tal shelf and slope. Periodically these piles                 Coast Ranges to show that parts of the coast are
                  become unstable and slump in a submarine land-                clearly rising at a significant rate. This result is
                  slide, causing a slurry of sediments and water                very important because it shows clearly that the
                  (called a turbidity current) to flow down subma-              Juan de Fuca and North American plates are in
                  rine channels onto the deep abyssal plain. Each               fact locked together, and not slipping aseismically


                                                                                                                                           I I







                              past one another on some layer of sedimentary                ans at Neah Bay recorded by James Swan states
                              "grease." Both studies note that the amount of               that the waters of the bay receded dramatically
                              geodetically measured uplift is dramatically less            for four days, then returned to flood the land for
                              along the north-ceno-al Oregon coast than areas              another four days before receding. The same leg-
                              farther north or south (figure 11), which suggests           end described a permanent land level change at
                              that the subduction zone is broken into small in-            the same time, with an island being converted to a
                              dependent segments.                                          peninsula, although it also noted that the water
                                                                                           that flooded the community was hot. Woodward
                                                                                           (1990) reports a similar tsunami legend from the
                                                                                           Tillamook area. Unfortunately, Indian legends are
                                                                                           somewhat ambiguous about the timing of events,
                                                                        eatIle
                                                                                           and contain enough references to clearly super-
                                                                                           natural occurrences that they provide only weak
                                                                          North            corroborating evidence to the great earthquake
                                                                                           hypothesis.
     Figure 11. Schematic
     representation of        3@
                                                                                              More concretely, Woodward (1990) noted
                                   ju
     geodetically
                                                                                           archaeological evidence for significant changes in
     measured                             @uij;z@   ir
     deformation in the
                                                                    Portland               the lifestyles of Indians along the coast of Oregon
     Pacific Northwest.
                                                                                           which have occurred at times coincident (see
     Vertical data in         V@
     Oregonfrom                                                     American               discussion below) with hypothetical prel-dstoric
     Weldon, 1991.                                                                         subduction earthquakes. At Nehalem Bay,
     Horizontal data in                                                                    Woodward reports an Indian campsite dated to
     Washingtonfrom
     Savage and Lisowski,                                                                  380 years before the present (BP) that is now
                                                                                           permanently below tidal levels. In Tillamook
                                                                                           Bay, changes in species of shellfish deposited in
                                                                          Plate
                                                                                           middens suggest a change from a bay environ-
                                                                                           ment to open shore at 1070 years BP. At Netarts
                                                                                           Bay, shell middens at an Indian campsite formed
                                                                                           1,400 years ago have now subsided below the
                                                                                           level of high tides. 'Me results from these sites
                                                                                           and others are intriguing, but they provide only
                                 In Washington, Savage and Lisowski (1991)                 circumstantial evidence of major, perhaps cata-
                              measured the ongoing deformation of the Olym-                strophic changes in coastal Indian settlements that
                              pic Range with precision laser instruments. They             may have accompanied great earthquakes.
                              concluded that the Olympics are cun-ently being                 The evidence listed above is consistent with a
                              shortened horizontally in a direction essentially            history of great megathrust earthquakes in the Pa-
                              parallel to the direction of subduction of the Juan          cific Northwest, and a majority of geoscientists
                              de Fuca plate (figure 11), and this shortening is            working in the region now accept that these
                              consistent with the accumulation of strain energy            events have occurred. Them are, however, prob-
                              on a locked subduction zone.                                 lems with the theory of great subduction events,
                                 These preliminary results from geodetic stud-             which are reviewed in the following section.
                              ies still leave questions about the shape of the
                              locked portion of the subduction zone and about              Conflicting Evidence: It's Not a Done
                              our current position in the strain cycle, but they           Deal
                              are inconsistent with the notion of subduction
                              without great earthquakes.                                      One of the most fundamental problems with
                                 Indian legends of great earthquakes and tsuna-            the great earthquake story is the assumption that
                              mis are known from the Pacific Northwest.                    the buried marsh layers are in fact due exclu-
                              Heaton and Snavely (1985) report several legends             sively to abrupt land subsidence during earth-
                              from the region. One legend of the Makah Indi-               quakes. Alternating layers of peat and intertidal

                              12







                mud are known from coastal regions without sub-         estuaries that did not subside. This implies that
                duction zones (Nelson and Personius, in press).         tsunami sands should be distributed throughout
                Atwater (1987) and Atwater and Yamaguchi                the peat and intertidal mud layers if there am nu-
                (199 1) cite a variety of evidence from Washing-        merous independent events. On the Oregon coast,
                ton marshes that seem to require earthquakes to         Darienzo and Peterson (1988, 1990), Peterson
                explain buried marshes. Peterson and Darienzo           and others (1991), and Peterson (personal com-
                (in press) have shown that in Alsea Bay, abrupt         munication, 199 1) find that the vast majority        of
                land subsidence is the only Rely cause for the          tsunami deposits occur directly above buried
                buried marshes observed there. However, the ori-        marshes.
                gin of buried layers in other bays may still be            Another unresolved problem with the great
                questioned.                                             subduction earthquake hypothesis is the common
                   If we accept that the marshes do subside dur-        occurrence of uplifted marine terraces adjacent to
                ing earthquakes, we must assess the possibility         estuaries which contain buried marshes. Sea level
                that each estuary is responding to independent          has changed dramatically during the last few hun-
                movements on local faults rather than great sub-        dred thousand years, falling during ice ages when
                duction earthquakes that cause many estuaries to        water is tied up in glaciers, and rising between ice
                subside at the same time. Goldfinger and others         ages as glaciers melt. During each high stand of
                (1990) have studied faults on the continental shelf     sea level, wave action cuts a platform across
                and slope of Oregon and have identified dozens          coastal bedrock, which is then covered by marine
                of major faults which may have moved in geo-            sediments to form a distinct, flat marine ten-ace.
                logically recent times. Many of the estuaries           The most recent high stand was about 80,000
                where buried marshes occur appear to lie on these       years ago, and at many sites along the Oregon
                faults, raising the possibility of numerous local       and Washington coast this ten-ace is now several
                subsidence events. Further investigation is neces-      meters to tens of meters above modem sea level.
                sary to determine whether these faults are inde-        If sea level now is about the same as it was
                pendently responsible for marsh burial, but             80,000 years ago, these tenuces must have been
                several general observations suggest that they are      uplifted by earth movements. However, the up-
                not. First, at least a dozen estuaries between cen-     lifted terraces are often adjacent to estuaries in
                tral Oregon and central Washington subsided             which there is clear evidence of several meters of
                about 300 years ago (see below). If each subsid-        submergence in the last few thousand years. It is
                ence event was the result of an independent earth-      necessary to resolve the contradictory evidence
                quake, the implication is that over a dozen             for net uplift over the last 80,000 years and net
                occurred in the late 1600s, but none have oc-           submergence over the last 5,000 to 10,000 years.
                curred since the 1840s. There are so many estuar-          A final unresolved problem with the great sub-
                ies with relatively recent and frequent marsh           duction earthquake hypothesis is the apparent
                burials that we should have historical records of       lack of widespread evidence of liquefaction. Liq-
                marsh burial events if they are due to random           uefaction occurs when loose, water-saturated
                earthquakes on a dozen independent faults. In ad-       sand deposits are shaken strongly in an earth-
                dition, geologic mapping onshore, in some cases         quake. The sand becomes fluid, and a mixture of
                quite detailed, has yet to uncover evidence that        sand and water often erupts onto the ground sur-
                any of the offshore faults associated with estuar-      face through fissures. These sand fissures and
                ies has moved in the last few thousand years.           erupted sand piles are commonly observed in
                   Finally, almost every estuary has evidence of        many other areas of the world that have been
                tsunamis associated with one or more of the bur-        shaken by strong earthquakes. The presence of
                ied marsh layers. Peterson and Darienzo (in             such features in association with buried marsh
                press) have pointed out that if each estuary has an     horizons would strongly support the great earth-
                independent earthquake which generates a local          quake hypothesis. The widespread absence of liq-
                tsunami, there will be a tsunami deposit directly       uefaction features along the Oregon and
                above the subsided marsh in that estuary, and tsu-      Washington coast could suggest that whatever
                nami deposits at a variety of levels in adjacent        caused the marshes to subside did not involve

                                                                                                                              13







                            strong shaking. Widespread liquefaction features         even more of a problem. Radiocarbon ages date
                            have not been reported from the Oregon coast to          the time of death of the plant material, and
                            date; however, no systematic effort has been             samples taken from peats may have been dead on
                            made to locate them. In Washington, Atwater              the ground for tens or hundreds of years before
                            (personal communication, 199 1)) has found liq-          the marsh subsided. This error can be greatly re-
                            uefaction features associated with buried marshes        duced by dating material from trees rooted in the
                            at sites on the Copalis River. Peterson (personal        buried marsh that were presumably killed by the
                            communication, 199 1) has observed widespread            subsidence, but such trees are far less common
                            liquefaction on the Oregon coast in marine ter-          than peats. In general, at any site, it may not be
                            race sediments which are 80,000 years or more            possible to date the time of marsh subsidence any
                            old. I have observed similar features in old ma-         closer than plus or minus 100 to 200 years. This
                            rine ten-ace sediments in the Coos Bay area. The         means that we cannot necessarily distinguish be-
                            critical problem is to find liquefaction features in     tween events that occurred a day apart and events
                            sediments that are only a few thousand years old.        that occurred a few hundred years apait, and it
                            Clearly, a concerted effort must be made to estab-       may well be that the average time between earth-
                            lish whether or not liquefaction features are wide-      quakes is similar to or smaller than the best reso-
                            spread along the Oregon coast, and if they are           lution of radiocarbon dating.
                            not, the great earthquake hypothesis must be care-          The second dating technique is tree-ring dat-
                            fully re-examined.                                       ing, which is accomplished by compaiing the pat-
                                                                                     tems of annual growth rings in trees killed by
                            When is the Next Big One? The Big                        subsidence to those in living trees on adjacent up-
                            Question                                                 lands. This technique allows dating of the time of
                                                                                     death of the trees to within a decade, or often
                               If we accept for the time being that buried           within a few years (Atwater and Yamaguchi
                            marsh deposits in Oregon and Washington are              199 1). However, well-preserved trees are not
                            natural seismographic records, then the next step        present in many sites, and living trees are not old
                            is to determine how often, on average, the prehis-       enough to compare with buried marshes that are
                            toric earthquakes occurred. If it is possible to cal-    more than 1,000 years old. This technique is most
                            culate a reliable average time between events,           useful for looking at the most recent events.
                            then it is possible to calculate the probability that       A final problem in calculating the average time
                            the next event will occur in some given time             between earthquakes is the possibility that due to
                            frame. This technique has been widely applied in         conditions of sedimentation, timing, local cli-
                            other areas where there is a reasonably well-dated       mate, sea level fluctuations, and so on, not all
                            geologic record of prehistoric earthquakes.              earthquakes will make unambiguous buried
                               The time of burial of marshes in Oregon has           marsh horizons at all sites. This means that recur-
                            been dated by two techniques, each of which has          rence intervals estimated for any one site will be
                            significant drawbacks. Radiocarbon dating can be         based on a minimum number of events thought to
                            used to date plant material preserved in the buried      have occurred. If one or two events were not
                            marsh or forest peats. The technique is relatively       clearly recorded, then the resultant estimate of
                            fast and inexpensive, and dateable plant material        recurrence interval will underestimate the prob-
                            is abundant. Analytical errors inherent in the           ability of the next earthquake.
                            technique are typically plus or minus 50 to 100             The uncertainties associated with dating marsh
                            years, which is not significant for materials that       subsidence mean that a credible calculation of the
                            are several thousand years old, but is very sigpifi-     probability of the next earthquake is still not pos-
                            cant for materials that are only a few hundred           sible, even assuming that buried marshes repre-
                            years old. Calibrations for prehistoric variations       sent past earthquakes. The best we can do with
                            in radioactive carbon production introduce addi-         the radiocarbon numbers at this point is to take
                            tional uncertainty, and many relatively young            the reported ages at face value and treat the re-
                            samples correspond to several calendar dates             sulting estimates of recurrence intervals with a
                            when calibrated. The second source of error is           great deal of skepticism. An important result we

                            14







               can derive from this kind of analysis is not so         along the coast then becomes so short that we
               much which day to be out of town in order to            would expect to have a historical record of one.
               avoid the Big One, but a sense of how short an          The other important fact to note is that recurrence
               interval is possible between great earthquakes,         intervals from many sites are at least as short as
               and a reasonable estimate of when the last one          the time since the last event, within the limits of
               occurred.                                               radiocarbon en-or.
                  The most recent event is probably the best              We have a long way to go before we can quan-
               dated, because it is best exposed and because lo-       tify the likelihood of the next great earthquake,
               cally the radiocarbon dating can be checked with        but this event is not necessarily going to occur in
               tree-ring dating of cedar and spruce trees killed       some remote future. In fact, it is quite possible
               by marsh subsidence. Atwater and Yamaguchi              that the next big shake will happen in the near
               (1991) find that in southwest Washington, radio-        future. This possibility should be sufficient to
               carbon and tree-ring dating suggest that the most       cause emergency managers, land-use planners,
               recent subsidence occurred about 300 years ago.         and public officials of coastal communities to
               Peterson and others (199 1) report a range of ages      start looking at where they are vulnerable.
               for the most recent event in Oregon bays, with the
               youngest at 270, plus or minus 60 and the oldest        Where and How Big: What Can We
               at 550, plus or minus 70 years BP. Grant (written       Expect?
               communication, 199 1) reports the most recent
               subsidence in the Salmon River of 247, plus or             Estimates of the size and potential location of
               minus 25 years BP, and in the Nehalem. River,           future great subduction earthquakes also vary
               225, plus or minus 19 years BP. Adams (1990)            widely and are based on a limited understanding
               estimated the age of the most recent turbidite off-     of the structure of the CSZ. The size of futum
               shore at 300 years BP by studying the thickness         earthquakes will depend on the area of the locked
               of sediment layers on top of the turbidite. Most of     fault between the plates that moves. The location
               these dates are consistent with the more precise        of the earthquake will similarly depend on the
               tree-ring data indicating that the last great event     portion of the fault that moves.
               or set of events occurred in the late 1600s, but it        The area of the fault that moves depends on
               is not possible to distinguish between one great        the width of the locked portion of the fault and
               simultaneous event and several smaller events           the length of fault along the coast that fails. The
               scattered over decades.                                 total length of the CSZ is fairly well known, but
                  The average intervals between earthquakes            few researchers think that the entire 1000 km will
               calculated from this data must be treated skepti-       fail all at once. Instead, the CSZ is likely to break
               cally. Atwater (personal commui-dcation, 1991) is       in a series of relatively short segments. Geoscien-
               not sure that a significant return time can be cal-     fists can guess at the location of segment bound-
               culated, but points out that there have been either     aries but still cannot demonstrate where they lie.
               6 or 7 events in the last 3,500 years. This suggests    Segments may be as short as 100 kilometers or
               a nominal recurrence of 500 to 580 years.               the full 1,000 kilometers. Similarly, the width of
               Peterson and others (199 1) report average inter-       the locked portion of the fault strongly influences
               vals of 370 years for 4 events at Netarts Bay, 340      the possible size of an earthquake. The location of
               years for 3 intervals in Alsea Bay, and a regional      the locked zone also controls where the earth-
               average over I I events in Northern Oregon of           quakes can occur. There is little agreement on the
               330 to 340 years. Adams calculated an average of        likely width of the locked zone. In southern Or-
               590 years for 13 events, using the turbidite data.      egon, Clark and Carver (1991) proposed that the
               There is wide variability in this data, but two         locked zone might be as wide as 75 to 100 kilo-
               things are clear. If all of these events were due to    meters in southern Oregon. Peterson and others
               independent earthquakes on local structures, then       (199 1) present a model of the locked zone con-
               there have been tens of earthquakes in the last         strained by marsh subsidence data that is best fit
               few thousand years. The return interval between         by a 90-kilometer-wide locked zone. Blackwell
               subsidence-causing earthquakes somewhere                (199 1) proposes a locked zone as narrow as 20

                                                                                                                             15







                              kilometers based on thermal modelling. Accord-             portion of the coast around Newport to illustrate
                              ing to Pezzopane and others (199 1), geodetic data         specific potential hazard zones (figures 13 and
                              suggests that it may vary widely in width. A pair          14). DOGANH has published environmental geo-
                              of potential locked zones is shown in figure 12.           logy maps of almost all of the coast of Oregon.

                                                                                                        V




                                                                                      North                                           North

                              Figure 12. Example     Juan                                             Juan
                              source zones for
                              hypothetical
                              subduclion
                              earthquakes.
                              Example on right      de Fuca.                    American             d e  Fuca'.                  American
                              after Pezzopane and
                              others, 1991.
                              Example on left
                              after Weaver and          Plate                                            P I'a t e':
                              Shedlock, 1989.                                         Plate                                            Plate





                                 Using this range of possible lengths and widths         These maps can be used by trained professionals
                              of rupture zone, researchers have suggested maxi-          to make a first-order assessment of potential
                              mum CSZ earthquakes of from Mw 8.0                         earthquake hazards. For this report, the maps are
                              (Pezzopane and others 1991) to 9.1 (Rogers                 out of Bulletin 8 1, Environtnental Geology of
                              1988). Similarly, the portion of the fault that fails      Lincoln County (Schlicker and others 1973).
                              may either be entirely offshore or extend a few            Ground Shaking and Amplification
                              tens of kilometers onshore. In any case, coastal              The most widely experienced effect of an
                              Oregon will be uncomfortably close to any CSZ              earthquake is ground shaking, which is also typi-
                              earthquake, and even the most distant possible             cally responsible for the majority of earthquake
                              earthquake of the smallest likely size (8.0) will          damage. The strength of shaking at any site dur-
                              cause significant shaking and damage.                      ing an earthquake will depend on the size of the
                                                                                         earthquake, the distance of the site from the epi-
                              Effects of Great Earthquakes: Shake,                       center, and the nature of the geologic materials
                              Rattle, Roll, Slide, Slosh, and Slump                      under the site. Larger earthquakes produce stron-
                                 How would a major earthquake affect the Or-             ger ground shaking, but the strength of shaking
                              egon Coast? We still know too little about the Po-         dies off rapidly with distance from the epicenter.
                              tential size and location of earthquakes to make           To predict the strength of shaking at a given site,
                              quantitative estimates of the kinds of damage that         we need to know how large the earthquake will
                              might occur, but we can provide gross estimates.           be and where it will be centered, both currently
                              Damaging effects of earthquakes fall into two              impossible to know. A few general models of the
                              categories: (1) the direct effects of ground               strength of ground shaking have been made for
                              shaking, fault rupture, and coseismic subsidence           the Oregon coast. The strength of ground shaking
                              and (2) the secondary effects of tsunami, seiche,          is usually expressed as a fraction of the force of
                              settlement, liquefaction, and landsliding. In this         gravity. Levels above .2 acceleration of gravity
                              section, I describe the potential impact of each of        (g) are significant, and modem buildings in Or-
                              these hazards on the Oregon coast, using a                 egon are designed for.2 g. Pezzopane and others

                              16









                                                                                                        M,

                                                        20                                                                                             'n Rk



                                                   Tib%

                                             Moloch
                                             Beach
                                                   15   m;t
                                              207,                                            2:-
                                    R-@


                                                                                                                16

                                            9                                                                                                   0
                                                                                                                                                                   ID
                                           17      m
                           Ug@ u:Rg
                                                                                  fv
                 Yaquina He;ad
                                                                            NO
                              Tmcf
                                                   Tmd',



                                                        20-





                                                        15
                                                                                                                                                                            Figure 13.
                                                   Tmn                                                                                                                      Geologic nwp of
                                                                                                                                                             >0             the Newport area,
                                        Jumpott J                 4                                                                                                         Lincoln County,
                                                            fop*
                                                                                                                                                                            Oregon. After
                                                                                                                                                                            Schlicker ami
                                                   Beac                      Wg  S@
                                        NEWPOR                                                                                                                              others, 1973.
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       County, Oregon. After
       Schlicker and others,
       1973,

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                                18







                (199 1) suggest that peak horizontal accelerations         Coseismic Subsidence
                of .2 g to .4 g can occur along the coast. Cohee              As we saw earlier, the footprint that a great
                and others (1991) model a magnitude 8.1 subduc-            subduction earthquake makes on the land is a pat-
                tion zone earthquake and suggest that coastal Or-          tern of rapid subsidence or uplift of the land. This
                egon might experience . 14 g to .41 g of peak              movement, which takes place during the earth-
                horizontal acceleration. An additional threat              quake, is called coseismic movement. It is the
                unique to CSZ earthquakes is the unusually long            occurrence of coseismic subsidence along the Or-
                duration of shaking. The magnitude (Mw) 8.1                egon coast that is thought to be responsible for
                earthquake modelled by Cohee and others (1991)             the repeated burial of marshes, and a future great
                would cause strong shaking for over 45 seconds.            subduction earthquake would be likely to produce
                Damage increases dramatically as the duration of           similar effects. It is possible to estimate the
                shaking increases.                                         amount of coseismic subsidence at a marsh site
                   The ground motion levels discussed above are            by identifying the ecological zones represented
                for bedrock sites. The presence of thick soils, al-        by the successive layers and measuring the differ-
                luvial deposits, or soft rock over the bedrock can         ence in elevation between modem representatives
                greatly amplify the ground shaking, often by fac-          of those zones. Peterson and others (1991) have
                tors as high as six. In general, young (Quaternary)        made such estimates of the average coseismic
                deposits of sand, silt, and clay are most likely to        subsidence at three bays for the last four burial
                amplify ground shaking, although less frequently           events. They found 1.0 to 1.5 meters of subsid-
                they may actually reduce ground shaking. Figure            ence at Netarts Bay, .5 meter to 1.5 meters at
                15 is derived from figure 13, the geologic map             Alsea Bay, and 0 to .5 meter at the Siuslaw River.
                from DOGAMI Bulletin 91, and shows the areas               These are not dramatic amounts of subsidence
                covered by the geologic units labelled Qmt (Qua-           and are unlikely to cause large-scale flooding of
                ternary Miocene ten-ace) and Qal (Quaternary               coastal communities. However, this subsidence
                alluvium). The Qmt deposits are young marine               adds to the flooding by the subsequent tsunami
                terrace sand deposits, and the Qal deposits are            and causes increased flooding during stonns and
                young sand, silt, and gravel deposits lining the           accelerated coastal erosion.
                bays and river valleys. These units are most likely        Fault Rupture
                to amplify shaking, in contrast to the bedrock de-            As discussed in the section on crustal earth-
                posits present in the rest of the area. Therefore,         quakes, we know of few young faults on the coast
                for a preliminary assessment, these areas would            of Oregon. However, them are numerous offshore
                be considered more potentially hazardous, and              faults. These offshore faults appear to cut the sea-
                more refined hazard assessments would be fo-               floor and are therefore likely to have moved in
                cused there. The actual threat of ampfification can        geologically recent times. Ground rupture caused
                be modeled by computer techniques for a given              by movement of an offshore fault is not a great
                site, a procedure that might be appropriate for            problem because there is no development off-
                large structures or critical facilities like hospitals.    shore. Figure 16, derived from the geologic map
                   To illustrate the importance of soil amplifica-         in figure 13, shows several major west-northwest
                tion, we can look at the Mexico City earthquake            trending faults passing south of Yaquina Bay.
                of 1985. This earthquake, a magnitude (Mw) 8.1             These faults are very similar in trend to the geo-
                subduction zone megathrust event, was centered             logically young offshore faults, and there remains
                300 kilometers from Mexico City. Soft alluvium             a possibility that they may move during a great
                in the old lake beds on which the city is built am-        subduction earthquake or independently in a
                plified the shaking sufficiently to cause complete
                collapse of numerous modem structures engi-                smaller crustal earthquake. The likelihood is
                neered to withstand earthquakes. Similarly, the            probably remote, so again, this hazard might be
                portion of the Cypress Freeway structure that col-         of concern only in the siting and construction of
                lapsed in the 1989 Loma Prieta earthquake was              critical stiuctums. It is very expensive to engineer
                only that part built on soft bay mud.                      structures to tolerate fault rupture beneath their

                                                                                                                                 19


























                                 Figure 15. ExanWle
                                 wnplification
                                 0
                                     ortuni map.
                                  PP       ty
                                 Hatched areas are
                                 likely to shake most
                                 strongly in an
                                 earthquake because
                                 of loose Quaternary                                         . . . .. . ... .
                                                                                          . .. . .... .
                                 deposits.
                                                                                                 . . . . . . . . . . . .....
                                                                                                       q
                                                                                                   . ........ ...

                                                              . . . . . . . . . . . . . .

















                                 foundations, but it is relatively easy to site struc-           structures to tilt, sink or settle dramatically when
                                 tures well away from the potential rupture zone.                the underlying soil liquefies. Even more devastat-
                                 Liquefaction and Settlement                                     ing is the tendency for liquefied soil to flow to-
                                    Many geologically young sand and silt depos-                 wards free faces (such as river or bay banks) and
                                 its are relatively loose, meaning that the sand par-            down very gentle slopes. Mass movement of liq-
                                 ticles are not tightly packed together and them are             uefied or partly liquefied soils results in the most
                                 significant spaces between grains. When shaken                  spectacular of earthquake damage and is particu-
                                 by an earthquake, loose sand or silt can become                 larly devastating to coastal areas, damaging
                                 more compact, just as flour settles when shaken                 bridges, docks, and port facilities. Liquefaction
                                 in a measuring cup. If the sand is dry, ground                  also causes widespread faflure of buried pipes
                                 settlement occurs, which may locally be suffi-                  and cables, affecting fire fighting and emergency
                                 cient to damage structures. An even more de-                    communications after the event.
                                 structive situation exists when the sand is                        As with amplification, the tendency of any site
                                 saturated with water before the earthquake. The                 to liquefy in an earthquake can be estimated accu-
                                 settlement of the sand pressurizes the water in the             rately only with a detailed site-specific study. The
                                 spaces between grains, and the pressurized water                Qmt and Qal deposits are the only geologic mate-
                                 causes the sediment to liquefy. Because liquefied               rials in this area with any significant potential for
                                 sediment has very little strength, it is common for             liquefaction. Although they are widespread, these
                                                                                                 materials pose a threat only wheree they am

                                 20

























                                                                                                       Figure 16. Example
                                                                                                       fault rupture
                                                                                                       opportunity map.
                                                                                                       Heavy lines are
                                                                                                       mappedfaults.

















                                                                      7
                                                                        . ...... .
                ... ...... .. . . . .... .. .
                                                                              . . .......
                          . .... ...




                saturated with groundwater. Again, we can use           earthquake-induced landslides can occur up to
                the geology and environmental hazard maps for           200 kilometers from the epicenter of a magnitude
                the Newport area to roughly estimate the areas          8 earthquake. As with the amplification and liq-
                most susceptible to liquefaction, and thus narrow       uefaction hazards, detailed site studies are re-
                down the area where more specific studies are           quired to determine how likely a slope is to slide
                needed. Figure 17 shows areas likely to be sus-         in the event of a given earthquake. Again, it is
                ceptible to liquefaction. It is derived by over-        possible to use the information available in the
                laying areas of shallow ground water (depicted on       DOGAMI environmental hazard maps to outline
                the environmental geology map, figure 14) on            areas most likely to experience this hazard. Fig-
                areas of Qmt or Qal sands and silts (depicted on        ure 18 shows two types of landslide data derived
                the geologic map, figure 13).                           from the maps. Areas of existing landslides or
                Landslides                                              landslide topography are taken directly from the
                   One of the most common secondary hazards             environmental geology map (figure 14). These
                associated with earthquakes is earthquake-m-            areas may be reactivated in future earthquakes,
                duced landslides. Slopes which are stable under         particularly where they have been developed, cut
                ordinary conditions may be destabilized by the          by roads, or logged. Landslide-prone areas are
                strong shaking of an earthquake and begin to            derived by overlaying areas of mudstone bedrock
                move. Wilson and Keefer (1985) note that                from the geologic map (figure 13) on areas with
                                                                        slopes over 25% from the environmental geology

                                                                                                                          21



























                                                                          @Z


                             Figure 17. Example
                             liquefaction opportunity
                             map. Hatched zones
                             have both loose sands
                             and shallow
                             groundwater.






                                                                               . .........
                                                                         ...... .....
                                                                                                  . .. ....
















                                                                                                                         . . . . . . . . . ..





                             map (figure 14). These areas are the most likely          hazards are likely to occur in the event of a sub-
                             to have new landslides in an earthquake. In addi-         duction zone earthquake, but only seiches are
                             tion, areas of rapid sea cliff erosion or riverbank       likely to occur in a crustal or intraplate earth-
                             erosion may be susceptible to earthquake-induced          quake.
                             landsliding. In all cases, extensive development,            The extent of inundation caused by a seiche in
                             logging, forest fires, or road building may in-           any body of water will depend on the strength of
                             crease the likelihood of earthquake-induced land-         ground shaking at the site. It will also depend on
                             slides because of changes in drainage and                 the degree of similarity between the natural pe-
                             stability of the slopes.                                  riod of oscillation of the body of water and the
                             Tsunami and Seiche                                        period of shaking of the earthquake. This makes
                                The final class of secondary earthquake hazard         estimation of seiche hazards extremely difficult,
                             is mass movements of water which may inundate             because the periods of shaking of earthquakes are
                             shoreline areas. In a seiche, the water in a rela-        quite variable. Sophisticated computer modelling
                             tively small body of water, like a lake or bay,           can put rough limits on the maximum seiche nm-
                                                                                       up, but this technique is relatively expensive.
                                                                                                             ey_iogm'@







                             sloshes from bank to bank, just like a full coffee           Tsunamis are great waves produced by vertical
                             cup on a bumped table. A tsunami occurs when a            motion of large portions of the seafloor. The
                             large area of the seafloor moves, displacing a            waves travel at speeds of several hundred kilome-
                             huge amount of water in the ocean. Both of these          ters per hour in the open ocean, where they may

                             22














                                                Areas of landslide-prone
                                                mudstone with slope >25%


                                                       Existing landslides or
                                                        landslide topography.






                                                                                                      Figure 18. Example
                                                                                                      earthquake-induced
                                                                                                      landslide opportunity
                                                                                                      map.


                              . . . .. . .










                                            .....    . . . . . .
                                                   ....................................














                                                                  11 . ... . . . . .





               be only a fraction of a meter high. When a tsu-       an earthquake on the CSZ would arrive without
               nami wave approaches shore, it begins to slow         any warning other than the earthquake itself.
               down and get higher, and what began as a wave            Without knowing the exact size and location
               only a half a meter high on the open ocean may        of future subduction zone earthquakes, it is diffi-
               be several meters high when it reaches shore. The     cult to predict tsunami run-up heights for the Or-
               maximum elevation above sea level that the tsu-       egon coast. There are, however, several crude
               narni reaches is called the run-up. The area cov-     approaches available to get a general feel for the
               ered by the tsunami is the inundation. Tsunamis       possible magnitude of locally generated tsunamis.
               are not likely to be generated by crustal or          The first approach is to look at the "tsunami"
               intraplate earthquakes, because these types of        sand deposits associated with buried marshes
               earthquakes are relatively small and do not in-       along the coast. This has been done by Peterson
               volve vertical movements of the seafloor. Sub-        and others (1991 a), who produced maps of the
               duction zone earthquakes, on the other hand, are      areas thought to have been inundated by the tsu-
               very large, cause large vertical movements of the     namis that followed past subduction earthquakes.
               seafloor, and usually cause tsunamis. There is        Unfortunately, all the tsunami deposits are pre-
               currently a warning system in place to alert resi-    served in the modem estuaries, so these maps
               dents of the Oregon coast to the approach of tsu-     show only the minimum area covered by the tsu-
               namis generated in Alaskan, Chilean, or Japanese      narni. Tsunami sands are not preserved if they are
               subduction zones, but the tsunami generated by        deposited on slopes above the bay, so we cannot

                                                                                                                         23







                                    use this technique to determine the maximum wa-                tsunami height at the latitude of Astoria. Again,
                                    ter level, only the minimum. Peterson and others               this model gives wave height only at a water
                                    (1991 a) found prehistoric tsunami sands at least 2            depth of 50 meters and does not carry the wave
                                    kilometers (and possibly 18 kilometers) up                     onshore. The Baptista and others model suggests
                                    Yaquina Bay.                                                   that a wave about 7 meters high would be likely
                                     The other approaches to tsunami height is                     from an average subduction zone earthquake. The
                                    computer modeling. The modeling of waves trav-                 wave height in this model is very dependent on
                                    eling in water is fairly straightforward, but it is            variables that are still poorly known, so the wave
                                    extremely complex to model how the wave be-                    height may not be reliable. The arrival time of the
                                    haves when it enters shallow water (less than 50               tsunami is much less variable, however, and un-
                                    meters) and interacts with the irregular floor of              derscores the unique threat associated with lo-
                                    the shallow sea. It is even more complicated to                cally generated tsunamis. The tsunami crest in the
                                    model how the wave behaves in estuaries. Two                   model reaches the coast 20 to 30 minutes after the
                                    attempts have been made to model a locally gen-                earthquake. This is not enough time for an official
                                    erated tsunami caused by a subduction zone                     warning to be issued, so all coastal residents
                                    earthquake. Hebenstreit (1988) modeled the tsu-                should consider strong ground shaking as a natu-
                                    naini likely to accompany a magnitude 9.1 (Mw)                 ral tsunami warning and should seek high ground
                                    earthquake (figure 19). His model shows ex-                    immediately.
                                    pected wave height along the Oregon coast at                      The actual height above sea level reached by
                                    points a few kilometers offshore, thereby side-                any tsunami will depend on many local factors,
                                    stepping the shallow-water problem. Clearly,                   including the offshore wave height, the shape of
                                    these wave heights, locally as much as 12 meters,              the shore or estuary, the normal tidal stage at the
                                    represent a serious threat. Baptista and others                time, and the amount of coseismic subsidence. It
                                    (199 1) have produced a simple model as a pre-                 is not unreasonable for many parts of the Oregon
                                    lude to a more complete model. Their initial                   coast to expect tsunami run-up of 5 to 10 meters,
                                    model is designed to test the sensitivity of tsu-              with inundation extending several kilometers up
                                    nami height to various factors and only estimates              many estuaries.


                                                                                                                                         Max height W
                                                      Cascadia Plate (South segment)                                                   0.0         6.0             12.0

                                                                                                                      0



          Figure 19. Computer
          model of local Isunami in
          the Pacific Northwest                                                                                             0
          from a hypothetical Mw
          9.1 subduction
          earthquake. Right hand                    j
          figure shows the pattern                                                                             0
                                            @D
          of wave elevationfor all          t
          recording points; the             E_
          solid line is the average
          for all points. Wave
          heights arefor points
          offshore; they cannot be
          used to estimate coastal
          run-up or inundation.
          From Hebenstreit, 1988.                 I_                                                                          0
                                                                                                 100
                                                              Af                              0  Q
                                                                     (D0


                                                   130         129         128         127         126         125         124         123
                                                                                      LONGITUDE



                                    24






                Conclusions: Should We All Move to                        ards can be reduced in communities by increasing
                Nebraska?                                                 public awareness of the hazard and by protecting
                                                                          lifelines and structures. The first is relatively in-
                     Where does all of this uncertain science leave       expensive, and can save many lives. Community
                the residents and decision makers of Oregon's             groups, the Red Cross, and others can help to
                coastal communities? Some may think that we               educate the community about earthquake and
                must evacuate the coast forever; others will think        general disaster preparedness. Protecting the in-
                we can continue to develop without regard to              frastructure is economical over the long run, as
                seismic hazards. The truth, of course, lies in be-        long as it is integrated into long-range building
                tween. Let's look at a few key facts.                     and land-use plans. Hazardous buildings will
                     In 150 years or so of our history, there has         probably not get fixed, but they should be re-
                     been no earthquake damage on the coast, yet          placed by earthquake-resistant structures when
                     there has been abundant damage caused by             their natural life is over. Similarly, facilities sited
                     mundane hazards like storms, coastal erosion,        in hazard zones probably won't get moved, but
                     and landslides.                                      their replacements should be sited properly. Plan-
                                                                          ning carefully, identifying hazard zones, and con-
                                                                          sidering potential earthquake safety as an element
                     The best geologic data now available strongly        -
                     suggests, but cannot prove, that most of the         in any development project will lead in the long
                     coast is susceptible to large damaging earth-        run to a much more earthquake-resistant Oregon
                     quakes. These events are certainly rare on           coast. Odds are that we have decades to prepare.
                     human time scales, but could occur at any            We should not squander that opportunity.
                     time.

                     The naturul geologic makeup of the coast             References
                     makes it prone to a variety of earthquake haz-       Adams, J., 1984, Active deformation of the
                     ards, and any large earthquake is likely to              Pacific Northwest continental margin: Tecton-
                     cause a large amount of damage.                          ics 3:449-472.
                                                                          Adams, J., 1990, Paleoseismicity of the Cascadia
                     It is possible now to make a broad assess-               subduction zone: Evidence from tuibidites off
                     ment of hazard zones in which individual                 the Oregon-Washington margin: Tectonics
                     sites need to be investigated in more detail.            9:569-583.
                                                                          Ando, M., and Balazs, E.I., 1979, Geodetic
                ï¿½    Lifelines in Oregon coastal communities are              evidence for aseismic subduction of the Juan
                     likely to be severely impaired in the event of           de Fuca plate: Journal of Geophysical Re-
                     large earthquakes, affecting emergency re-               search 84:3023-3027.
                     sponse operations.                                   Atwater, B.F., 1987, Evidence for great Holocene
                                                                              earthquakes along the outer coast of Washing-
                ï¿½    The long-terrn economic impact of a large                ton State: Science 237:942-944.
                     earthquake may destroy communities more              Atwater, B.F., 1989, Geologic studies for seismic
                     thoroughly than the ground shaking.                      zonation of the Puget Sound lowland. U.S.
                                                                              Geological Survey Open-File Report 89-453, p
                ï¿½    No community can afford to "earthquake                   520.
                     proof' all of its lifelines and economic infra-      Atwater, B.F., and Yamaguchi, D.K., 1991,
                     structure in the short run.                              Sudden, probably coseismic submergence of
                                                                              Holocene trees and grass in coastal Washing-
                     What should be done, given these facts? Cer-             ton State: Geology 19:706-709.
                tainly we need more research to answer many of            Baptista, A.M., Remedio, J.M., and Peterson,
                the uncertainties about the earthquake threat, but            C.D., 1991, Sensitivity Analysis to tsunami
                we know enough to begin to act. Earthquake haz-               propagation on the Pacific Northwest coast:

                                                                                                                                   25







                                final technical progress report to the Oregon        Heaton, T.H., and Snavely, P.D., Jr., 1985,
                                Department of Geology and Mineral Indus-                Possible tsunami along the northwestern coast
                                tries, Portland, Oregon.                                of the United States inferred from Indian
                             Blackwell, D., 199 1, Oral presentation at 2nd             traditions. Bulletin of the Seismological
                                workshop on Oregon earthquake sources,                  Society of America 75:1455-1460.
                                Corvallis, Oregon, April 18, 1991.                   Hebenstreit, G.T., 1988, Local Tsunami hazard
                             Byrne, D.E., Davis, D.M., and Sykes, L.R., 1988,           assessment for the Juan de Fuca plate area:
                                Loci and maximum size of thrust earthquakes             Report to U.S. Geological Survey, Contract
                                and the mechanics of the shallow region of              14-08-001-GI346, by Science Applications
                                subduction zones: Tectonics 7:833-857.                  International Corporation, McLean VA.
                             Carver, G.A., 199 1, Oral presentation at 2nd           Jacobson, R.S., 1986, Map of Oregon Seismicity,
                                workshop on Oregon earthquake sources,                  1841-1986: State of Oregon Department of
                                Corvallis, Oregon, April 18, 1991.                      Geology and Mineral Industries GMS 49.
                             Clark, S.H., and Carver, G.A., 1991, Oral               Johnson, A.G., and Scofield, D.H., 199 1, Reas-
                                presentation at 2nd workshop on Oregon                  sessment of the seismic hazard for the State of
                                earthquake sources, Corvallis, Oregon, April            Oregon: Preliminary report to the Oregon
                                18,1991.                                                Department of Geology and Mineral Industries
                             Cohee, B.P., Somerville, P.G., and Abrahamson,             (DOGAMI).
                                N.A., 1990, Simulated ground motions for             Ludwin, R.S., Weaver, C.S., and Crosson, R.S.,
                                hypothesized Mw 8 subduction earthquakes in             1989, Seismicity of Oregon and Washington:
                                Washington and Oregon: Bulletin of the                  In Slemmons, D.B., Engdahl, E.R., Blackwell,
                                Seismological Society of America, Vol. 81,              D., Schwartz, D., and Zoback, M., eds.
                                No. 1.                                                  Neotectonics of North America, Geological
                             Darienzo, M.E., and Peterson, C.D., 1988,                  Society of America Decade of North Ameri-
                                Coastal Neotectonic field trip guide for Netarts        can Geology, Volume GSMV-1. (Preprint).
                                Bay, Oregon: Oregon Geology 50:99-106.               Mchielly, G.W., and Kelsey, H.M., 1990, Later
                             Darienzo, M.E., and Peterson, C.D., 1990,                  Quaternary, tectonic deformation in the Cape
                                Episodic tectonic subsidence of late Holocene           Arago-Bandon region of coastal Oregon as
                                salt marshes, Northern Oregon central                   deduced from wave-cut platforms: Journal of
                                Cascadia margin: Tectonics 9:1-22.                      Geophysical Research 95:6699-6713.
                             Goldfinger, C., Mackay, M.C., Kulm, L.D., and           Nelson, A.R., and Personius, S.P., in press. The
                                Yeats, R.S., 1990, Neotectonics and possible            potential for great earthquakes in Oregon and
                                segmentation of the Juan De Fuca plate and              Washington: an overview of recent coastal
                                                                                        geologic studies and their bearing on segmen-
                                Cascadia subduction zone off central Oregon:            tation of Holocene ruptures, central Cascadia
                                EOS, Transactions of the American Geophysi-             subduction zone; From A.M. Rogers, W.J.
                                cal Union 71:1580.                                      Kockelman, G. Priest, and T.J. Walsh, eds.,
                             Grant, W.C., and McLaren, D.D., 1987, Evidence             Assessing and reducing earthquake hazards in
                                for Holocene subduction earthquakes along the           the Pacific Northwest, U.S. Geological Survey
                                Northern Oregon coast: EOS 68:1239.                     Professional Paper.
                             Griggs, G.B., and Kulm, L.D., 1970, Sedimenta- Noson, L.L., Qarnar, A., and Thorsen, G.W.,
                                tion on the Cascadia deep-sea channel:                  1988, Washington State Earthquake Hazards:
                                Geological Society of America Bulletin                  Washington Division of Geology and Earth
                                81:1361-1384.                                           Resources Information Circular 85.
                             Harbert, W., 199 1, Late Neogene relative mo-           Peterson, C.D., and Darienzo, M.E., 1988,
                                tions of the Pacific and North America plates:          Coastal Neotectonic Field trip guide for
                                Tectonics 10: 1- 15.                                    Netarts Bay, Oregon: Oregon Geology 50:99-
                             Heaton, T.H., and Kanamori, H., 1984, Seismic              106.
                                potential associated with subduction in the          Peterson, C.D., and Darienzo, M.E., in press.
                                northwestern United States: Bulletin of the             Discrimination of climatic, oceanic and
                                Seismological Society of America 74:933-94 1.           tectonic forcing of marsh burial events from

                             26







                  Alsea Bay, Oregon, U.S.A.: From A.M.              Schlicker, H.G., Deacon, R.J., Beaulieu, J.D., and
                  Rogers, W.J. Kockelman, G. Priest, and T.J.          Olcott, G.W., 1973, Environmental Geology
                  Walsh, eds., Assessing and reducing earth-           of Lincoln County, Oregon: Oregon Depart-
                  quake hazards in the Pacific Northwest, U.S.         ment of Geology and Mineral Industries
                  Geological Survey Professional Paper.                Bulletin 8 1.
               Peterson, C.D., Daxienzo, M.E., and Clough, C.,      Vincent, P., 1989, Geodetic deformation of the
                  1991, Recurrence intervals of coseismic              Oregon Cascadia margin: (M.S. Thesis)
                  subsidence events in Northern Oregon bays of         Eugene, Oregon, University of Oregon.
                  the Cascadia margin. Final Technical Report       Weaver, C.S., and Baker, G.E., 1988, Geometry
                  to the Oregon Department of Geology and              of the Juan de Fuca Plate beneath Washington
                  Mineral Industries (DOGAW, September 9,              and Northern Oregon from seismicity: Bulletin
                  1991.                                                of the Seismological Society of America
               Peterson. C.D., Baptista, A.M., and Darienzo,           78:264-275.
                  M.E., 199 1 a, Paleo-Tsunarni evidence in         Weaver, C.S., and Shedlock, K.M., 1989,
                  northern Oregon bays of the central Cascadia         Potential subduction, probable intraplate and
                  margin: Final Technical Progress Report to the       known crustal earthquake source areas in the
                  Oregon Department of Geology and Mineral             Cascadia subduction zone: In W.W. Hays, ed.
                  Industries, Portland, Oregon.                        Proceedings of Conference XLVIII, 3rd
               Pezzopane, S.K., Weldon, R.J., Johnson, A.G.,           Annual Workshop on Earthquake Hazards in
                  and Scofield, D.H., 199 1, Seismic Accelera-         the Puget Sound, Portland Area. U.S. Geologi-
                  tion maps from Quaternary Faults and Historic        cal Survey Open File Report 89-465.
                  Seismicity in Oregon: Final technical progress Weldon, R.J., 1991, Active tectonic studies in the
                  report to the Oregon Department of Geology           United States, 1987-1990: In U.S. National
                  and Mineral Industries, Portland, Oregon.            Report to Intemational Union of Geodesy and
               Platker, G., 1972, Alaskan Earthquake of 1964           Geophysics 1987-1990, Contributions in
                  and Chilean Earthquake of 1960: Implications         Geophysics, American Geophysical Union,
                  for Arc Tectonics: Journal of Geophysical            pp. 890-906.
                  Research 77:901-925.                              Wilson, R.C., and Keefer, D.K., 1985, Predicting
               Riddihough, R., 1984, Recent movements of the           areal limits of earthquake-induced landsliding:
                  Juan de Fuca plate system: Journal of Geo-           In J.I. Ziony, ed. Evaluating earthquake
                  physical Research, 89:6980-6994.                     hazards in the Los Angeles Region-An earth
               Rogers, G.C., 1988, An assessment of the                science perspective. U.S. Geological Survey
                  megaffirust earthquake potential of the              Professional Paper 1360.
                  Cascadia subduction zone: Canadian Journal        Woodward, J., 1990, Paleoseismicity and the
                  of Earth Sciences 25:844-852.                        archaeological record: Areas of investigation
               Savage, J.C., and Lisowski, M., 1991, Strain            on the northern Oregon coast: Oregon Geol-
                  measurements and potential for a great               ogy 52:57-65.
                  subduction earthquake off Oregon and Wash-
                  ington: Science 252:101-103.















                                                                                                                      27





             MEW             SEismic HAZARDS ON THE OREGON COAST-
                             A RESPONSE

                             Richard W. Rinne
                             RZA Engineers, Portland, Oregon


        PACIFIC
        NORTHWEST            I am going to limit my discussion to things that I       (eastward) margin of the terrace deposits has
        COASTAL
        EARTHQUAKE,          actually have knowledge of, namely landsliding.          pulled away from the underlying bedrock, creat-
        TSUNAMI, AND            In my opinion, landsliding holds the most po-         ing a new drainage path. One could also imply
        LANDSLIDE            tential for liability and is the most visible hazard     from figure 2 that the Astoria and Nye mudstone
        HAZARDS
                             along the Oregon coast, especially between New-          formations could have undergone similar
                             port and Lincoln City. This is not to say that           movements.
                             landsliding is confined to this portion of the coast;       These terrace deposits were apparently once
                             rather, it is one of the most populated areas and        uniform sand or poorly indurated sandstone that
                             subjected to more human activity than most other         rested on seaward-sloping or dipping mudstones.
                             areas.                                                   From my experience, when excavating the terrace
                                Madin has noted that the most slide-prone ar-         deposits one finds that they are highly fractured
                             eas are mudstone bedrock and slopes over 25%             and contain large volumes of water. Normal
                             and areas of rapid sea cliff erosion or riverbank        coastal erosion and saturation by heavy rain-
                             erosion. I would add ten-ace deposits overlying          storms can cause, and has caused, sections to
                             seaward-dipping mudstone with slopes as flat as          break off and slide onto the beach. The active
                             10 degrees. Typically, the landsliding occurs            sliding is usually within one or two hundred yards
                             within a few hundred feet of the beachline and           of the beach. My concern is that this pattern of
                             during or after heavy or prolonged rainfall. Se-         fracturing (figure 1) continues many hundreds of
                             vere storms that result in pounding and erosion of       yards inland. Observations also show that the
                             the sea cliff compound the land movement.                fractures farther from the shoreline do not appear
                                My area of concern is landsliding connected to        to show any recent movement.
                             the subduction, or severe crustal quake. From my            Figure 3 depicts a possible sequence of events
                             observations of the morphology of the marine             without specific ages or intervals.
                             terrace deposits up and down the Oregon coast,              This phenomenon could possibly contain a
                             abnormal drainage patterns appear to be com-             geologic record in the form of Carbon-14 from
                             mon. Erosion of the Coast Range and nearshore            buried organics or tree rings (if any old enough
                             sediments should result in drainage ways perpen-         still exist) in the base of the ravines. Assuming
                             dicular to the coast. Seemingly more often than          that all of the fractures did not occur simulta-
                             not, the drainages are deflected at the margins of,      neously, different ages may be established for dif-
                             or within, the terrace deposits, and for variable        ferent events. At the very worst, a most recent
                             distances they pamllel the shorelines, as shown          event may be,isolated.
                             on the contour map example used for figure 1.               In summary, I feel that the research is moving
                                Figure 2 is the same map as figure I with geo-        steadily forward. This is serious business. I urge
                             logic units delineated from the mapping for              the researchers to avoid searching for data to fit
                             DOGANU Bulletin 81 (admittedly very broad and            preconceived notions (one set of en-ors can mean
                             general). Assuming that the terrace deposits are         hundreds of years for recurrence intervals).
                             more erodible than the underlying mudstone bed-          Coastal governments should not panic; the prob-
                             rock units, one would think that the erosional           ability for disaster was the same in the last decade
                             channels would continue straight toward the              as it will be in the next.
                             beach. An argument could be made that the upper




                             28





                                                                         t 4

                                                                           N







                                                              N&-
                                                                                                        41,


                                    AGE,
                                          r



                                                 Tension Cracks?



                   I     rv
                         CD






                           ill X.
                         (Ilk                  NV









                                                                                                                             n

                                                                                                                         0 GO










                  Figure 1.





                                                                                                                                      29














                                                                                     14  A k
                                                                    _A\l.             mt



                                                                 qs







                                                                                                                       a       mn







                                                                     amt












                                                                                                                      o
                                                                                                                      On   00
                                                                                                                         n Do










                         Figure 2.






                              30











                     A                                                   Qmnt

                                                                                                 -Tma/Tmn

                         Sea Level








                     B                                       Qmnt
                     Sea Levell                                                                  Tma/Tmn






                     C                                                Qmnt
                     Sea Level                                                                   Tma[Tmn







                     D                                   Qmnt
                     Sea Level                               d-                                  Trnafrmn




                Figure 3.
                A .  Uplifted terrace deposits in equilibrium. No disturbance.
                B.   Subduction quake. Terrace deposits move along bedrock surface, creating fractures parallel to the shoreline. Note
                     movement into zone of maximum erosion potential and parallel to the shoreline. Note movement into zone of
                     maximum erosion potential and downwarping.
                C.   Long period of quiescence (perhaps today?). Note that beach erosion has moved terrace deposits back to sea levell
                     bedrock contact. Nearshore landsliding is continual as the result of wave undercutting. Ravine slopes reaching
                     natural angle of repose.
                D.   Subduction quake (tomorrow?). Terrace deposits again move into zone of maximum erosion. Destruction of structures
                     on marine terrace deposits. Ravines open up again.
                                                             ow





































































                                                                                                                           31






            SOME              COMMENTS ON PAPER BY IAN MADIN

                              Raimnar Bard
                              Clatsop-Tillamook Intergovermnental Council



                                                                                     as                     s/F MA
                              How do we plan for a catastrophic event that h            2. Building Code E
       PACEFIC                a low probability of occurring at any given time            There is a conflict between FEMA flood regu-
       NORTHWEST
       COASTAL                but that, when it does occur, will have enormous         lations, which require the construction of piling-
       EARTHQUAKE,            consequences? At the conclusion of his paper, Ian        supported buildings in coastal high-hazard areas,
       TSUNAMI, AND
       LANDSLIDE              Madin suggests a number of steps various parties         and the poor performance of such structures in an
       HAZARDS                should ii-ftiate in light of our knowledge about         earthquake. Is there some way to reconcile this
                              earthquakes in subduction zones. I agree with            conflict?
                              their general direction and offer the following ad-         The same conflict exists where pile-supported
                              ditional comments.                                       structures have been built in filled estuaries and
                                                                                       flood plains. Much of Cannon Beach's downtown
                              Emergency Planning                                       is located in a filled wetland, and I suspect this is
                                                                                       not uncommon for other coastal towns located on
                                The first step in emergency planning is to in-         estuaries.
                              crease the level of public awareness. Most Cali-
                              fornians know about the San Andreas fault. But
                              how many Oregonians are aware of the potential           Land Use Planning
                              for a devastating earthquake in their state?             1. Relocation of Threatened Structures
                                We can learn from public information cam-                 It will be difficult to relocate a public facility
                              paigns in California and perhaps those in the            that is currently in an area at high risk from tsuna-
                              south, where officials are used to dealing with          mis until that facility is totally worn out. An ex-
                              hurricanes. This is an area in which the Federal         ample of such a structure is the Cannon Beach
                              Emergency Management Act (FEMA) should be                grade school, which is located on the Ecola Creek
                              doing a lot more.                                        estuary, an area extremely susceptible to tsunami
                                Any public information campaign will be                hazard.
                              complicated by the large number of tourists an
                              visitors in coastal communities. How can we              2. Planning for Tsunan-d Hazard
                              reach Us group effectively?                                 Present FEMA mapping and regulations do
                                                                                       not. consider tsunami hazards, either from a dis-
                              Buildings                                                tant earthquake or from one in the subduction
                                                                                       zone. Should they? Is it technically feasible to
                              1. Reinforcing Public Buildings                          prepare for a tsunami? If so, what might be the
                                Ideally, public facilities should be retrofitted to    implications of incorporating tsunami planning
                              withstand earthquakes. I agree with Madin's con-         into the regulations, including its effect on insur-
                              clusion that little will occur. With budgets lim-        ance rates?
                              ited, such improvements are likely to be a very             The fact that a tsunami wave could reach 10
                              low priority. Cannon Beach had some experience           meters or more does not leave much room for
                              with this last year. The city hall is of masonry and     land use planning in many communities. For ex-
                              would not be safe in an earthquake. For Us rea-          ample, in Cannon Beach, the elevation of down-
                              son, a consultant had recommended extensive              town is 12 feet mean sea level (MSL). The area
                              repairs. However, after lengthy discussions of the       is protected by a dike with a height of 20 to 25
                              situation, the city council voted to make only           feet MSL. Many of the city's oceanfront areas
                              minor repairs.                                           have a height of less than 30 feet MSL.


                              32






                CATASTROPHIC COASTAL HAZARDS IN THE                                                                                  MEW
                CASCADIA MARGIN U.S. PACIFIC NORTHWEST
                Curt Peterson                                                                                                     %
                                                                                                                                     'A
                Geology Department, Portland State University
                George Priest                                                                                                   PACIFIC
                Oregon Department of Geology and Mineral Industries                                                             NORTHWEST
                                                                                                                                COASTAL
                                                                                                                                EARTHQUAKE,
                                                                                                                                TSUNAMI, AND
                After decades of debate, scientists now believe           In addition to earthquake hazards, the cata-          LANDSLIDE
                that the Cascadia subduction zone, encompassing         strophic responses of some PNW beaches to the           HAZARDS
                the Pacific Northwest (PNW) coastal zone, is            anomalous storm conditions of the 1982-83 El
                coseismic, that is, predisposed to earthquakes.         Nifio event (Komar 1986; Tuttle 1987) have
                Preliistoric earthquakes of potentially very large      clearly shown the susceptibility of the beaches to
                magnitude (+8.5 Mw) are implied by past epi-            extreme interannual climatic events. Sustained
                sodes of abrupt coastal subsidence, tsunami inun-       beach erosion, sand dune accretion, or coastal
                dation, and sediment liquefaction (table 1;             flooding were experienced in many PNW coastal
                Atwater 1987; Reinhart and Bourgeois 1989;              zone beaches following the longshore redistribu-
                Darienzo and Peterson 1990; Vick 1988; Peterson         tion of beach sands during the 1982-83 winter
                et al. 199 1 a; Carver, pers. comm.). The prehis-       period. Some beaches experienced northward
                toric subduction zone earthquakes are estimated         sand displacements of 5 to 10 million cubic
                to have taken place at intervals of between 300         meters, over multikilometer distances, for a dura-
                and 600 years, with the last event occurring about      tion of several years (Peterson et al. 1990). 'Me
                300 years ago.                                          northward shift in beach sand resulted from an
                   While earthquake sources, magnitudes, and            unusually oblique approach of winter storm
                recurrence intervals in the Cascadia margin are         waves associated with anomalously low latitudes
                currently being investigated (Shedlock and              of North Pacific storm centers in 1982-83. The
                Weaver 1991) little is being done to establish          delayed return of beach sand to the south (1986
                site-specific risks from the collateral earthquake      and 1987) followed a two-year period of high-
                effects. Locally, these effects can include uncon-      latitude winter storms (1984 and 1985) that were
                solidated sediment liquefaction, coastal land-          unable to mobilize the northward displaced sand
                slides, tsunami inundation, and persistent              (Peterson et al. 1992). The several years follow-
                shoreline subsidence and related flooding. The          ing the 1982-83 El Niflo appear to be the most
                magnitude of coastal subsidence (zero to two            widespread erosional period in the PNW coastal
                meters relative sea level rise) could vary region-      zone during the last several decades.
                ally, producing extensive beach erosion and se-            Locally, the multiyear redistribution of littoral
                vere seasonal flooding in bays and fidal-river          sand (1) stripped beaches to underlying bedrock,
                flood plains. Beach retreat might shift some            (2) exposed sea cliffs and foredunes to direct
                shorelines landward by as much as 100 meters.           wave attack, or (3) caused the rapid growth of
                We estimate that as much as 90 percent of the           eolian dune fields (dunes caused by wind). The
                present wetlands and low pastures in some bays          presence of jetties, for example those at
                will be submerged following the next subsidence         Humboldt Bay and at the mouths of the Siuslaw,
                event. For the most part, PNW coastal planners at       Yaquina, and Columbia rivers, might have con-
                present have little or no site-specific data with       tributed to the post-El Nifto effects of local beach
                which to address concerns about these collateral        erosion. Furthermore, the long-term effects of sea
                seismic hazards.                                        walls, dune stabilization, and offshore dredge




                                                                                                                             33









                                            Locality                        Abrupt Subsidence                Tsunarni            Liquefaction

                                            Neah Bay, WA                                    X*
                                            Kalaloch, WA                                    X                                               X
                                            Copalis, WA                                     X*                         X*                   X*
                                            Grays Harbor, WA                                X*                         X*
                                            Willapa Bay, WA                                 X*                         X*                   X
                                            Seaside, OR                                     X                          X
                                            Cannon Beach, OR                                X                          ?
                                            Nehalem, OR                                     X**                        X**
                Table 1. Sites              Tillamook Bay, OR                               X                          ?
                showing possible            Netarts, OR                                     X                          X                    X
                evidence of                 Pacific City, OR                                X                          X                    X
                Cascadia margin             Neskowin, OR                                    X
                Paleoseismicily in                                                          X**                        X**
                Late Holocene and           Lincoln, City, OR                                                                               X
                Late Pleistocene            Gleneden Beach, OR                                                                              X
                coastal deposits.           Newport, OR                                     X                          X                    X
                Data compiled in
                September 1991.             Waldport, OR                                    X                          X
                                            Florence, OR
                                            Reedsport, OR                                   X
                                            Coos Bay, OR                                    X***                                            X
                                            Bandon, OR                                      X                          ?                    X
                                            Langlois, OR                                                                                    X
                                            Port Orford, OR                                                                                 X
                                            Gold Beach, OR                                                                                  X
                                            Arcata, CA                                      X****                                           X****
                                            Eureka, CA                                      X****                                           X****


                                            Published and unpublished data from PSU Geology Department and other
                                            sources listed below:
                                            *Pers. Comm., B. Atwater, USGS and J. Bourgeois, UW
                                            **Pets. Comm., W. Grant, USGS
                                            ***Pers. Comm., A. Nelson, USGS
                                            ****Pers. Comm., G. Carver, HSU
                                            ? Features tentatively identified.



                                 disposal on littoral sand supply in the PNW                         In addressing these newly identified coastal
                                 coastal zone have not been quantitatively evalu-                hazards, it is important to recognize the diversity
                                 ated. Of particular concern are the additive im-                of shoreline conditions and associated hazard
                                 pacts of (1) extreme changes in stoim wave                      susceptibilities in the PNW coastal zone. For ex-
                                 climate, (2) physical restrictions to longshore                 ample, the open ocean shoreline from the Juan de
                                 transport, and (3) diminished sand supply on ex-                Fuca Straits, Washington, to Cape Mendocino,
                                 isting beach sand buffers. Because coastal man-                 California (1,000 kilometers in distance), con-
                                 agers have not had much experience with such                    tains some 42 separate beach segments. These
                                 unusual erosional events, they generally have not               segments possibly represent proxies for indepen-
                                 considered the potential impacts of interannual                 dent littoral cells (2 to 165 kilometers long) total-
                                 redistributions of beach sands during shoreline                 ing some 770 kilometers, or about 77 percent of
                                 planning or pennitting processes.                               the coast (Peterson et al. 199 1 b). Catastrophic

                                 34







                shoreline erosion could differ between and within        swept by the tsunami wave) and inshore attenua-
                these beach segments as a function of the local          tion (landward distance reached by the tsunami).
                distribution of beach sand buffers. For example,         In addition to the uncertainty of tsunami run-up,
                measured sand volumes in selected beaches range          the lack of detailed coastal topography (land el-
                from 15 to 3,400 cubic meters per meter of shore-        evations) severely limits the prediction of site-
                line (Peterson et al. 199 1 c). As yet, no quantita-     specific tsunami hazard needed by planners and
                tive relations between pre-existing sand volume          emergency managers.
                and susceptibility to catastrophic erosion have             Of the beach-fronted PNW coastline, approxi-
                been established in the PNW coastal zone.                mately 460 kilometers (60 percent of the total)
                   Some 38 of the beach segment boundaries, that         are backed by unconsolidated dune or bay depos-
                is, about 45 percent of the cell-bounding head-          its. The remainder (40 percent of the total) are
                lands, project less than 500 meters seaward of           backed directly by sea cliffs. Unconsolidated
                adjacent shoreline embayments. Assuming 0.01             beach, dune, and bay sediments within reach of
                to 0.02 nearshore gradients (slope), these small         perched water tables are likely to be the founda-
                 Padlands can be expected to terminate in less           tion soils most susceptible to liquefaction from
                than 10 meters of water, well within reported wa-        seismic shaking. Ironically, the flat topography
                ter depths of active sand suspension and transport       and close proximity of these deposits to modem
                (U.S. Army Corps of Engineers 1973). However,            shorelines make them very appealing to private
                no field experiments have been conducted to test         and commercial developers. Although liquefiable
                the effects of these small headlands in restricting      deposits have been mapped in the Portland and
                longshore transport under highly variable condi-         Seattle metropolitan areas, they have not been
                tions of directional wave climate. For example,          regionally mapped or systematically tested for
                chronic beach erosion or dune sand accretion in          liquefaction potential anywhere in the PNW
                some cells might result from infrequent events of        coastal zone.
                sand bypassing around small headlands during                Seasonal and interannual variations in eolian
                extreme climatic events. Finally, there have been        dune sand supply are major complicating factors
                no studies of the potential long-term flux of beach      in coastal planriing for shoreline development,
                sand between inshore, offshore, or longshore             jetty maintenance, harbor mouth dredging, and
                sand reservoirs following sustained coastal sub-         dune habitat ecology. Surprisingly little informa-
                sidence (decades) associated with earthquake             tion exists regarding the site-specific rates of
                subsidence or uplift.                                    beach sand transport by eolian processes in the
                   An increasing concern of many PNW coastal             PNW coastal zone. It has been suggested that
                communities is their susceptibility to near-source       sand supplies to dune fields are alternately termi-
                tsunami hazards. In the event of a megathrust            nated and reactivated following periods of
                earthquake in the central Cascadia margin, as few        coseismic cycles of subsidence and uplift, respec-
                as 20 minutes might elapse between the tennina-          tively (Hunter, pers. comm; Carver, pers.
                tion of seismic shaking and the advance of the           comm.). Unforturiately, there have been few geo-
                corresponding tsunami (Baptista, pers. comm.).           logic studies of the origin of the major dune
                Although evidence of prehistoric tsunami inunda-         fields, their timing of formation, or their long-
                tion is now established in more than a dozen             term growth dynamics since Cooper's pioneering
                PNW bays (table 1), the geologic records do not          work (Cooper 195 8 and 1967). Finally, there
                provide accurate estimates of the heights of tsu-        have been no quantitative, site-specific studies on
                nami run-ups. Preliminary computer numeric               the long-term effects of the "locking up" of beach
                models of tsunaird generation and shoreward              sand in artificially stabilized dune fields, for ex-
                propagation have been developed for the                  ample, foreduries stabilized by dune grass
                Cascadia margin (Hebenstreit 1988; Baptista,             plantings or shore protection structures.
                pers. comm.). However, a great deal of work is              Most of the beach-fronted sea cliffs contain
                needed to refine the models for accurate predic-         poorly consolidated Pleistocene deposits overly-
                tion of tsunami onshore run-up (land elevations          ing wave-cut marine terraces, tectonically


                                                                                                                               35






                              upwarped between 0 and 120 meters above                  Acknowledgments
                              present sea level. The longshore distribution of
                              modem sea cliff failures appears to vary wide.1v            Work on natural coastal hazards performed by
                              in northern Oregon (Galster 1987; Komar and         ,    the Geology Department at Portland State Uni-
                              Shih 1991) as well as throughout the PNW. Al-            versity has been recently supported by the Na-
                              though some 90 percent of the observed sea cliffs        tional Coastal Research Institute grants no.
                              in the PNW coastal zone are oversteepened, less          2-5632-03 and CZ17.90-5635-01, the USGS Na-
                              than 10 percent of modem sea cliff shoreline             tional Earthquake Preparedness Program grants
                              (pre-1982-83 El Nifio) shows evidence of cata-           14-08-0001-GI512 and 14-08-0001-G2120, the
                              strophic slope failure (Peterson et al. 1992). In        Oregon Department of Geology and Mineral In-
                              addition, we find no regional correlations be-           dustries interagency agreements 1989-1991, and
                              tween reported modem uplift rates (Mitchell et al.       the National Science Foundation grant EAR-
                              199 1) and apparent sea cliff retreat in the             8903903.
                              Cascadia margin. We speculate that periods of
                              rapid sea cliff retreat immediately follow               References
                              coseismic subsidence events or anomalous condi-
                              tions of beach sand redistribution. The suscepti-        Atwater, B.F., 1987. Evidence for great Holocene
                              bilities of existing sea cliffs to future erosion and       earthquakes along the outer coast of Washing-
                              retreat, due either to coseismic tectonic subsid-           ton State: Science 236:942-944.
                              ence (abrupt sea-level rise) or interannual events       Cooper, W.S., 1958. Coastal sand dunes of
                              of sand redistribution by anomalous wave ch-                Oregon and Washington: Geological Society
                              mate, have yet to be evaluated in the Cascadia              of America Memoir 72, 169 p.
                              margin.                                                  Cooper, W.S., 1967. Coastal dunes of California:
                                In conclusion, the PNW coastal zone is par-               Geological Society of America Memoir 104,
                              ticularly susceptible to Cascadia margin earth-             131 p.
                              quakes from the multiple threats of (1) relative         Darienzo, M.E., and C.D. Peterson, 1990.
                              proximity to earthquake epicenters, (2) near                Episodic tectonic subsidence of late-Holocene
                              source tsunami run-up, (3) abundance of liquefi-            salt marsh sequences in Netarts Bay, Oregon,
                              able foundation soils, and (4) persistent coastal           Central Cascadia. Margin, USA. Tectonics
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                              potentially more frequent, events of unusual wave Galster, R.W., 1987. A survey of coastal engi-
                              climate make "apparently stable" shorelines in              neering geology in the Pacific Northwest:
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                              previously assumed. Finally, increasing develop-            Geologists 24:161-197.
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                              to yield increasing land-use conflicts between              assessment for the Juan de Fuca plate area.
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                              the natural dynamics of shoreline erosion or ac-            Survey, National Earthquake Hazard Reduc-
                              cretion. Coastal planners, emergency managers,              tion Program.
                              and the general public need comprehensive as-            Komar, P.D., 1986. The 1982-83 El Nifio and
                              sessments of potential, catastrophic shoreline haz-         erosion on the coast of Oregon: Shore and
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                              36







               Mitchell, C.E., R.J. Weldon, P. Vincent, and H.L.          Terich, 1992. Regional sediment dynamics and
                  Pittock, 199 1. Active uplift of the Pacific            shoreline instability in littoral cells of the
                  Northwest Margin: EOS Transactions, Ameri-              Pacific Northwest. Final Project Report to
                  can Geophysical Union 72:314.                           National Coastal Resources Research and
               Peterson, C.D., P.L. Jackson, D.J. O'Neil, C.L.            Development Institute, Newport, Oregon,
                  Rosenfeld, and A.J. Kimerling, 1990. Littoral           45 p.
                  cell response to interannual climatic forcing        Pettit, D. J., 1990. Distribution of sand within
                  1983-1987 on the central Oregon coast, USA:             selected littoral cells of the Pacific Northwest.
                  Journal of Coastal Research 6:87-110.                   Unpublished Masters Thesis, Portland State
               Peterson, C.D., M. Hansen, and D. Jones, 1991 a.           University, Portland, Oregon, p. 249.
                  Widespread evidence of paleoliquefaction in          Reinhart, M.A., and J. Bourgeois, 1989. Tsunami
                  late-Pleistocene marine terraces from the               favored over storm or seiche for sand deposit
                  Oregon and Washington margins of the                    overlying buried Holocene peat, Willapa Bay,
                  Cascadia subduction zone. EOS, Trans. Amer.             WA (abstract). EOS 70:1331
                  Geophys. Union 72:313.                               Shedlock, K.M., and C.S. Weaver, 1991. Pro-
               Peterson, C.D., M.E. Darienzo, D.J. Pettit, P.             grain for Earthquake Hazards Assessment in
                  Jackson, and C. Rosenfeld, 1991b. Littoral cell         the Pacific Northwest. USGS Circular 1067.
                  development in the convergent Cascadia               Tuttle, D.C., 1987. A small communities re-
                  margin of the Pacific Northwest, USA. In. R.            sponse to catastrophic coastal bluff erosion.
                  Osborne (ed) From Shoreline to the Abyss,               ASCE Fifth Symposium on Coastal and Ocean
                  Contributions in Marine Geology in Honor of             Management, Coastal Zone '87 2:1876-1881.
                  F.P. Shepard, SEPM Special Publication               U.S. Army Corps of Engineers, 1973. U.S. Ariny
                  46:17-34.                                               Corps of Engineers Research Center, Shore
               Peterson, C.D., D.J. Pettit, M.E. Darienzo, P.L.           Protection Manual, U.S. Government Printing
                  Jackson, C.L. Rosenfeld, and A.J. Kimerling,            Office, Washington D.C.
                  1991c. Regional beach sand volumes of the            Vick, G.S., 1988. Late Holocene paleoseismicity
                  Pacific Northwest, USA. Coastal Sediments 91            and relative sea level changes of the Mad
                  Proceedings Speciality Conference, pp. 1503-            River Slough, northern Humboldt Bay,
                  1517.                                                   Califort-tia. Masters Thesis, Humboldt State
               Peterson, C.D., M. Hansen, G. Briggs, R. Yeager,           University, Arcata California.
                  1. Saul, P.L. Jackson, C.L. Rosenfeld, and T.A.




























                                                                                                                        37







                      SCIENCE                       OCEAN PROCESSES AND HAZARDS
                                                    ALONG THE OREGON COAST

                                                    Paul D. Komar
                                                    College of Oceanography, Oregon State University, Corvallis, Oregon


              COASTAL
              PROCESSES AND                                                                                                                              The more extensive stretches of beach are
              HAZARDS                               Introduction                                                                                       found in t~qhe lower-lying parts of t~qhe coast. The
                                                    Visitors to the Oregon coast are impressed by the                                                  longest continuous beach extends from Coos Bay
                                                    tremendous variety of its scenery. The low rolling                                                 northward to Heceta Head near Florence, a total
                                                    mountains of the Coast Range serve as a back-                                                      shoreline length of some 60 miles. T~8qhis beach is
                                                    drop for most of the length of its ocean shore. In                                                 backed by the impressive Oregon Dunes, the
                                                    the south the Klamath Mountains extend to the                                                      largest complex of coastal dunes in the United
                                                    coast, and the edge of the land is characterized by                                                States. Along the northern half of the coast there
                                                    high cliffs being slowly cut away by ocean                                                         is an interplay between sandy beaches and rocky
                                                    waves. The most resistant rocks persist as sea                                                     ~sbores. Massive headlands jut out into deep wa-
                                                    stacks scattered in the offshore. Sand and gravel                                                  ter, their black volcanic rocks resisting the on-
                                                    are able to accumulate only in sheltered areas,                                                    slaught of even the largest ston~n waves. Between
                                                    where they form small pocket beaches within the                                                    these headlands are stretches of sandy shoreline
                                                    otherwise rocky landscape.


                                                                                                                                                                                                                                               ~q_~qJ
                    Figure 1: Coastal landforms of Oregon, consisting of stretches of rocky shorelines and headlands, separating pockets of sandy beaches.
                    (From Komar 1985)


                                                    38
 






               whose lengths are governed by the spacings be-           and types of problems experienced in the past can
               tween the headlands (figure 1). Portions of these        aid in the selection of a safe location for a home.
               beaches form the ocean shores of sand spits such         It can also enhance people's enjoyment of the
               as Siletz, Netarts, Nehalem, and Bayocean. Land-         coast and, it is hoped, lead to an appreciation of
               ward from the spits are bays or estuaries of rivers      the qualities of the Oregon coast that must be
               that drain the Coast Range.                              preserved.
                  The first western explorers and settlers were
               attracted to the Oregon coast by the potential           Tectonic Setting and Geornorphology
               richness of its natural resources. Earliest were the
               traders, who obtained pelts of ocean otter and              The tectonic setting of the Oregon coast is ex-
               beaver from the Indians. Later came prospectors,         tremely important to the occurrence and patterns
               who sought gold in the beach sands and coastal           of erosion. Significant is the presence of active
               mountains, but who in many cases were content            sea-floor spreading beneath the ocean to the im-
               to settle down and "mine" the fertile farm lands         mediate west. New ocean crust forms at the Juan
               found along the river margins. Others turned to          de Fuca and Gorda ridges, adding to the Juan de
               fishing, supporting themselves by harvesting the         Fuca and Gorda South plates. These oceanic
               abundant Dungeness crab, salmon, and other fish          plates, which are moving generally eastward to-
               in the coastal waters. Also important to the early       ward the continent, collide with the North Ameri-
               economy of the coast were the vast tracts of cedar       can plate, which includes the continental land
               and sitka spruce. Their significance continues to        mass. The collision zone lies along the margin of
               the present. However, today the most important           the coasts of Washington, Oregon, and northern
               "commodity" for the Northwest coastal economy            California. There is evidence that the oceanic
               is the vacation visitor: vacationers arrive by the       plates have been undergoing subduction beneath
               thousands during the summer months.                      the continental North American plate, evidence
                  It is still possible, in spite of the number of       which includes the still-active volcanoes of the
               tourists who visit the state, to leave Highway 101       Cascades, the existence of marine sedimentary
               and find the seclusion of a lonely beach or the          rocks accreted to the continent, and the occur-
               stillness of a trail through the forest. However,        rence of vertical land movements along the coast.
               there is cause for concern that the qualifies of the        Most of the marine sediments deposited on the
               Oregon coast we cherish are being lost. Like most        oceanic plates are scraped off during the subduc-
               coastal areas, Oregon is experiencing develop-           tion process and accrete to the continental plate.
               mental pressures. Homes and condominiums are             The addition of ocean sediments to the continent
               being constructed immediately behind the                 has led to the long-term westward growth of the
               beaches, within the dunes, and atop cliffs over-         Pacific Northwest. The oldest rocks found in the
               looking the ocean. Everyone wants a view of the          Coast Range date back to the Paleocene and Eo-
               waves, passing whales, and the evening sunset, as        cene periods, some 40 to 60 million years ago.
               well as easy access to a beach, but these desires        These accreted marine sediments, mainly gray
               are not always compatible with nature. As a re-          mudstones and siltstones, can be seen in many
               sult, increasingly homes are being threatened and        sea cliffs along the coast (figure 2). As will be
               sometimes lost to beach erosion and cliff land-          discussed in a later section, the presence of these
               slides. Such problems can usually be avoided if          mudstones is important to the erosion of sea cliffs
               builders recognize that the coastal zone is funda-       and particularly to the occurrence of landslides.
               mentally different from inland areas because of             In addition to the Tertiary mudstones, many
               its instability. Builders need some knowledge of         sea cliffs contain an upper layer of clean sand
               ocean waves and currents and how they shape              (figure 2). These are Pleistocene marine terrace
               beaches and attack coastal properties. In addition,      deposits and consist of uplifted beach and dune
               they need to understand and recognize potential          sands. In some areas the Pleistocene sands form
               instabilities of the land that might cause it to sud-    the entire sea cliff, with no outcrop of Tertiary
               denly slide away. A familiarity with the processes       mudstones beneath. The flat marine terrace seen


                                                                                                                              39







                                                                                                                                  t


                              Figure 2: The sea cliff at
                              Jump-OffJoe, Newport,
                              consisting of seaward-dipping
                              Tertiary mudslones and
                              uplifted Pleistocene marine
                              terrace sands.








                                                                               . ... ... ...             M
                                                                                           4
                                                                                   P
                                                                    V/'


                              in figure 2 is the lowermost and youngest terrace       land which affect the record obtained at a specific
                              of a series that in some places form a stairway up      tide-gauge site. It is known that the Galveston
                              the flank of the Coast Range. The presence of this      area is subsiding, so the 6.0 millimeters-a-year
                              stairway documents that the Oregon coast has            record from that tide gauge represents the
                              been tectoriically rising for hundreds of thou-
                              sands of years, while at the same time the sea              1900             1930                   1970
                              level has oscillated because of the growth and
                              retreat of glaciers.
                                The general uplift of the Northwest coast is                        NEW YORK, N.Y.
                              also demonstrated by records from tide gauges
                              where the hourly measurements are averaged for
                              the entire year, removing the tidal fluctuations
                              and leaving the mean sea level for that year
                              (Hicks et al. 1983). Examples of up to 80 years in                                                      20
                              length obtained by yearly averaging are shown in                                        GALVESTON,      15- -
                                                                                                                                           E
                              figure 3. Each record reveals considerable fluc-                                        TEXAS                U
                                                                                                                                      10-  Uj
                                                                                                                                           _j
                              tuations in the level of the sea from year to year,
                              with many small ups and downs. The sea level in                                                         5- CA
                              any given year is affected by many oceanic and                                                          0 _j
                              atmospheric processes. These processes cause
                              the irregular fluctuations.
                                In spite of such irregularities, most tide-gauge
                              records reveal a long-term rise in the sea that can            ASTORIA,
                                                                                              OREGON
                              be attributed in part to the melting of glaciers.
                              The record from New York City in figure 3 is
                              typical of such analyses. In that example the
                              long-term average rise is 3.0 millimeters a year,
                              about 12 inches a century (I inch = 25 millime-                                 JUNEAU,
                              ters). The record from Galveston, Texas, also                                     ALASKA
                              shows a rise, but the average rate is much higher
                              at 6.0 millimeters a year (24 inches a century).
                              The actual level of the sea cannot be going up
                              faster at Galveston than at New York CitY-the           Figure 3: Yearly changes in sea level determinedftom tide
                              discrepancy results from changing levels of the         gauges al various coastal stations. (After Hicks [1972])

                              40







                 combined effects of the local land subsidence and             than absolute, so the elevation changes have been
                 the actual rise in sea level. An extreme case of              normalized to the bench mark in Crescent City.
                 this is Juneau, Alaska, figure 3, which is tectoni-           Accordingly, the elevation change scale on the
                 cally rising at a rate that is faster than the rise in        left of the diagram gives 0 for Crescent City,
                 sea level. Its tide-gauge record, therefore, indi-            while positive values for other locations represent
                 cates a net fall in the water level relative to the           an increase in elevation relative to Crescent City
                 land.                                                         and negative values indicate reduced elevation
                    The record from the tide gauge at Astoria, Or-             relative to Crescent City. (However, the elevation
                 egon, is included in figure 3-the level of the sea            could still involve tectonic uplift.) The overall
                 there has remained relatively constant with re-               pattern seen in figure 4 indicates that the smallest
                 spect to the land. This must indicate that during at          uplift has occurred along the north-central coast
                 least the last half century, Astoria has been rising          between Newport and Tillamook, with progres-
                 at just about the same rate as the sea. A detailed            sively higher uplift ftirther south and along the
                 analysis of the measurements from the Astoria                 very northernmost portion of the coast toward
                 gauge indicates that the land is actually rising              Astoria and the Columbia River. The first scale
                 slightly faster than the water, the net increase in           on the right of figure 4 indicates the equivalent
                 the land relative to the sea being 0. 1 to 0.2 milli-         rates, calculated as the elevation changes divided
                 meters a year. This change is small, amounting to             by the lapsed time between the surveys (1988-
                 a 10- to 20-millimeter (less than an inch) increase           1931 = 57 years). The differential rates are sig-
                 in land elevation if it continued for 100 years.              nificant; for example, they amount to 2 to 3
                 The land must be rising at a faster rate at Neah              millimeters a year when we compare Astoria and
                 Bay on the north coast of Washington, where the               the south coast with the Newport and Lincoln
                 net rate is 1.3 millimeters a year (5 inches a cen-           City areas. It is possible to use the tide-gauge data
                 tury) in excess of the global sea-level rise, and at          to convert the elevation changes relative to Cres-
                 Crescent City in northern Califon-da, with 0.7                cent City determined by Vincent (1989) into rates
                 millimeter a year, or 2.8 inches a century, of net            relative to the annual change in the global level of
                 land emergence (Hicks et al. 1983).                           the sea. This is done simply by shifting the first
                    Data from geodetic surveys collected by the                scale on the right of figure 4, that relative to the
                 National Geodetic Survey permit us to infer the               Crescent City bench mark, by an amount 0.7 mil-
                 movement of the land relative to the sea along the            limeter a year determined from the tide gauge at
                 remainder of the Oregon coast. Vincent (1989)                 that location. This shift yields the rate scale far-
                 and Mtchell et al. (199 1) have analyzed the geo-             thest to the right in figure 4, the rate of land-level
                 defic data along a north-south line extending the             change relative to the changing global sea level.
                 full length of the Oregon coast. To establish el-             A positive value again indicates that the elevation
                 evation changes, they compared surveys made in                of the land is increasing relative to the sea, while
                 1931 and 1988; the values are graphed in figure               a negative value corresponds to inundation of the
                 4. The movement so determined is relative rather              land by the rising sea. This coast-wide shift of the


                      200                                                                                                                       Figure 4:
                                                                                                                            3  >'               Elevation changes
                                                                                                                                          W     and their
                                                                                                                                          3
                                                                                                                                          >
                 E     100-                 Co                 C13                   0                  0                                 W     relationship to sea-
                                                                                     CL                 E
                                                               10                                                              Z          2     level rise along the
                                                               0                                                               W
                                                          co   0
                 W.                                                                 Z       _J                                                  length of the
                 L
                    1-   0-                                                                                                 0             W
                 L                                                                                                                        U)    Oregon coastfrom
                 3                                                                                                             W
                                           --------------                   ------------------------                           M          00    Crescent City in
                 Z                                                                                                                        Z     California north to
                 0  CD _100-                                                                                                   0 --1      E
                    CD                                                                                                   -2    1---             Astoria on the
                                                                                                                                          wE
                                                                                                                                   -2     Cr    Colunibia River,
                 >                                                                                                             _J
                 W                                                                                                       -3    W          W     based on repeated
                 _J  -200           data from Vincent (1989)                                                                   Cr
                 W                                                                                                       -4    W          3<    geodetic surveys
                                                                                                                               F-         Cr    along the coast.
                                                                                                                           -5  X          4
                     -300                                                                                                -     a:               (After Vincent
                                   42                  43                   44                45                 46                             [19891)
                                                             LATITUDE

                                                                                                                                          41







                              scale by 0.7 millimeters a year, based on the tide       subduction. However, recent evidence suggests
                              gauge at Crescent City, indicates that Astoria at        that the plates are temporarily locked together and
                              the far north is rising faster than the sea by an        that the 200-year historical record from the
                              amount on the order of 0. 1 to 0.2 millimeter a          Northwest is too short to establish whether earth-
                              year, the same measurement recorded by the tide          quakes do accompany subduction. This evidence
                              gauge at that location. These matching data con-         has come from investigations of estuarine marsh
                              firm (1) the validity of the geodetic data analyzed      sediments buried by sand layers, deposits which
                              by Vincent to determine elevation changes and            suggest that during prehistoric times portions of
                              (2) the analyses undertaken to convert that data         the coast have abruptly subsided, generating an
                              into a rate of change that can be compared with          extreme tsunami that swept over the area to de-
                              the increasing level of the sea.                         posit the sand (Atwater 1987; Atwater and
                                 According to the results graphed in figure 4,         Yamaguchi 1991; Darienzo and Peterson 1990).
                              the southern half of the Oregon coast is currently       Based on the number of such layers found in
                              rising faster than the global sea level, as is the far   Willapa Bay, Washington, and Netarts Bay, Or-
                              north coast near Astoria. Conversely, the central        egon, it has been estimated that catastrophic
                              stretch between Newport and Tillamook is being           earthquakes have occurred at least six times in the
                              submerged by the rising sea. The latter rates are        past 4,000 years, at intervals ranging from 300 to
                              on the order of 1 to 2 millimeters a year (4 to 8        1,000 years. The last- recorded event took place
                              inches a century), and therefore are small com-          about 300 years ago. Therefore, there is strong
                              pared with submergence rates experienced on              evidence that major subduction earthquakes do
                              most coastlines: rates of 4 to 6 millimeters a year      occur along the Northwest coast, but with long
                              (16 to 24 inches a century) are common along the         periods of inactivity between events.
                              east and Gulf coasts of the United States (figure           An earthquake releases strain built up by sub-
                              3). 'Me global rise in sea level has been estimated      duction. This results in some areas of the coast
                              by various workers to be on the order of I to 3          dropping by I to 2 meters (3 to 6 feet) during the
                              millimeters a year (4 to 12 inches a century), the       release, while other areas undergo minimal sub-
                              large range being due to the difficulty of separat-      sidence. Between earthquake events the strain
                              ing that worldwide component from local tec-             accumulates; this produces a general uplift of the
                              tonic and isostatic effects included in records          coast as recorded by the tide gauges and geodetic
                              from tide gauges. Assuming that the eustatic rise        surveys within historic times (figures 3 and 4).
                              in sea level is on the order of 2 millimeters a year        Another potential change in the present-day
                              (8 inches a century), the results from figure 4 in-      pattern of sea-level rise versus coastal uplift is
                              dicate that the south coast of Oregon is tectord-        associated with predictions that future greenhouse
                              cally rising at about 2 to 3 millimeters a year (8 to    warming will accelerate the rise in sea level.
                              12 inches a century) whereas the stretch between         Some scientists have predicted that global tem-
                              Newport and Tillamook is approximately stable,           peratures will increase from 1.5' to 4.5' by the
                              neither rising nor failing tectonically.                 year 2050 (National Research Council 1983).
                                 It is apparent that the along-coast differences       These predictions in turn have led to a variety of
                              between tectonic uplift and changing levels of the       estimates for accelerated sea-level rise caused by
                              sea deduced from figure 4 will be relevant to spa-       increased glacial melting and thermal expansion
                              tial patterns of coastal erosion. However, there         of seawater. For example, a report by the Na-
                              also appears to be a temporal change in the tec-         tional Research Council (1987) predicts that by
                              tonics that is important to erosion. Earthquake          the year 2025, the global sea level will have risen
                              activity is generally associated with a subduction       10 to 21 centimeters (4 to 8 inches). Although
                              zone such as that in the Northwest, where seismic        this may seem insignificant, the effects on sandy
                              events are triggered by the plates scraping to-          shorelines may be magnified 100 times in the
                              gether as the oceanic plate slides beneath the con-      horizontal direction, resulting in shoreline erosion
                              tinental plate. The Northwest coast is anomalous         of 10 to 21 meters (33 to 70 feet). There are many
                              in that respect in that there have been no historic      uncertainties in these analyses of sea-level rise
                              earthquakes which can be attributed to plate             caused by greenhouse warming, and the resulting

                              42







               predictions have been controversial among scien-        winds. The importance of fetch is apparent when
               tists. Different investigators studying sea-level       one contrasts wave generation on the ocean with
               curves derived from tide gauges have reached            that on an inland lake. The fetch on the lake can
               conflicting results, some concluding that they see      be no greater than its length, so the waves can
               an increase in the rate of rise in recent decades       acquire only a small amount of energy from
               and others concluding that they do not. Despite         winds before they cross the entire lake and break
               the uncertainties, there is a growing consensus         on the shore.
               that some increased rate of sea-level rise can be          Wind-generated waves are important as en-
               expected in the next century. This recognition has      ergy-transfer agents. They obtain their energy
               led to reconunendations that future sea levels be       from the winds, transfer it across the expanse of
               given more serious consideration in coastal man-        the ocean, and finally deliver it to the coastal zone
               agement decisions.                                      when they break on the shoreline. Therefore, the
                                                                       storm need not be in the immediate coastal zone.
               Ocean Processes as Agents of Erosion                    Waves reach the shores of Oregon from storms
                                                                       all over the Pacific, even from the southern hemi-
                  The Northwest coast is one of the most dy-           sphere near Antarctica. However, the largest
               namic environments in the world. Ocean waves            waves reaching Oregon derive from winter storm
               and currents continuously reshape the shoreline.        systems that move down from the north Pacific
               Portions of the beach are cut away while others         and Gulf of Alaska.
               are built out. Severe storms strike the coast during       Ocean waves reaching the shores of Oregon
               the winter, generating strong winds that drive rain     are measured daily by a unique system, a
               against sea cliffs and homes and form huge ocean        microseismometer like those usually employed to
               waves that crash against the shore. Beaches, giv-       measure small earth tremors. In this application
               ing way to waves and currents, retreat toward the       the microseismometer senses ground movements
               land. At times this beach loss continues until the      produced by ocean waves as they reach the shore
               erosion threatens structures and cuts away at pub-      and break. Many Coast Guard stations in the
               lic parklands.                                          Northwest now use this system to obtain better
               Ocean Waves                                             estimates of wave conditions than were formerly
                  The extreme seasonality of the Oregon climate        determined visually. A microseismometer system
               results in parallel variations in ocean processes       is also in operation at OSU Hatfield Marine Sci-
               that exert the primary control on natural cycles        ence Center in Newport; it is connected to a re-
               observed on beaches. 'Me energy of ocean waves          corder to obtain a permanent record of the waves.
               parallels the seasonality of storm winds because        This system has been in operation since Novem-
               the strength of those winds is the primary factor       ber 1971 and has yielded the longest continuous
               in causing the growth of waves. In general, the         record of wave conditions on the west coast of
               greater the wind velocity blowing over the sur-         the United States. These measurements have been
               face of the ocean, the higher the resulting waves.      valuable in research examining the causes of
               Other factors are involved in addition to the wind      beach erosion along the Oregon coast.
               speed. One is the dur-ation of the storm-the               It might come as a surprise that a microseis-
               longer the winds blow, the more energy they are         mometer at the Marine Science Center can
               able to transfer to the waves. The third factor is      provide records of ocean waves-after all, the
               the fetch, the area or ocean expanse over which         center is nearly two miles from the ocean.
               the storm winds are effective. Fetch operates           However, even more impressive is that the waves
               much like storm duration in that the area of the        can be detected on the seismometer at Oregon
               storm governs the length of time the winds are          State University in Corvallis, 60 miles inland.
               able to act directly on the waves. As the waves         Whenthe surf is high on the coast, its effects can
               are forming they move across the ocean surface          be seen as small jiggles in the seismometer
               and may eventually pass beyond the area of the          recordings.
               storm so they no longer acquire energy from the            The microseismometer at the Marine Science
                                                                       Center differs from normal seismometers in that


                                                                                                                            43







                              it is tuned to amplify small tremors, whether they         the microseismometer are directly proportional to
                              are caused by earthquakes too minor to be felt or          the heights of the offshore waves. Now only the
                              by ocean waves along the coast. To use the                 microseismometer is needed to monitor daily
                              record from the microseismometer to measure                ocean-wave conditions.
                              ocean waves, it was necessary to first calibrate              An example of daily wave measurements ob-
                              the system (Creech 1981; Zopf et a]. 1976). This           tained from the microseismometer is shown in
                              was accomplished by obtaining direct measure-              figure 5, covering the period from mid-December
                              ments of waves in the ocean at the same time               1972 to mid-January 1973. Most apparent in this
                              their tremors were measured with the microseis-            series are the stonn waves that struck the coast
                              mometer. The direct measurements of waves                  during Cliristmas. The breaker heights at that
                              were collected with a pressure transducer, an in-          time reached 7 meters, about 23 feet, roughly the
                              strument that rests on the ocean bottom and                height of a three-story building. This reported
                              records pressures that are directly proportional to        height represents what is termed a "significant
                              the heights of the waves passing over the trans-           wave height," defined as the average of the high-
                              ducer. This is the most common method for di-              est one-third of the waves. The significant wave
                              rectly measuring ocean waves, and it would be              height can be evaluated from measurements of
                              preferable to use such an instrument rather than a         the waves obtained using wave-sensing instru-
                              microseismometer. However, winter storms                   ments. However, it turns out that the significant
                              experienced along the Northwest coast are so               wave height also roughly corresponds to a visual
                              intense they usually destroy pressure transducers          estimate of a representative wave height. This is
                              or other wave-measuring instruments that must              because observers normally tend to weight their
                              be placed in the water. On this coast we need a            observations toward the larger waves, ignoring
                              microseismometer that can remain at the Marine             the smallest. There will of course be many indi-
                              Science Center, safe from the reach of waves.              vidual waves that are still higher than Us re-
                              Although the direct comparisons between the                ported significant wave height, which remains
                              pressure-transducer records and those obtained             something of an average. Measurements have
                              with the microseismometer lasted only a few                shown that the largest wave height during any 20-
                              months, the results showed that the motions on             minute interval will be a factor of about 1.8 times


                                                                      15      20     25       31 1     5      to      15     20       25         31
                                                            Ld    3.5 -11


                                                                  3.0-

                                                                E


                                                                  2.5-
                                                            W   W,
                                                            Cn
                              Figure 5: An example of       cc
                              daily variations in wave      0     2.0
                              conditions measured by the              15      20     25       31 1     5      10      15     20      25          31
                                                                      11 1111111111111                                                 FTTTT-T-F
                              microseismomeler at                   7
                              Newport, covering the
                              infervalfrom December
                              1972 through January              t
                              1973. (From McKinney              9
                              [19771)                               5 -


                                                                W   4 -
                                                                X:
                                                                cr
                                                                W
                                                                    3
                                                                W


                                                                    2
                                                                                                                             rTTTTTTTFTT


























                                                                     F






                                                                      15      20     25       311      5      10      15     20      25          31
                                                                          DECEMBER 1972                             JANUARY 1973




                              44







                    the significant wave height (Komar 1976). There-                 1972-73 period (the storm waves that are shown
                    fore, when the graph of figure 5 indicates the oc-               on a daily basis in figure 5) reached the coast dur-
                    currence of a significant wave height of 23 feet                 ing the final third of December 1972.
                    during Cliristmas 1972, there must have been in-                     Although extremely high, the waves during
                    dividual waves of about 1.8 x 23 feet-41 feet                    that December 1972 storm are well below the
                    high! As might be expected, there was consider-                  largest that have been measured off the North-
                    able erosion along the coast during that storm, the              west coast. In the early 1960s, a wave-monitoring
                    severest impact having been at Siletz Spit on the                program on offshore rigs exploring for oil mea-
                    mid-Oregon coast.                                                sured an individual wave having a height of 95
                       Figure 6 gives an example of annual changes                   feet (Rogers 1966; Watts and Faulkiier 1968).
                    in wave-breaker heights measured by the                          This is close to the I 12-foot height of the largest
                    microseismometer. The measurements were ob-                      wave ever reliably measured in the ocean. It was
                    tained from July 1972 through June 1973 but are                  observed from a naval tanker traveling from Ma-
                    typical of annual variations (Komar et a]. 1976a).               nila to San Diego in 1933 (Komar 1976). All of
                    These data again represent significant wave                      the measurements on the Oregon coast confirin
                    heights. The solid line gives the average of the                 that it has one of the highest wave-energy cli-
                    significant breaker heights measured during each                 mates in the world.
                    one-third month interval. It shows that the break-               Beach Cycles on the Oregon Coast
                    ers are on the order of 2 meters high (7 feet) dur-                 Beaches respond directly to the seasonal
                    ing the summer months and nearly double to                       changes in wave conditions. The resulting cycle
                    about 4 meters (13 feet) in the winter. The dashed               (illustrated schematically in figure 7) is similar on
                    lines are the maximum and minimum wave                           most coastlines. The beach is cut back during the
                    breaker heights that occurred during those one-                  winter months of high waves when sand is eroded
                    third month intervals; these extremes provide a                  from the shallow underwater and from the beach
                    better impression of the effects of individual win-
                                                                                     berm (the nearly horizontal part of the beach
                    ter storms. The largest waves recorded within this


                       13      1        1       1       1       1        1        1     1       1       1       1
                       12 - WAVE PERIOD

                       11

                       10 -
                                                                                                                             Figure 6: The
                       9 -
                    W                                                                                                        monthly variations of
                       8 -
                    Al                                                                                                       wave breaker heights
                       7  JULY    AUG     SEPT    OCT     NOV     DEC       JAN.   FEB.    MAR.    APR,    MAY     JUNE      and periods at
                                                                                                                             Newport, illustrating
                                                                                                                             the occurrence of
                       7                                                                                                     higher wave
                           BREAKER HEIGHTS                                                                                   conditions during the
                       6                                      fit                                                            winter months. The
                                                                                                                             solid line isfor the
                                                                                              'AI
                                                                                                                             mean heights
                       5                                                                                                     (significant wave
                    2                                           to                                                           heights)jor one-third
                                                                                                                             month intervals, and
                                                                11
                    1  4                                                                                                     the dashed lines are
                                                                                                                             for the largest and
                                                                                                                             smallest breakersfor
                    X  3                                                                    A
                                                                                                                  't if      those intervals.
                                                                                                                             (From Komar et al.
                    S  2                                                 @'l                                                 [1976a])



                       01 JULY    AUG,    SEPT.  19i72 OCT 1 NOV.  DEC.  i  JAN,   FEB,    MAR. 1973 APR.   MAY     JUNE

                                                                                                                                                     45













                               Figure 7: The
                               general pattern of                                       swell (summer) profile
                               seasonal changes in                                 swell profile shoreline                           line     Sea
                               beach profiles                                                                                                 Cliff
                               associated with               mean water level
                               parallel variations
                               in wave energies.
                                                                                              or
                               (From Komar                                        trough
                               [19761)                                 bar
                                                                                                  storm (winter)    profile







                               profile which is above the high-tide line). This             winter of 1976-77 from two beaches, that to the
                               eroded sand moves to deeper water where it                   south of Devil's Punchbowl at Otter Rock and
                               accumulates in offshore bars, approximately the              that at Gleneden Beach south of Lincoln City
                               zone where the waves first break as they reach               (Aguilar and Komar 1978). These two beaches
                               the coast. Sand movements reverse during the                 were selected because of their contrasting sand
                               summer months of low waves, moving back                      sizes, which produce marked differences in over-
                               onshore from the bars to accumulate in the berm.             all slopes of the profiles. The sediment grain size
                               Although this cycle between two beach-profile                is the primary factor that governs the slope of a
                               types is approximately seasonal due to changing              beach, the slope increasing with increasing grain
                               ocean waves, the response is really one to high              size. Gravel beaches are the steepest, their slopes
                               storm waves versus low regular swell waves. At               sometimes reaching 25 to 30 degrees, whereas
                               times, low waves can prevail during the winter               the overall slope of a fine-sand beach may be
                               and the beach berm may actually build out,                   only I to 2 degrees. This is seen in the compari-
                               although not generally to the extent of the                  son of beach profiles of Otter Rock and Gleneden
                               summer berm. Similarly, should a storm occur                 Beach, figure 8, the latter being coarser and hence
                               during the summer, the beach erodes.                         steeper.
                                  This cycle has been demonstrated to occur on                 The month-by-month changes in the profiles at
                               Oregon beaches, just as along other coasts. In one           Gleneden Beach are shown in figure 9. These
                               study, profiles were obtained monthly during the             profiles were obtained by using standard



                                                                                                               Both Profiles 2 April 1977
      Figure 8: Beach          -                   GLENEDEN BEACH                                              IOX Vertical Exaggeration
      proftlesfrom             -                    median grain size - 0. 35 mm
      Gleneden Beach
      and Devil's
      Punchbowl Beach          -
      (Otter Rock),                                            high - tide level
      Oregon, illustrating                                                                             DEVIL'S PUNCHBOWL BEACH
      that the coarser-                                                                                median grain size - 0. 23 mm
      sand beach
      (Gleneden) is               I meter
      sleeper. (From
      Aguilar and Komar                                                                                                            low- tide level
      119781)


                                                                                                      L     I     _L    I
                               0         20          40          60          80           100        121          140         1          180         200
                                                                                 DISTANCE IN METERS



                               46








                                     surveying gear and by wading into the water.                                                           is also much faster for the coarser-grained beach:
                                     They do not show the offshore bars that were too                                                       die storm waves not only cut back the coarser
                                     deep to reach. However, these profiles do illus-                                                       beach to a greater degree but also erode it at a
                                     trate the rapid retreat of the beach as the winter                                                     much faster rate. Here nature goes counter to
                                     season develops. The erosion began as early as                                                         what might intuitively have been expected.
                                     October and continued through the spring. The                                                               This greater response of coarser-grained
                                     return of sand to the berm and the buildup of the                                                      beaches to storm waves is important to coastal-
                                     beach did not take place until April through June.                                                     erosion processes since the waves are able to cut
                                     The cycle of profiles at the Otter Rock beach was                                                      rapidly through the beach to reach homes and
                                     basically the same, at least in its timing. How-                                                       other structures. This fact points to the general
                                     ever, the magnitude of the change was much                                                             role of the beach as a buffer between the ocean
                                     smaller than at Gleneden Beach. Sand elevations                                                        waves and coastal properties. During the summer
                                     at Gleneden changed by as much as 2 to 3 meters                                                        when the beach berin is wide, the waves cannot
                                     (8 feet) (figure 9), while the changes at Otter                                                        reach the properties. Erosion is not a problem,
                                     Rock amounted to less than I meter (3 feet). This                                                       thanks to the buffer protection offered by the
                                     difference again can be attributed to differences                                                      beach. However, when the beach is cut back dur-
                                     in grain sizes between these two beaches. In gen-                                                      ing the fall and early winter, it progressively loses
                                     eral, the coarser the grain size of the beach sand,                                                    its buffering ability and property erosion is more
                                     the larger the changes in its profile in response to                                                   likely. If a storm strikes the coast in October,
                                     varying wave conditions. The response to storms                                                        there may be enough beach to serve as a buffer so

Figure 9: A series of 
beach profiles
obtained at Gleneden
Beach, Oregon,
illustrating the
seasonal variations
for Oregon coast
veaches as shown
schematically in 
figure 7, (Front
Aguilar and komar
[1978])

47
 






                               that property erosion does not occur. It is only               a rip current is approached. Rip currents can be
                               when the beach berm completely disappears and                  very strong, cutting through the offshore bars to
                               the waves can wash against cliffs and foredunes                produce deeper water and a steeper but more
                               that the potential for property losses is great. This          uniform beach slope. The rips move sand off-
                               is often the condition from about November                     shore and thereby tend to erode crescent-shaped
                               through March, but in fact the extent of the rem-              embayments into the beach berm. Aerial views of
                               nant berm is extremely variable along the coast,               the coast typically show beaches that are
                               as is the parallel threat of property erosion. This            extremely irregular, consisting of a series of rip
                               longshore variability results from the patterns of             embayments of various sizes together with
                               nearshore currents which assist the waves in cut-              troughs cut by the longshore currents and rip
                               ting back the beach.                                           currents (figure 11). At times these rip-current
                               Nearshore Currents and Sediment Transport                      embayments extend across the entire width of the
                                  Waves reaching the coast generate cumnts 'in                beach and begin to cut into foredunes and sea
                               the nearshore zone that are important to sand                  cliffs. Such rip embayments have played a major
                                                                                              role in property losses due to erosion. Although
                               movements on the beach and thus to erosion pro-
                               cesses. These wave-generated currents are inde-                rip e .mbayments seldom produce much property
                               pendent of ocean currents that exist farther                   erosion on their own, they have the effect of
                               offshore since those deep-ocean flows do not                   eliminating the buffer protection of the beach
                               extend into the very shallow waters of the                     berm. When a storm occurs, the waves are able to
                                                                                              pass through the deep water of the rip embay-
                               nearshore.
                                  Most of the time waves along the Oregon coast               ment, not breaking until they reach the properties.
                               approach the beaches with their crests nearly par-             Thus, rip embayments can control the center of
                               allel to the shoreline. Under such circumstances               attack by stonn waves. The resulting erosion is
                               the nearshore currents take the form of a cell                 commonly limited in longshore extent to only one
                               circulation, the most prominent part of which is               or two hundred yards; this is the longshore span
                               the seaward-flowing rip currents (figure 10). The              of a rip embayment that maches the foredunes or
                                                                                              sea cliff (figure 12).
                                                                                                                                When waves break at
                                                                                                                            an angle to the beach,
       Figure 10: The                                                                               RIP                     they generate a current
       nearshore cell                                                                               HEAD                    that primarily flows par-
       circulation                                                                                                          allel to the shoreline.
       consisting of                                                                                                        However, even then sea-
       seaward-flowing rip                                        RErURN FLOW
       currenis and                                               4       4                                                 ward-flowing rips may
       longshore currents                                                                                                   be present. This long-
       whichfeed water to                                                           E
       the rips.                                                -BREAKER ZON                                                Shore Current, together
                                                                                                                            with the waves, pro-
                                                              LONGSHORE cu1?1?EN.rs
                                                                                                                            duces a transport of sand
                                                                                               CUS
                                                                                                                            along the beach, a sand
                                                                                                                            movement that is known
                                                                                                                            as "littoral drift." This is
                                                                                                                            more than a local
                                                                                              rearrangement of the beach sand with accom-
                               rip currents are fed by longshore currents flowing             panying topographical changes as produced by
                               roughly parallel to shore, but extending along
                               only a short stretch of beach. The currents of this            rip currents and the cell circulation. Instead, the
                               cell circulation are able to move sediments and                littoral drift may involve along-coast movements
                               thus to affect the morphology of the beach. The                that displace sand by many miles.
                               longshore currents hollow out troughs into the                    On Oregon beaches the waves tend to arrive
                               beach, generally increasing in width and depth as              from the southwest during the winter and from

                               48







                  the northwest during the sum-
                                                                                         0
                  mer (corresponding to
                  changes in wind directions).
                                                                                                ZM
                  As a result, there is a seasonal
                                                                                 k
                  reversal in the direction of                                                                                               Figure 11: The beai
                                                                                                                                             along Nestucca Spit
                                                                       "Wow
                  littoral drift-north in the                                                                                                photographed durir
                                                                                                                                             low tide, showing d
                  winter, south during the sum-                      @7                                                                      troughs and
                                                                        fk_-
                  mer. The net littoral drift is
                                                                                                                                             embaymenis erode6
                  the difference between these                                                                                               by longshore
                                                                                                                                              urrents and rip
                  north and southward sand
                  movements. Along most of                                                                                                   currents.
                  the Oregon coast this net drift
                  is essentially zero, at least if
                  averaged over a number of
                  years. This is demonstrated by
                  the absence of continuous accumulations of sand               the north, but this was due to the oblique orienta-
                  on one side of jetties or rocky headlands, with               tion of the jetties to the overall trend of the coast-
                                                                                line and because the prejetty shoreline curved
                       OCEAN                                                    significantly inward toward the bay. More sig-
                                                                                nificant is that sand accumulated both north and
                                                                                south of the jetties until the embayments between
                                                                                the jetties and the prejetty shoreline filled and an
                                                          breaking waves        equilibrium shoreline developed. Subsequent to
                                                                                achieving equilibiium, there has been almost no
                                                              beach edge        change in the shoreline configuration. The sand
                                                              dune edge         that accumulated adjacent to the jetties derived
                                                                                from erosion of the beaches more distant from
                       1:1 El El El El El El                 El El              the etties, and so an overall symmetrical pattern
                                           I I I                                   i
                        SPIT             endangered                             emerged, one that is significantly different from
                                           homes                                the asymmetrical pattern found on coasts where
                  Figure 12: A schematic diagram illustrating how rip           there is a large net littoral drift (compare figure
                  currents erode embayments that can cut through the beach
                  and locally threaten properties.                              13A with figure 13B). This reduces the potential
                  erosion on what would be the downdrift side                   for major erosional and property losses due to the
                  (Komar et a]. 1976b). Patterns of sand accumula-              construction of jetties on the Oregon coast, at
                  tion and erosion on opposite sides of jetties, fig-           least compared with other coasts where there is a
                  ure 13A, are found on many coasts where there is              large net littoral drift. However, one severe ero-
                  a net littoral drift. For example, along the shores           sion problem did occur on the Oregon coast in
                                                                                direct response to jetty construction, that which
                  of southern California and most of the east coast             led to the destruction of the town of Bayocean
                  of the United States, erosion in the downdrift di-            (discussed below).
                  rections from jetties has caused major problems
                  and considerable loss of property (Komar 1976,                The Pocket-Beach Nature of the Oregon
                  198 3b). In contrast, when jetties have been built            Coast and Sources of Nearshore Sands
                  on the Oregon coast, sand has accumulated on                     The ultimate cause of the zero net littoral drift
                  both their north and south sides. This pattern is             of sand along the Oregon coast is that the
                  diagramed schematically in figure 13B and is il-              beaches are contained between rocky headlands,
                                                                                in effect forming pocket beaches (figure 1). The
                                                              bea ';"
                                                              d e edge



















                  lustrated specifically by the Yaquina Bay jetties             headlands are lar e and extend to sufficiently
                  in figure 14. In the case of the Yaquina Bay jet-                                9
                  ties, more sand accumulated to the south than to              deep water to prevent beach sand from passing
                                                                                around them. Therefore, the sand within each


                                                                                                                                         49







                                    A. NET LITTORAL                DRIFT                                 south closest to the Columbia River, decreasing
                                                                                                         to the north until beyond Copalis Head where net
                                                           (D @CE 11 N                                   erosion prevails.
                                                                                      net littorol           On many coastlines sand spits grow in the
         Figure 13: The                                                                                  direction of the net littoral drift. The Long Beach
         patterns of sand                                                      deposition wo,  C"'t      peninsula extends northward from the Columbia
         accitunulation
         aroundjetties,                                                                                  River and likely reflects the net sand movement
         contrasting the                              erosiion                                           along the Washington coast. It is unclear whether
         condition where the
         jetties block a net                                                                             this northward growth has continued within
         littoral drift and the                                                                          historic times since there have been many cycles
         case where there is                                                                             of growth and erosion at the tip of the peninsula.
         not a net littoral
         drift. Thejetties on      B. ZERO NET DRIFT                                                     There are a number of sand spits along the
         the Oregon coast                                                                                northern coast of Oregon, some pointing north
         correspond to the
         latter condition.                           OCEAN                                               and others pointing to the south (figure 1). Those
                                                                                  wave crests            spits are located within the beach cells where
                                                                                                         zero net littoral drift prevails, and their directions
                                                                                                         do not provide testimony as to net longshore
                                                                                                         sand movements.
                                             erosion                                     erosion
                                                      de sition               deposition                    Given the pocket-beach nature of the Oregon
                                                                                                         coast, the question arises as to the sources of
                                                                                                         beach sand contained within those littoral cells.
                                                                                                         These sources are reflected in the small quantities
                                  pocket beach is isolated. Sand may move north                          of heavy minerals contained within the beach
                                  and south within a pocket because of the season-                       sand. On the Oregon coast the beach sand gener-
                                  ality of the wind and wave directions, but the                         ally consists of grains of quartz and feldspar min-
                                  long-term net movement must be zero. Each of                           erals. Those particles are transparent or a light
                                  these pocket beaches on the Oregon coast can be                        tan, and this is what governs the color of most
                                  thought of as a littoral cell. This is a useful con-                   beaches. However, the sands also contain small
                                  cept in considering sources and loss of sediments                      fractions of heavy minerals that are black, pink,
                                  on the beach, the so-called budget of littoral sedi-                   various shades of green and other colors. These
                                  ments. As will be discussed later, the patterns and                    grains are readily apparent as specks in a handful
                                  magiiitudes of erosion differ even from cell to                        of beach sand and are sometimes concentrated by
                                  cell, particularly the erosion of sea cliffs.                          the waves into black-sand placer deposits on the
                                     The one beach on the Oregon coast that does                         beaches. Of importance is that these heavy miner-
                                  not fit this pattern of a zero-drift pocket and self-                  als are indicative of the rocks they came from. As
                                  contained littoral cell is the shoreline that extends                  a result, in many cases they can be traced to spe-
                                  south from the Columbia River, past Seaside to                         cific rocks and therefore to geographical sources.
                                  Tillamook Head. This is the Clatsop Plains,                            That is the case for the heavy minerals in the
                                  fortned by the accumulation of Columbia River                          sands of the Oregon coast. Most distinctive are
                                  sand, part of which moves southward until it is                        the heavy minerals derived from the Klamath
                                  blocked by Tillamook Head. The bulk of sand                            Mountains of southern Oregon and northern Cali-
                                  derived from the Columbia River moves                                  forriia, eroded from a great variety of ancient
                                  northward along the coast of Washington. The                           metamorphosed rocks. As diagramed in figure
                                  quantity of this northward sand transport can be                       15, sands derived from the Klarnaths contain
                                  only roughly estimated, but the primary evidence                       minerals such as glaucophane, staurolite, epidote,
                                  for this sand supply is that many of the beaches                       zircon, homblende, hypersthene, and the distinc-
                                             emsl@.
                                                      deposition









































                                  along the southern half of the Washington coast                        tive pink garnet which in particular can often be
                                  are growing (Phipps and Smith 1978). The                               seen concentrated on the beach. In contrast, the
                                  highest rates of beach growth tend to be in the                        rivers that drain the Coast Range transport sand


                                  50






                   that contains almost exclusively two                      ENTRANCE TO
                   minerals, dark-green augite and a                    YAQUINA BAY, OREGON
                   small amount of brown homblende
                                                                        High tide shoreline advance due to
                   (figure 15). Augite comes from vol-                  jetty construction. Based on Corps        NEWPORT
                   canic rocks and is washed into the                   of Engineers surveys and recent
                   rivers by erosion of the ancient sea-                aerial photographs.
                   floor rocks uplifted into the Coast
                                                                                                                                       YAQUINA              Figure 14:
                   Range. The Colurribia River drains a                                                                                   BAY               Compilation of
                   vast area that contains many types of                                                                                                    shorelines at the
                                                                                                                                                            Yaquina Bay jetties,
                   rocks. This is reflected in the diver-                                                                                                   the 1830 shoreline
                   sity of the heavy minerals in its sand                                                                                                   representing the
                   (figure 15).                                                                                                                             prejetty configur-
                                                                                                                                                            ation. Sand
                      The presence of sand derived from                                                                                                     accumulated both to
                   the Klamath Mountains in beaches                                                                                                         the north and south,
                                                                                                                                                            but the volume to the
                   along almost the entire length of the                                                                                                    south is greater
                   Oregon coast is initially surprising in                                                                            -N-                   becausethe
                   view of the many headlands that pre-                                                     2                                               embayment created
                                                                                                            2!                                              between the con-
                   vent any longshore sand transport for                                                                                                    structedietty and the
                   that distance. However, thousands of                                                                          0           500            prejetty shoreline
                   years ago during the maximum devel-                                                                                meters                was larger, and
                                                                                                                                                            becausethe
                   opment of glaciers, the sea level was                                                                                                    orientation ofihe
                   considerably lower, and shorelines                                                                                                       jetties is oblique
                                                                                                                                                            conipared with the
                   were many miles to the west of their
                                                                                                                                                            trend ofthe
                   present positions. The shoreline was                                                                                                     shoreline. (From
                                                                                                                                                            Komar et al.
                   then on what is now the continental                                                                                                      [1976b])
                   shelf, and the beaches were
                   backed by a smooth coastal
                   plain. At that time, sand de-
                   rived from rivers draining the                                                    YAQUINA BAY                          JETTIES
                   Klamath Mountains could                                                                    tember       1974
                   move northward as littoral
                   drift without being blocked by
                   headlands. Studies of heavy
                   minerals contained within
                   continental-shelf sands dem-
                   onstrate that this was the case
                   (Scheidegger et al. 197 1 @-the
                   metamorphic minerals from
                   the Klamaths can be found in
                   the shelf sands nearly as far
                   north as the Columbia River. As the Klamath-                        the Washington continental shelf. Some Colum-
                   derived sand moved north, additional sand was                       bia River sand did move south along the Oregon
                   contributed to the beaches by rivers draining the                   beaches during lowered sea levels, mixing with
                   Coast Range; thus, there is progressively more                      the sand from the Klamath Mountains and Coast
                   augite and a lower proportion of metamorphic                        Range.
                   minerals from the Klarnaths. The Columbia River                         The absence of headlands during lowered sea
                   was a source of much sediment, but most of that                     levels permitted an along-coast mixing of sands
                   sand moved to the north; as a result, it dominates                  derived from multiple sources, principally from
                   the mineralogy of ancient beach sands found on                      the Klamath Mountain metamorpliics, the


                                                                                                                                                    51







                                                                                           1988b). The pattern of along-coast mixing of
                                                                                           sand from the various sources, established during
                                  hypersthene (45%)                                        lowered sea levels, is still partly preserved within
                                  ougite (19 %)
                                  green hornblende (14%)                                   the series of pocket beaches now separated by
                                  brown hornblencle (9*/o)             6'-,                headlands. Therefore, one can still find minerals
       Figure 15: The             enstitite (4                                             derived from the Klamath Mountains in virtually
                                  z i rcon (2 %)
       principal sources of       clear garnet (2%)                                        all of the beaches along the Oregon coast, even
       sand to Northwest                                                            e r
       beaches are the                                                                     though it is certain that the sand can no longer
       Columbia River, the
                                                                                           pass around the many headlands that separate
       Coast Range                                                     Z
       mountains, and the         ougite                                                   those beaches from the Klarnaths. In most cases,
       Klamath Mountains.         brown hornblencle                                        that Klamath-derived sand could have reached
       Each source supplies
                                                                      U)                   the modem beach only by along-coast mixing
       different suites of                                            -Z
       heavy minerals to the                                          0                    during lowered sea levels and subsequently mov-
       beach and estuarine        glaucophone                         U                    ing onshore with the rise in the sea level at the
       sands. (From               pink garnet
       Clemens and Komar          green hornblende                                         end of the ice ages. However, there has been
       [(1988b])                  brown hornblencle                                        some modification of the beach-sand mineralogy
                                  hypersthene
                                  ougite                                                   from that along-coast mixing pattern as local
                                  epiclote                                                         have contributed sand to the beaches
                                                                                           sources
                                  zircon
                                                                                           during the last few thousand years. Such beach-
                                  cliopside
                                  stourolite                                               sand sources include sea-cliff erosion and some
                                  olivine                                                  sand derived from rivers and streams entering the
                                                                                           isolated pocket beaches.
                                                                                             There can be distinct changes in beach-sand
                              Coast-Range volcanics, and the Columbia River.             mineralogies on opposite sides of headlands, that
                              Depending on the location along this former                is, within adjacent but isolated pocket beaches or
                              shoreline of the Oregon coast, the beach consisted         littoral cells (Clemens and Komar 1988a, 1988b).
                              of various proportions of mineral grains from              One such change is found at Cascade Head north
                              these sources. Although a portion of the beach             of Lincoln City and continues at Cape
                              sand was left behind during the rapid rise in sea          Foulweather further south. To the north of Cas-
                              level and now can be found on the continental              cade Head the beach sand is rich in augite, which
                              shelf, some of it migrated landward with the               came either from the local rivers and streams
                              transgressing shoreline. Because the beaches               draining the Coast Range or from sea-cliff ero-
                              would have been low in relief, storm waves were            sion which cuts into alluvium derived from that
                              able to wash over them, transporting sand from             same volcanic source. In contrast, to the south of
                              the ocean shores to the landward sides of the              Cascade Head the augite content of the beach
                              beaches and thereby producing the migration.               sand is much reduced. Sea cliff erosion is of obvi-
                              Additional sand was obtained from the various              ous importance there, but these cliffs are cut into
                              river sources and from sediments eroded from the           a marine ten-ace that contains sands of ancient
                              coastal plain.                                             beaches and dunes that have been uplifted.
                                 About five to seven thousand years ago, the             Analyses completed on the mineralogy of those
                              rate of rise in sea level decreased as the water ap-       terrace sands indicate that they are also composed
                              proached its present level. At about that time, the        of mixtures of Klamath Mountain, Coast Range,
                              beaches of Oregon came under the influence of              and Columbia River sands (Clemens and Komar
                              headlands that segmented the formerly continu-             1988a). Apparently these terrace deposits also
                              ous shoreline. At some stage several thousand              record an along-coast mixing of sediments at
                              years ago, the headlands extended into suffi-              lowered sea levels, a mixing that was preserved
                              ciently deep water to hinder further along-coast           much as it has been on the modem beaches. This
                              transport of the beach sands. This is shown by a           has an unfortunate aspect in that it makes it virtu-
                              study of the mineralogy of sand found on the               ally impossible to distinguish what portion of the
                              present-day beaches (Clemens and Komar 1988a,              sand on the modem beach in that area has been

                              52







                contributed by recent cliff erosion and what sand
                moved onshore during the last rise in sea level.
                At any rate, the change in beach-sand mineralogy                       river
                on opposite sides of Cascade Head does demon-                                              CIO
                strate the effectiveness of that headland in isolat-                                               BIA          Figure 16: Changes
                                                                                                                 R              in the degree of
                ing the adjacent pocket beaches. It also shows                                                                  rounding of the beach
                that recent contributions to the beaches have been          %                beach                              sand on opposite
                sufficient to alter the pattern established by               50@r@                                              sides of Tillamook
                                                                              0
                along-coast mixing during lowered sea levels.                   VAASA SRR WR                                    Head, with more
                                                                                                                                angular grains to the
                   A still more dramatic change in the beach sand                                                               north due to their
                occurs at Tillamook Head, south of Seaside, fig-                                                                recent arrivalfrom
                                                                                                beach
                                                                                                                                the Columbia River
                ure 16 (Clemens and Komar 1988a, 1988b).                                                                        (VA = very angular,
                North of this headland the beach sand is derived                                                                A = angular, SA
                almost entirely from the Columbia River, and the                             TILLAMOOK                          subangular, SR
                                                                                               HEAD                             subrounded,R
                abundant supply of sand from that large river has                                                               rounded,and WR
                built the shoreline out significantly within his-                                                               well rounded). (After
                                                                                               beach                            Clemens and Komar
                toric times. South of the headland the beach sand                                             AUGITE            11988a])
                is abundant in augite, again indicating a Coast                                beach         ROUNDING
                Range source from local rivers or cliff erosion.                                                5krn
                This beach sand also contains small amounts of
                Klamath Mountain minerals, the farthest north                             CAPE FALCON
                the relict pattern of along-coast mixing during
                lowered sea levels can be found preserved in the
                modem beaches. There is some Columbia River             significant fisheries, and, as will be discussed
                sand in this beach to the south of Tillamook            here, play a central role in sediment movements
                Head, but it got there by mixing southward with         on the coast which govern contributions of sand
                sands from the other sources during lowered sea         to the beaches.
                level and then migrating onshore. That Columbia-           An estuary is a zone of complex mixing of
                derived sand has been on the beach for thousands        fresh water from the river with salt water from the
                of years, whereas to the north of the headland the      ocean. The fresh water is less dense and therefore
                beach sand came from the Columbia within the            tends to flow over the top of the seawater. At
                last century or two. This contrasting history of the    times, much of the fresh water from the river
                beach sands is also indicated by the degree of          flows through the entire estuary and enters the
                rounding of the individual grains, as shown in          ocean before it finally mixes with the underlying
                figure 16. North of the headland the grains are         sea water. In such a case, the lens of salt water at
                fresh in appearance and angular, attesting to their     depth within the estuary has a net flow from the
                recent arrival from the Columbia--the grinding          ocean into the estuary. This is significant since it
                action of the surf has not had sufficient time to       is one mechaiiisin that transports sediment from
                abrade and round the grains. To the south of the        the ocean into the estuary and inhibits the river
                headland the grains are much rounder, their sharp       sands from reaching the ocean beaches, the situa-
                edges having been worn away during thousands            tion found in many Northwest estuaries.
                of years of movement beneath the swash of                  The restriction of sand movement through
                waves on the beach.                                     Northwest estuaries was first demonstrated in a
                   During low stands of sea level, the coastal          study of sediments within Yaquina Bay (Kuhn
                rivers were able to cut down their valleys. When        and Byrne 1966). Similar to the other rivers
                the water rose at the end of the ice age, these         draining the Coast Range, the Yaquina River
                valleys were drowned and developed into                 trarisports sand containing augite as its principal
                estuaries. These estuaries are important, serving       heavy mineral. This sand contrasts with the beach
                as harbors and the centers of many coastal              sand outside of the bay that contains a large vari-
                communities. They are also environments of              ety of minerals, including the metamorphic

                                                                                                                          53







                                  minerals derived from the Klamath Mountains. In                     Another implication of the results in figure 17
                                  addition, some of the quartz and feldspar grains                is that little if any sand from the Yaquina River is
                                  on the beach are coated with red iron oxide (these              currently reaching the ocean beach. This conclu-
                                  grains are probably from sea-cliff erosion of the               sion applies only to sand-sized grains. The fine
                                  marine terraces); such coated grains are not found              clays that remain in suspension in the water are
                                  in the Yaquina River. These differences make it                 carried into the ocean. Their presence is evident
                                  possible to trace the movement of the river and                 by the brown plumes that emanate from the inlet
                                  beach sands entering the estuary. The result is                 during river floods. Most of the major coastal riv-
                                  sunimarized in figure 17 from Kulm and Byrne                    ers, are separated from the ocean by large estuar-
                                                                                                           ies and thus are not Rely to contribute a
                                                  NEWPORT
                                                                                                N          significant amount of sand to the modem
                                                                                                           beaches. This in part explains why many
                                                                                                           of the Oregon beaches have a relatively
        Figure 17: Sediment
                                                                                                           small volume of sand and why their
        patterns within
        Yaquina Bay,                                                                            I k.       mineralogies still reflect the along-coast
        illustrating the                           1868                                                    mixing of sand sources during low stands
                                                 Shoreune
        mixing of marine                                                        Realms          of Deposition
        sands carried into                                                                                 of sea level rather than more recent contti-
                                                                                    MI marine
        the estuary by tidal                                                                               butions.
                                                                                                mixed
        flows andfluvial
        sandsfrom the river.                                                        EM fluviotile             Such pattems of sand deposition have
        (After Kulm and                                                                                    been shown to occur for other major estu-
        Byrne 11966])                  YAQUINA BAY                                                         aries of the Northwest (Scheidegger and
                                       OREGON                                                              Phipps 1976; Peterson et al. 1984). How-
                                       (Kulm and Byrne, 1966)                                              ever, a study of the small Sixes River of
                                                                                                           Oregon, which does not really have an es-
                                                                                                           tuary, indicates that it supplies sand to the
                                  (1966), where it is seen that the river sand (fluvia-           adjacent beach, although the amounts would be
                                  tile) forms 100% of the estuarine sediment in                   minor given the small size of that river (Boggs
                                  only the landward portion of Yaquina Bay. Ma-                   1969; Boggs and Jones 1976). In general, the ma-
                                  rine sand has been carried into the bay through                 jor rivers have sufficiently large estuaries that it is
                                  the inlet and dominates the estuarine sediments                 doubtful whether much, if any, river sand reaches
                                  near the mouth. Much of the bay is a zone where                 the adjacent beaches. The one clear exception to
                                  the river and marine sands are mixed in varying                 this is the Columbia River, which transports more
                                  proportions. The results indicate that Yaquina                  than 100 times as much sand as the next largest
                                  Bay is slowly being filled with sediment-fluvia-                river (the Umpqua) and on the order of 1,000
                                  tile sands from the land and marine sands from                  times as much sand as other coastal rivers
                                  the ocean. This activity has also been shown for                (Clemens and Komar 1988a).
                                  Alsea Bay where drilling through the sediments
                                  indicates that the bay began to fill immediately
                                  after the formation of the estuary with the last rise           Case Studies of Sand Spit Erosion
                                  in sea level and is continuing to fill (Peterson et                The most dramatic occurrences of erosion on
                                  al. 1982, 1984a). Becoming filled with sediments                the Oregon coast have centered on the sand spits.
                                  is generally the fate of estuaries. Having devel-               The causative factors have ranged from jetty con-
                                  oped by the drowning of river valleys at the end                struction at Bayocean Spit, to the natural pro-
                                  of the ice age, estuaries represent an environment              cesses of waves and currents at Siletz and
                                  that is out of equilibrium. As a result, an estuary             Nestucca Spits, to extreme examples of erosion at
                                  tends to fill until it is reduced to a river channel
                                  that is able to transport all of its sediments to the           Alsea and Netarts Spits initiated during the 1982-
                                  ocean. Such a development involves thousands of                 83 El Nifio.
                                  years, so we should not view our estuaries as
                                  ephemeral features.

                                  54







                Jetty Construction and the Erosion of
                Bayocean Spit                                                                  Manhatien Beach
                  The story of Bayoccan Spit is of particular in-
                terest in that it provides the earliest example on
                the Oregon coast of a failed attempt at major de-                              Rockaway Beach
                velopment and also of the erosive impacts associ-
                ated with jetty construction (Terich and Komar
                1974; Komar and Terich 1976). The San Fran-                             C
                                                                                        0
                                                                                        cu
                cisco realtor T.B. Potter was attracted to                                                                     Figure 18: Schematic
                Tillamook Bay during a fishing trip in 1906 and                         0                                      diagram illustrating
                                                                                                            J:.                the patterns of erosion
                vowed to build the "Atlantic City of the Pacific
                                                                                                                               and accretion in
                                                                                                   jetty
                Coast" on the spit separating the Bay from the                N                                                response to
                                                                                        .U                                     constraction of the
                ocean. His vision soon took form with the con-                                                                 north jetty at the inlet
                struction of an elegant hotel, a natatorium that                                                               to Tillamook Bay.
                                                                                        0
                housed a heated swimming pool with artificial                                                                  Sand that carnefrom
                                                                                                                               erosion along the
                surf, a number of permanent homes, and a "tent                                         a
                                                                                                              1#               length of Bayocean
                                                                                                                               Spit accumulated to
                city" for summer visitors. The downtown con-                                                                   form an extensive
                tained a grocery, bowling alley, and agate shop.                                                               shoal at the mouth of
                However, the development soon ran into eco-                                                          Co        the inlet.
                                                                        0     1    2    3
                                                                                                                    0
                nomic problems as lots did not sell at the hoped                krn
                for rate, primarily because of the inaccessibility
                of the area and delays in construction of the rail-               M erosion
                road from Portland. But the chief threat came                     E3 deposition
                from erosion caused by jetty construction in
                1914-17 at the mouth of Tillamook Bay (figure
                18). Because of economic constraints, only a                               Cape
                north jetty was completed at that time (the south                         Meares
                jetty was not built until 1974), and this turned out
                to be critical to the magnitude of the resulting       retreated, dropping houses, the natatorium (figure
                erosion. The overall pattern of sand movement          19), and finally the hotel into the surf. A stonn
                and shoreline changes was similar to that de-          during November 1952 brought the final demise
                picted schematically in figure 13B, but it was         of the development, breaching the spit at its nar-
                made more complex by the fact that only one            rowest point. This breach was diked by the Corps
                jetty was constructed. Sand quickly accumulated        of Engineers in 1956, rejoining what had become
                north of the jetty, figure 19, with the shoreline      an island to the mainland. All that remains of
                building out At the same time, sand accumulated        Potter's development are slabs of concrete foun-
                to the south but formed a shoal within the mouth       dations that now litter the beach.
                of the inlet, greatly increasing the hazards to navi-  Natural Processes and the Erosion of Siletz
                gation. The sand that formed the shoal was de-         and Nestucca Spits
                rived from erosion along the length of Bayoccan           The erosion of Siletz and Nestucca Spits pro-
                Spit. It is likely that some of the sand brought to    vides examples of the impacts of natural pro-
                the shoal was carried into the bay and perhaps to      cesses-the combined effects of storm waves, rip
                the offshore, so that erosion of Bayocean Spit         cuffents and elevated water levels (Komar and
                continued for many years rather than reaching a        Rea 1976; Komar and McKinney 1977; Komar
                new equilibrium as is possible where two jetties       1978, 1983a). The development of Siletz Spit be-
                are constructed (figure 13B). The erosion of           gan in the 1960s with the construction of a
                Bayocean was most rapid during the 1930s and           number of homes, many within foreduries
                1940s following reconstruction and lengtheruing        immediately backing the beach. The first major
                of the north jetty. The ocean edge of the spit         episode of erosion leading to property losses

                                                                                                                          55










                                                                            1910






                                                                                                                                     r





       Figure 19: The                                                          32
       progressive erosional
       destruction of the
       Natatorium on
       Bayocean Spit.
       (Photosfrom The
       Tillamook Pioneer
       Museum)
                                                                                                         a,-@t4i -k,-@J,





                                                                                               Ir
                                                                         1940







                                                                                                4


                                                                                           Figure 20: Erosion on Siletz Spit during December 1972.
                                                                                           One house under construction was lost, while others ended
                                                                                           up on promontories ofriprap extending into the surf as
                              occurred during the winter of 1972-73. One                   adjacent enWty lots were left to erode,
                              house under construction was lost, figure 20,
                              while others ended up on promontories extending              positions (we do not know what controls the loca-
                              into the surf zone when riprap was first installed           tion of tip currents and therefore cannot predict
                              along their seaward fronts and then on their                 where the erosion will occur). In the meantime,
                              flanks as adjacent empty lots continued to erode.            earlier "bites" taken out of the foredunes by rip
                              The main factor in that erosion episode was the              currents and storm waves would fill in with drift
                              occurrence of major storm waves, the 23-foot                 logs which in turn captured wind-blown sands so
                              significant wave heights of December 1972 in the             the dunes quickly reformed. This cycle of dune
                              microseismometer record of figure 5. However,                erosion and reformation occurred repeatedly on
                              the erosion was limited to only a small portion of           Siletz Spit, with no measurable long-term net
                              the spit, detennined by the presence of a tip                retreat of the seaward edge of the foredunes on
                              current that had hollowed out an embayment in                the spit The principal mistake made in devel-
                              the beach so that waves were able to reach the               oping Siletz Spit was to build homes in this zone
                              foredunes and houses (figure 21). A series of                of foredunes susceptible to periodic erosion. We
                              aerial photographs of Siletz Spit revealed the               quickly became aware of this during the erosion
                              repeated occurrence of such erosion events over              of 1972-73 (figure 20)--the erosion exposed drift
                              the years. In general, during any particular winter          logs within the heart of the spit, often beneath
                              the erosion would occur in only one or two loca-             homes built in the 1960s. These drift logs had
                              tions determined by the largest rip-current em-              been cut by saws. What clearer indication could
                              bayments. In subsequent winters the erosion                  one have of the ephemeral nature of the sites
                              shifted to other areas as the rip currents changed           where these homes had been built?


                              56







                    Siletz Spit has repeatedly eroded
                 during subsequent winters, but each
                 time more riprap has been added so
                 that the properties are now reasonably
                 secure. Lots lost to erosion have been
                 filled with beach sand and leased again
                 for development.
                    Large storm waves combined with                                                                                            Figure 21: Rip
                                                                                          41                                                   currents cutting
                 high spring tides during February 1978                                                                                        embayments through
                 to cause extensive erosion in many ar-
                                                                                                                                               the beach and
                 eas of the Oregon coast (Komar 1978).                                                                                         reaching the
                                                                                                                                               development on
                 The greatest impact occurred along                                                                                            Siletz Spit during
                 Nestucca Spit on the northern Oregon                                                                                          December 1972. The
                 coast, where an uninhabited area of the                                                                                       large embayment
                                                                                                                                               seen in the upper
                 spit was breached and foredune erosion                                                                                        photograph was the
                 threatened a new development in                                                                                               center of property
                                                                                                                                               losses photographed
                 which houses were still under construc-                                                                                       infigure 20.
                 tion (figures 22 and 23). Storm waves
                                              -current
                 again combined with rip
                 embayments to control the zones of
                 maximum erosion along the spit and
                 detennine the area of breaching. How-
                                                                       P                                                t4_
                                                                                _W1_ F-771
                 ever, of particular importance to the
                 erosion was the simultaneous occur-
                 rence of high perigean spring fides and
                 a storm surge wliich raised water levels
                 by some 8 to 9 inches above predicted
                 tide levels. Spring fides occur when the
                 moon, earth, and sun line up so the
                 gravitational forces causing the tide su-
                 perimpose, producing the highest
                                                                                                      4
                                                                                                               4
                 monthly tides. A pefigean spring tide
                 occurs when the moon comes closest to
                 the earth in its eliptical orbit, so that the
                 fide-producim force is still greater than
                                                                                                                                               Figure 22: The
                 during normal spring tides. Typical                                                                                           breaching of
                 spring fides on the Oregon coast reach                                                                                        Nestucca Spit during
                                                                                                                                               the February 1978
                 +9 feet MLLW, while pedgean spring
                                                                                                                                               storm at a time Of
                 tides achieve +10 feet MLLW (MLLW
                                                                                                                                               perigean spring tides.
                                                                                                                                               (Pholofrom Oregon
                 denotes "mean lower low water," the                                                      _V W."N                              State Highway
                 average of the lowest daily tides, which                                                                                      Department)
                 is taken as the 0 reference tidal eleva-
                 tion). Measured high tides reached
                 +10.2 feet MLLW at the time of the
                 February 1978 storm that eroded
                 Nestucca Spit, unusually high for the
                 Oregon coast and substantially higher
                 than fides during the December 1972
                                                                             4@
                 erosion of Siletz Spit. It was this



                                                                                                                                       57








                                                                                                          on the foreduries at Kiwanda Beach at the
                                                                                                          north end of Nestucca Spit (figure 23,
                                                                                                          upper). Like the erosion of Siletz Spit,
                                                                                                          drift logs were exposed within the erod-
                                                                                                          ing dunes, some of which had been
                                                                                                          sawed. However, these logs were more
        Figure 23: (Upper)                                                                                rotten than those found within Siletz Spit,
        Riprap placed to                                                                                  suggesting that erosion episodes on
        protect homes under
        construction at                                                                                   Nestucca Spit are less frequent. This
        Kiwanda Shores on
                                                                                                          lower frequency of erosional occurrences
        Neslucca Spit in
        response to erosion                                                                               at Nestucca Spit is probably due to its
        during February                                                                                   beach being finer grained than at Siletz;
        1978. (Lower) The                                                                                 as I explained earlier, coarser-sand
        subsequent
        accumulation of dune                                                                              beaches respond more rapidly and to a
        sands, completely
                                                                                                                                     -wave conditions.
                                                                                                          greater degree to storm
        covering the riprap
                                                                                                          Nestucca Spit began to mend during the
        and becoming a
        problemfor the
                                                                                                          summer following its erosion. As was the
        homes (1988 photo).                                                                               case with the dune reformation on Sfletz
                                                                                                          Spit, drift logs accumulated within the
                                                                                                                                                -blown
                                                                                                          breach and helped to trap wind
                                                                                                          sand. So much sand has returned to the
                                                                                                          beach fronting the housing development
                                                                                                          at Kiwanda Beach that the masses of
                                                                                                          nprap are now buried and the oveirabun-
                                                                                                          dance of sand has become a problem
                                combination of a major storm and perigean high                            (figure 23, lower).
                                tides that resulted in the unusual occurrence of                The 1982-83 El Nifio-An Unusual Erosion
                                breaching at Nestucca Spit. The only other spit                 Event
                                breaching known to have occurred during historic                   A decade ago, an El Nifio was thought to in-
                                times was at Bayocean Spit, and that breach was                 volve only a shift in currents and a waiming of
                                due to jetty construction rather than natural                   ocean waters to the west of South America. Its
                                causes. There are frequent occurrences of breach-               occurrence was primarily of interest because an
                                ing and washovers on spits and barrier islands of               El Nifio caused the mass killing of fish off the
                                the east and Gulf coasts of the Uiiited States due              coast of Peru. No one imagined that an El Nifio
                                to the subsidence of those areas adding to the glo-             had wide-ranging consequences, including play-
                                bal rise in sea level. However, the Northwest                   ing a major role in beach erosion along the west
                                coast is rising tectonically, so there is minimal               coast of the United States. This awareness came
                                transgression of the sea over the land, and this                during the El Nifio of 1982-83, an event of un-
                                probably accounts for the rarity of spit breaching              usual magnitude, when erosion problems were
                                here. It took the unusual circumstances of the                  experienced along the shores of Califomia and
                                February 1978 storm to produce a breac                   gh     Oregon. The natural processes usually involved
                                perigean spring tides with a significant storm                  in beach erosion also played a role during the
                                surge, exceptionally energetic storm waves, and                 1982-83 El Nifio, but generally at much greater
                                the development of a major rip-current embay-                   intensities than normal. In addition, there were
                                ment that by chance focused the erosion along the               unusual effects that enhanced the overall erosion
                                thinner section of the spit.                                    problems and caused them to continue well be-
                                    When the stonn struck in February 1978, a de-               yond 1982-83.
                                velopment of new houses was under construction




                                58







                   It once was thought that the onset of El Nifio          reached Callao on the coast of Peru in January
                 off Peru was caused by the cessation of local             1983. The water-level changes associated with
                 coastal winds which produce upwelling. This               these sea-level waves during an El Nifio are very
                 view changed when it was demonstrated that
                 these local winds do not necessarily diminish dur-
                 ing an El Niijo; rather, it is the breakdown of the            20-
                 equatorial trade winds in the central and western
                 Pacific that triggers an El Nifio. During nonnal
                                                                                0- - ----
                 periods of strong southeast trades, there is a sea-                 Rabaul
                 level setup in the western equatorial Pacific with             - 4-S , 152-W
                 an overall east-to-west upward slope of the sea
                 surface along the equator. The same effect is ob-              20-  Fanning                                           Figure 24: The
                 tained when you blow steadily across a cup of                  -  4* N, 159*W                                         sea-level "wave"
                 coffee-the surface of the coffee becomes high-            -E   o                                                      during the 1982-83
                                                                           &                                                           El Niho nwasured
                 est on the side away from you. If you stop blow-          Z    -                                                      at a sequence of
                 ing, the coffee surges back and runs up your side         >                                                           islandsfrom west
                                                                           Q)   -                                                      to east near the
                 of the cup. The process is similar in the ocean           0
                                                                           W                                                           equator, and
                 when the trade winds stop blowing during an El                 '0 Santa Cruz                                          finally at Callao on
                 Nifio. The potential energy of the sloping water                    I-S,90-W                                          the coast ofPeru.
                                                                                                                                       (After Wyrtki
                 surface is released, and it is this release that pro-          a--                                                    11984])
                 duces the eastward flow of warm water along the
                 equator toward the coast of Peru, where it kills                    Callao
                 fish not adapted to warm water. Associated with                20- 12-S,77-W
                 this movement of warm water eastward along the                 -
                 equator is a wavelike bulge in sea level. The Co-              0
                 riolis force, which results from the rotation of the
                 earth on its axis, causes currents to tum to the
                 light in the northern hemisphere and to the left in            Jan.      Apr. 1982  July      Oct.       Jan 1983
                 the southern hemisphere. Since this released wa-
                 ter during an El Nifio flows predominantly east-          large (figure 24). They typically involve varia-
                 ward along the equator, the Coriolis force acts to        tions up to 50 centimeters (20 inches) and take
                 confine the wave to the equatorial zone, con-             place within a relatively short period of time, 4 to
                 stantly turning it in toward the equator. This pre-       6 months. Translated into an annual variation, this
                 vents the dissipation of the sea-level high by its        is equivalent to a rate of approximately 1,000 mil-
                 expansion to the north and south away from the            limeters a year, far in excess of the I to 2 milli-
                 equator. The eastward progress of the sea-level           meters a year global rise in sea level caused by
                 wave can be monitored at tide gauges located on           the melting of glaciers.
                 islands near the equator (Wyrtki 1984). As dis-                With its arrival on the coast of South America,
                 cussed earlier, measurements from a Ode gauge             the sea-level wave splits, and the separated parts
                 can be averaged so as to remove the tidal fluctua-        respectively move north and south along the
                 tions, yielding the mean sea level for that period        coast. Now the wave is held close to the coast by
                 of time. Sea-level variations at islands along the        the combined effects of the Coriolis force and re-
                 equator during the 1982-83 El Nifio are shown in          fraction of the wave over the inclination of the
                 figure 24. From these tide-gauge records one can          continental slope. This again prevents the sea-
                 easily envision the passage of the released sea-          level high from flowing out to sea and dissipat-
                 level wave as it traveled eastward across the Pa-         ing. Analyses of tide-gauge records along the
                 cific. Its crest appears to have passed Fanning           coast have demonstrated that sea-level waves can
                 Island south of Hawaii in late August and Santa           travel as far north as Alaska (Enfield and Allen
                 Cniz in the Galapagos at the end of the year, and         1980). The analyses have also shown that as the


                                                                                                                              59







                                 sea-level wave travels northward, it loses rela-                may significantly raise water levels for several
                                 tively little height at the coastline itself. The Co-           months.
                                 riolis force increases in strength at higher                       Figure 25 shows the monthly mean sea levels
                                 latitudes, so the wave hugs the coast more tightly              measured by the tide gauge in Yaquina Bay dur-
                                 and thereby maintains its height, even though it                ing the 1982-83 El Niflo (Huyer et al. 1983;
                                 may lose some of its energy. The wave travels at                Komar 1986). Sea level reached a maximum dur-
                                 a rate of about 50 miles a day, and so quickly                  ing February 1983, nearly 60 centimeters (24
                                 reaches California and Oregon following its in-                 inches) higher than the mean water surface in
                                 ception at the equator. The water-level changes                 May 1982, nine months earlier. The thin solid
                                 associated with these shelf-trapped sea-level                   line in the figure follows the ten-year means for
                                 waves are an important factor in beach erosion                  the seasonal variations, and the dashed lines give
                                 along the west coast of North America during an                 the previous maxima and minima measured in
                                 El Nifio.                                                       Yaquina Bay. These curves in part reflect the nor-
                                     In summary, one aspect of an El Nifto is the                mal seasonal cycle of sea level produced by par-
                                 generation of large sea-level variations which                  allel variations in atmospheric pressures and
                                 take the form of a wave that first moves eastward               water tempenitures. However, it is apparent that
                                 along the equator and then splits into poleward-                the 1982-83 sea levels were exceptional, reaching
                                 propagating waves when it reaches the eastern                   some 10 to 20 centimeters higher than previous
                                 margin of the Pacific Ocean. These basinwide                    maxima, about 35 centimeters (14 inches) above
                                 responses involve several months of wave travel,                the average winter level. Much of this unusually
                                 and at any given coastal site the sea-level wave                high sea level can be attributed to the effects of a
                                                                                                            coastally trapped sea-level wave gener-
                                     70     1     1     1   1       1 1    1     1    1      1   1   1      ated by the El Niflo.
                                     r.0 - SEA LEVEL                                                   -       Wave conditions on the Oregon coast
                                           Newport, Oregon
                                     50 -                                                              -    were also exceptional during the 1982
                                 W
                                 W                                                                          83 El Nifio (Komar 1986). Figure 26
                                 -j  40-
                                                                                                            shows the daily measurements from the
                                 uj
                                 Zn  30
                                 0                                                                          microseismometer at Newport, collected
                                 W
                                     20                                                                     from August 1982 through April 1983.
                                                                                                            There were several storms that generated
                                     10 -
                                                                                                            high-energy waves, three achieving
                                     0   M     i        i A     S   0   N     D     i        FM   A     m   breaker heights on the order of 20 to
                                                        1982                                 1983           25 feet.
                                 Figure 25: (Above)
                                 Monthly sea levels
                                 measured with the                  8        1                   1
                                 tide gauge in Yaquina
                                 Bay. The recordftom                7 -
                                 the 1982 -83 El Niho
                                 year (dols) shows              -13
                                                                @;  6 -
                                 that water levels
                                 exceeded all previous
                                 records (mean values           3f  5
                                 given by the solid
                                 curve, the previous                4-
                                 maxima and minima
                                                                W
                                 by the dashed lines).              3-
                                 (From Huyer et al.
                                 [1983] and Komar
                                                                W   2 -
                                 119861)                        Cr
                                                                Co
                                 Figure 26: (Right)
                                           S
                                           N
                                            E
                                            e
                                              A
                                              wpo"t
                                                  L
                                                        E
                                                        0
                                                        V
                                                        E
                                                        ,eg
                                                        L
                                                        on
































                                 Wave breaker-height
                                 measuremenisfrom
                                 Newport during the                 0
                                 1982-83 EINihoperiod.                AUG.       SEPT.       OCT.   NOV.      DEC.       JAN.      FEB.     MARCH     APRIL
                                 (From Komar 119861)                                         1982                                     1983

                                 60







                  The erosion which occurred on the Oregon
               coast during the 1982-83 El Nifto was in response            CAPE FOULWEATHER
               to these combined processes. The large storm                                                          N
               waves that struck the coast arrived at the same                                                Ikm
               time as sea level was approaching its maximum
               (figures 25 and 26). High spring tides were also a                                            OTTER
               factor. During the December 1982 storm, high                                                  ROCK
               tides reached +11.0 feet MLLW, 23 inches higher
               than the predicted level due to the raised sea                   Sand Accumulation
               level. The tides during the January 1983 storm                  and Shoreline Buildout
               were still more impressive, reaching + 12.4 feet,
               34 inches higher than predicted. This pattern con-                                             BEVERLY
               tinued during the February 1983 storm when high                                                 BEACH
               tides up to + 10. 3 feet were measured, 17 inches
               above the predicted level. All of these high tides                     1982-83 Longshore
               represent exceptional water elevations for the                          Sand Transport
               coast of Oregon.
                  As expected, the intense storm activity and
               high water levels during the winter of 1982-83
               cut back the beaches of the Oregon coast. How-
               ever, for a time the pattems of erosion were puz-             Sand Losses with
               zling. There were numerous reports of erosion                   Beach Erosion
               problems along the coast, yet beaches in other
               areas were building out. It took some time to de-
               termine what was happcning. As discussed ear-                    YAQUINA
               lier, the summer waves normally approach from                      HEAD                       AGATE
               the nofthwest while the winter waves arrive from                                              BEACH
               the southwest, so there is a seasonal reversal in                     Sand Accumulation with
               sand transport directions along the beaches. Over                     Shoreline Buildout and
               the years there is something of an equilibriurn                       Dune Development
               between the north and south sand movements
               within any pocket, yielding a long-term zero net
               littoral drift. This equilibrium condition was upset
                                                                      r1gure27: The patterns of beach erosion and accretion
               during the 1982-83 El Nifto because of the south-      during the 1982 -83 El Nifio, resultingfrom the northward
               ward displacement of the storm systems. The            transport of sand within the littoral cell. (From Komar
               waves approached the Oregon coast from a more          119861)
               southwesterly direction, and Us, together with
               the high wave energies of the storms, caused an        headland the beach eroded down to bedrock
               unusually large northward movement of sand             (figure 28 upper), while south of it at Agate
               within the beach cells (figure 27). The resulting      Beach so much sand accumulated it formed a
               effect was one of sand erosion at the south end of     large field of dunes (figure 28 lower). People who
               each pocket beach and deposition at the north.         had the misfortune to live north of the headlands,
               This can be viewed as the reorientation of the         at the south ends of the pocket beaches, exper-
               pocket beaches to face the waves arriving from         ienced some of the greatest beach and property
               the southwest, or as any one headland acting like      losses along the coast. There the beaches eroded
               ajetty so that it blocks sand on its south and         to a greater degree than duriDg normal winters,
               causes erosion to its immediate north. This pat-       the sand not only moving offshore to form bars,
               tem is illustrated in figure 28 for the beaches        but also northward along the shore. Having lost
               north and south of Yaquina Head. North of that         the buffering protection of the fronting beaches,


                                                                                                                       61







                                                                                                                    Niflo. It was the northward growth of
                                                                                                                    this bar that diverted the channel from
                                                                                                                    its normal course.
                                                                                                                        The erosion experienced on Alsea
                                                                                                                    Spit, which continued for about three
                                                                                                                    years, can be directly attributed to this
                                                                                                                    northward deflection. of the channel.

        Figure 28: Beaches
                                                                                                                    The earliest property losses on the spit
        north and south of                                                                                          were during the winter of 1982-83 and
        Yaquina Head                                                                                                occurred on its ocean side well to the
        during the 1982-83
        El Nifio, with a total                                                                                      north of the inlet. The focus of this
        depletion of sand to                                                                                        erosion was directly landward of where
        the north (upper) and
        large quantities of                                                                                         the charmel turned toward the sea
        sand accumulated to                                                                                         around the end of the northward-
        the south on Agate
                                                                                                                    extending offshore bar. Erosion there
        Beach (lower).
                                                                                                                    appeared to hee caused by the over-
                                                                 11ptir               'ROW,
                                                                                                                    steepened beach profile leading into the
                                                                                                                    deep channel, and by direct wave
                                                                                                                    attack-waves passing ffirough this
                                                                                                                    channel did not break over an offshore
                                                                                                                    bar, and therefore retained their full
                                                                                                                    energy until breaking directly against
                                                                                                          I         the properties on the spit. The erosion
                                                                                                                    continued for more than three years
                                                                                                                    with losses of property as the deflected
                                  properties north of headlands suffered direct                       channel slowly migrated southward towards its
                                  attack by storm waves, in many areas resulting in                   more-normal position. The photograph of figure
                                  considerable erosional losses.                                      29 was obtained during July 1985, by which time
                                      The area that suffered the greatest erosion dur-                significant migration had already taken place
                                  ing the 1982-83 El Nifio was Alsea Spit on the                      from the most northerly position of the opening
                                  central-Oregon coast (Komar 1986). The erosion                      during the winter of 1982-83. With this slow
                                  them was mainly in response to the northward                        southward movement of the opening, the focus of
                                  longshore movement of beach sand, a movement                        maximum erosion on the spit similarly shifted
                                  wl-dch deflected the inlet to Alsea Bay. Although                   south. In September 1985 there was an abrupt
                                  the problem originated during the 1982-
                                  83 El Niflo, the erosion continued for sev-
                                  eral years due to the disruption from
                                  normal conditions. During normal peri-
                                  ods, the charmel from Alsea Bay contin-
                                  ues directly seaward beyond the inlet
                                  mouth, but during the 1982-83 El Nifio                                                    OR",
                                  this channel was deflected well to the
                                  north, as seen in the photograph in figure
                                  29. There was little migration of the inlet
                                  mouth itself, the deflection instead taking
                                  place in the shallow offshore. Apparent in
                                                                                                                                                       im






                                  this photograph is an underwater bar ex-
                                  tending from the south, covered with                          Figure 29: The deflection of the channel leading into Alsea Bay
                                                                                                by the northward growth of the longshore bar in response to the
                                  breaking waves. The bar grew as a result                      1982-83 El Nifio-related storm waves arrivingftom the
                                  of the northward sand transport during El                     southwest. (From Komar 119861)

                                  62







                increase in the rate of erosion as the focus was        during the 1982-83 El Nifto came as a surprise.
                then on the unvegetated, low-lying tip of the spit      Being one of the smallest of the littoral cells on
                seen in figure 29. Wid-iin a couple of weeks, this      the coast, the pocket beach within the Netarts cell
                tongue extension of Alsea Spit completely eroded        underwent a marked reorientation due to the
                away. At the same time, the deep water of the off-      southwest approach of waves during the El Nifio.
                shore channel shifted landward, directly eroding        This depleted the beach of sand to the immediate
                the developed portion of the spit where it curves       north of Cape Lookout, leading to erosion of the
                inward toward the inlet Seven houses were               low-lying sea cliffs and sand dunes in that area.
                threatened by this erosion, particularly one that       However, of more lasting significance is that
                was adjacent to an empty lot initially left unpro-      much of the sand transported northward along the
                tected (figure 30).                                     beach was apparently swept through the tidal in-
                   The beach fronting Alsea Spit grew signifi-          let into Netarts: Bay; perhaps some moved off-
                cantly during the summer of 1986, and the tongue        shore as well. This effectively removed the sand
                of sand began to reform at the end of the spit.         from the nearshore zone, leaving the beach de-
                Erosion during the winter of 1986-87 was mini-          pleted of sand and thus less able to act as a buffer
                mal, so that Alsea Spit and the inlet to the bay        between park properties and storm-erosion pro-
                finally returned to their normal configurations,        cesses. Because of this, erosion problems on
                those which had prevailed for many years prior to       Netarts Spit have been endemic in recent years
                the 1982-83 El Nifio.
                   The effects of the 1982-
                83 El Nifio persisted still
                longer in the erosion of
                Netarts Spit (Komar et al.
                1988; Komar and Good
                1989). That erosion has
                been of particular concern
                in that its impact has been
                in Cape Lookout State
                Park, a popular recreation
                site. Netarts Spit forms
                most of the stretch of shore
                                                                                                                                 Figure 30: Erosion of
                between the large Cape
                                                                                                                                 A Isea Spit as a result
                Lookout to the south and
                                                                                                                                 of inlet deflection
                Cape Mears to the north                                                                                          during the 1982-83 El
                (figure 3 1). Erosion of                                                                                         Nifio. (From Komar
                Netarts Spit during historic                                                                                     (19861)
                times had been minimal.
                In the late 1960s a seawall
                was constructed at the
                back of the beach in the
                park area. Its construction                                "10AI
                was not entirely a response
                                                                                      444;1          14
                to wave-erosion problems,
                but in part to people walk-
                ing on the dune face and
                causing renewed activity
                of sand movement by
                winds. Therefore, the sud-                                                 A
                den and dramatic erosion







                                                                                                                  and have continued even though the
                                                                                                                  direct processes of the 1982-83 El Nifto
                                                                                                                  have ceased.
                                                                                                                      Rip currents and storm waves have
                                                                                                                  been the chief agents of erosion on
                                                                                                                  Netarts Spit. They cut back the beach
                                                                                                                  in the park area so that much of it was
                                                                                                                  covered by exposed cobbles rather than
        Figure 31: Netarts
        Spit and the inlet to                                                                                     sand (figure 32).'Ibe seawall was de-
        Netarts Bay, with                                                                                         stroyed, so that erosion of parklands
        Cape Lookout in the
                                                                                                                  became substantial. State Parks offi-
        background (March
        1978, Oregon State                                                                                        cials have considered placing riprap to
        Highway
                                                                                                                  prevent additional losses of parklands.
        Department).                                                                                              However, in subsequent winters the fip
                                                                                                                  currents could be positioned in other
                                                                                                                  areas along the spit, causing erosion
                                                                                                                  there. The more fundamental problem
                                                                                                                  is the depleted volume of sand on the
                                                                                                                  beach. To solve this, officials have con-
                                                                                                                  sidered a beach nourishment project,
                                                                                                                  the placement on the beach of sand
                                                                                                                  brought in from some other location.
                                                                                                                  Sand nourishment would restore the
                                                                                                                  beach along its full length, both in its
                                                                                                                  ability to act as a buffer and in its recre-
                                                                                                                  ational uses. Possible sources of sand
                                                                         . . . . . .                      JA      for such a nourishment project might
                                                                                                                  be from the yearly dredging by the
                                                             MR-1
       Figure 32: The                                         W.                                                  Corps of Engineers of Tillamook Bay
       progressive erosion
                                                                                                                  or the Columbia River. A more logical
       of Cape Lookout
       State ParkJollowing                                                                                        source would be from dredging sandy
       the 1982-83 EINifio.                                                                                       shoals in Netarts Bay in that this would
       (Upper) The
                                                                                                                  in effect return to the beach sand which
       destruction of the 109
       bulkhead and
                                                                                                                  had been swept into the bay, some of it
       initiation of dune
                                                                                                                  during the 1982-83 El Niflo. An associ-
       erosion during
       October 1984.                                                                                              ated positive effect would be the resto-
       (Lower) Erosion                                                                                            ration of the bay itself, which has
       during the winter of
       1988, leaving a beach                                                                                      undergone considerable shoaling.
       colnposed of cobbles                                                                                       However, Netarts Bay contains many
       and gravel rather
                                                                                                                  acres of protected wetlands and has the
       than sand, and the I-                                                        I.W,
       beams of the log                                                                                           highest diversity of clam species of any
       bulkhead at
                                                                                                                  Oregon estuary. Accordingly, dredging
       midbeach. (From
       Komar et al. [1988])                                                                                       and sand removal would have to be
                                                                                                                  balanced against the probable negative
                                                                                                                  impacts of such operations in the bay.







                                 64






                             Processes and Patterns of Sea-Cliff                                                             structure, including bedding stratification
                             Erosion                                                                                         i(horizontal or dipping) and the presence of joints
                                                                                                                             and faults. These factors are important in deter-
                                  The erosion of sea cliffs is a significant pro-                                            mining whether the cliff retreat takes the form of
                             blem along many of the world's coastlines,                                                      abrupt large-scale landsliding or the more contin-
                             including those of Oregon (figure 33). Most com-                                                uous failure of small portions of the cliff face.
                             muriities along the Oregon coast are built on up-                                               The processes of cliff attack are also complex.
                             lifted marine terraces or on alluvial slopes                                                    The retreat may be caused primarily by ground-
                             emanating from the nearby Coast Range. These                                                    water seepage and direct rain wash, with the
                             elevated lands are subject to erosion along their                                               ocean waves acting only to remove the accumu-
                             ocean margins with the formation of cliffs. State                                               lating talus at the base of the cliff. In other loca-
                             lands are also being lost as cliff erosion takes                                                tions the waves play a more active role, directly
                             place in coastal parks and affects state highways.                                              attacking the cliff and cutting away its base.
                                  Considering the extent and
                             importance of sea-cliff
                                                                                                6r,i
                             erosion, it is surprising how
                             few studies have focused on
                             this problem, at least in com-
                             parison with beach-erosion
                             problems and processes. Part                                                                                                                                                                     Figure 33: Sea cliff
                             of the reason for this is the                                                                                                                                                                    erosion in Lincoln

                                                                                                                                                                                                                              honws and recently
                             inherent difficulty in account-                                                                                                                                                                  City, threatening old
                             ing for the multitude of fac-                                                                                                                                                                    built condominium.
                             tors that can be involved in                                                                                                                                                             4
                             cliff erosion (figure 34). One
                             of the most problematic as-
                             pects is the cliff itself-its
                             material composition and its



                                                                                         OTHER FACTORS
                                                                                                I. rain wash on cliff face
                                                                                                2*gmund-water flow and pore pressures
                                                                                                3. vegetation cover
                                                                                                4. burrowing by rodents. etc.
                                                                                                5. people
                                                                                                     walking on cliff and talus
                                                                                                     carving graffiti on cliff face
                                                                                                     watering lawns
                                                                                                     cul"tts, etc.
                                                                                                     protective structures (sea wails. etc.)


                                                                                                                                                                                                                              Figure 34: Schentatic
                             OCEAN FACTORS                                                                                                                                                                                    diagrwn illustrating
                                  1. waves
                                          heights and periods (energy or energy flux)                                                                                                                                         the many factors and
                                          approach angle (longshore currents and littoral drift)                                                                                                                              processes involved in
                                          set-up and run-up                                                                                                   CLIFF FACTORS
                                  2. cell circulabon with rip currents                                                                                                                                                        sea-cliff erosion.
                                  3. tidal a iations                                                                                                               1. composition
                                  4. stor v ' rge                                                                                                                         "hardness" (e.g., compressive strength)
                                          rn su
                                  1. ea level (seasonal and long-term net changes)                                                                                        talus production
                                                                                                                                                                          source of beach sediments
                                                                                                                                                                   2. layering (bedding), joints, and faults
                                                                                                                                                                   3. inclination of rock layers
                                                                                                                                                                   4. height and slope of diff face







                                                   BEACH FACTORS
                                                        1. volume of beach sediments (buffering ability)
                                                        2. composition and grain size
                                                               control on beach morphology
                                                               sand 'blasting"
                                                        3. presence of drift  logs



                                                                                                                                                                                                                   65







                                Only limited study has been devoted specifi-         associated with ground-water seepage. Direct
                            cally to cliff erosion along the Oregon coast. The       wave attack of cliffs backing the beach has been
                            earliest work examined the occurrence of major           almost nonexistent, accounting for little or no
                            landslides and documented the importance of fac-         erosion. Yet the steepness of the cliff and its
                            tors such as rainfall intensity and   rockjointing       alongshore uniformity without appreciable
                            and bedding (Byme 1963, 1964;'North and Byrne            degradation by subaerial processes suggest that
                            1965). Little information is available on the long-      the cliff has experienced wave erosion in the not-
                            term erosion rates of sea cliffs not affected by         too-distant past. This condition is more evident at
                            major landslides. Stembridge (1975) compared             Bandon on the south coast, where, in addition to
                            two sequences of aerial photographs (1939 and            the steep cliff backing the beach, a number of
                            1971) to estimate erosion rates, but his analysis        stacks exist in the immediate offshore, many
                            was limited to only a few areas along the coast          having flat tops which continue the level of the
                            and yielded rough estimates of long-term                 marine terrace (Komar et a]. 1991). Our inter-
                            changes. In a more detailed study, but one limited       pretation of both the Cannon Beach and Bandon
                            to Lincoln County, Smith (1978) also used aerial         areas is that cliff erosion was initiated following
                            photographs to document average cliff erosion            the last major subduction earthquake 300 years
                            rates. Both studies revealed a considerable degree       ago, an event that likely resulted in the abrupt
                            of spatial variability along even short distances of     subsidence of those areas. However, the subse-
                            the coast. They also recognized the episodic na-         quent aseismic uplift has progressively dimin-
                            ture of the cliff erosion processes.                     ished the cliff erosion, to the point where it has
                               Our on-going Sea Grant research focuses on            essentially ceased at Cannon Beach and Bandon.
                            the patterns and processes of cliff erosion along        The central coast around Lincoln City likely also
                            the Oregon coast. This woik has examined the             experienced subsidence followed by uplift, but its
                            tectonic controls on the spatial variability of cliff    rates of uplift have been insufficient relative to
                            erosion along the full length of the coast, beach-       rising sea level to halt continued cliff erosion.
                            process factors in cliff retreat within more limited        Such tectonic/sea-level controls of cliff erosion
                            stretches of shore, erosiorxhnanagement issues at        along the Oregon coast can be viewed as a first-
                            specific locations, and the impacts of engineering       order pattern or trend. Superimposed on this
                            structures (Komar and McDougal 1988; Komar               coastwide vatiability are mom local processes
                            et al. 199 1; Komar and Shih 199 1; Sayre and            that can be viewed as second-order factors. Most
                            Komar 1988; Shih, in prep.). Our research has            important is the size of the beach, as this governs
                            confirmed that sea-cliff erosion is higl-dy variable     the ability of the beach to act as a buffer between
                            along the Oregon coast, but suggests that the            the sea cliffs and the eroding processes of waves
                            patterns are systematic and depend in part on the        and nearshore currents. The width and elevation
                            tectonic uplift versus global sea-level rise estab-      of the beaches vary from one littoral cell to an-
                            lished in figure 4. The north-central portion of the     other, each littoral cell consisting of a stretch of
                            coast, including the areas of Newport and Lincoln        beach isolated by rocky headlands. For example,
                            City, are experiencing some relative sea-level           the beach extending north from Yaquina Head to
                            rise, while further north toward Cannon Beach            Otter Rock and Cape Foulweather, the Beverly
                            and south of Coos Bay the tectonic uplift has            Beach littoral cell, does not offer adequate buffer
                            exceeded the rate of sea-level rise, at least within     protection, and as a result the sea cliffs backing
                            historic times. There is a rough first-order parallel    this beach have undergone significant retreat
                            between the extent of cliff erosion and relative         (though still at low rates when compared with
                            sea-level changes, with greater amounts of ero-          other coastlines). Its limited buffering capacity is
                            sion occurring in the Lincoln City area of the           evident in our ongoing measurements of wave
                            central coast (Komar and Shih 1991). Of parti-           run-up (Shih, in prep.). The objective is to
                            cular interest is the minimal erosion within             document the frequency with which waves reach
                            historic times of sea cliffs in the Cannon Beach         the talus and base of the sea cliff, and the inten-
                            and Bandon areas. What little cliff retreat exists is    sity of the swash run-up when it does so.


                            66







                Video-analysis techriiques are being employed to         to document the beach morphologies and how
                record the run-up. The measurements have estab-          they change with sediment sizes (Shih, in prep.).
                lished that the swash of waves frequently reaches        In addition, high-density profiling has been un-
                the cliff base in the Beverly Beach cell, but rarely     dertaken at approximately monthly intervals for
                in the other cells. Beach surveys show that this is      over a year at Gleneden Beach State Park (a re-
                due to the low elevations of the beach profile with      flective beach) and at the 21st Street beach access
                respect to mean sea level and high-tide elevations.      at the north end of Lincoln City (a dissipative
                   Of particular interest in our study of sea-cliff      beach). This high-density profiling permits the
                erosion has been the littoral cell containing Lin-       generation of detailed topographic maps of the
                coln City and Gleneden Beach, extending north            beach and more accurate analyses of seasonal
                from Govemment Point (Depoe Bay) to Cascade              changes. Of particular interest in this series of
                Head. The extensive development along this               profiles is the contrast in responses of the reflec-
                stretch of coast has given rise to a host of man-        tive and dissipative beaches to winter storms. The
                agement problems (figure 33). In addition, an            results document that profile changes and accom-
                unusual feature, marked longshore variations in          panying quantities of cross-shore sediment trans-
                the coarseness of the beach sands, produces long-        port are much greater on the coarse-grained
                shore changes in the beach morphology and                reflective beach (Gleneden Beach) than on the
                nearshore processes that are important to cliff          finer-grained dissipative beach at the north end of
                erosion. We have completed a detailed study of           the littoral cell. The rates of change as well as to-
                the changing grain-size distributions from beach-        tal quantities of sand moved under a given storm
                sand samples collected along the ftill length of         are larger on the steep reflective beach. This
                this cell (Shih, in prep.). Our analyses show that       makes the reflective beach a weaker buffer from
                the longshore variations in grain sizes are pro-         wave attack, and cliff erosion is therefore more
                duced by the relative proportions of discrete            active than in the area where the cliff is fronted
                grain-size modes within the overall sand-size dis-       by a fine-grained dissipative beach. In addition,
                tributions. We have succeeded in tracing these           we have found that the development of rip-
                individual modes to specific areas of the eroding        current embayments is extremely important on
                sea cliffs. Of interest are how these grain-sized        the reflective beach. These embayments largely
                modes move and mix alongshore and why the                control the locations of maximum episodic cliff
                mixing processes of the nearshore have not suc-          erosion (figure 35). The process is similar to that
                ceeded in homogenizing the beach sands to elim-          described earlier for the erosion of Siletz Spit,
                inate longshore variations. However, the overall         immediately north of Gleneden Beach, which is
                effect of this longshore sorting is that the beaches     also fronted by a reflective beach (figure 21).
                toward the central to south part of the cell are         Ground observations and aerial photographs
                coarsest; this includes the beaches fronting Siletz      show that rip currents on steep reflective beaches
                Spit and the community of Gleneden Beach.                tend to cut narrow, deep embayments, and so
                Sand sizes decrease somewhat toward the south,           they exert a significant role in controlling the im-
                but particularly toward the north where the sand         pact of erosion along the sand spit and also in the
                is finest in the Roads End area of Lincoln City.         the sea-cliff areas. In contrast, rip-current embay-
                The effects on the beach morphology are signi-           ments on the dissipative beaches of north Lincoln
                ficant, with the coarse-grained beach at Gleneden        City and elsewhere on the coast are broader in
                being a steep "reflective" beach for most of the         their longshore extents but do not cut as deeply
                year while the beach at Roads End has a low              through the beach berm.
                slope and is highly "dissipative" of the waves as           Bluff retreat in north Lincoln City, where the
                they cross the wide surf zone.                           dissipative beach is present, depends mainly on
                   Beach profiles have been obtained at eleven           subaerial processes of rainfall against the cliff
                stations spaced at roughly even intervals along          face and groundwater seepage. People have also
                the length of the Lincoln City littoral cell in order    had a significant impact; in some places their




                                                                                                                              67







                               carving graffiti on the cliff face is the dominant            the case where Tertiary marine formations are
                               factor in bluff retreat (figure 36). The loosened             included in the sea cliff (figure 2), since their
                               material accumulates as talus at the base of the              muddy consistency makes them especially sus-
                               cliff. That accumulation can continue for several             ceptible to sliding. Furthermore, it has been esti-
                               years, at which time it is removed by wave action             mated that these units dip seaward along more
                               during an unusually severe storm accompanied                  than half of the northern Oregon coast (Byrne
                               by extreme tide levels. There is little direct wave           1964; North and Byrne 1965), a geometry which
                               attack of the cliff and no evidence for undercut-             also contributes to their instability. In some cases
                               ting. However, once the talus has been removed                this instability results in the slow mass movement
                               by waves, sloughing of the cliff surface acceler-             of the cliff material toward the sea, amounting to
                               ates so that a new mass of talus quickly forms.               only a few 10s of centimeters a year. Although
                                  Landsliding has been a problem at some loca-               slow, it thoroughly disrupts the land mass and
                               tions along the Oregon coast. This is particularly            any attempts to place developments on the site
                                                                                                       (figure 37). Other landsliding involves
                                                                                                       the whole-scale movement of large
                                                                                                       masses at more rapid rates. Best known is
                                                      @F 7
                                                                                                       the infamous Jump-Off Joe area of New-
                                                                                                       port. In 1942 a large landslide developed
                                                                                                       in the bluff, figure 38, carrying more than
                                                                                                       a dozen homes to their destruction (Sayre
                                                                                                       and Komar 1988). In spite of continued
                                                                                                       stumping, in 1982 a condominium was
      Figure 35: Cliff                                                                                 built on a small remnant of bluff adjacent
                                                                                                       to
      erosion in Gleneden                                                                                 the major slide. Within three years,
                                               pc
                                                               M
      Beach due to a
      pronounced rip-                                                                                  slope retreat had caused the foundation to
      current embayment                                                                                fail (figuie 39), and the unfinished struc-
      that permitted the
                                                                                                       ture had to be destroyed by the city.
      swash of storm waves
      to reach the cliff base.
                                                                                                       Summary
                                                                                                          The Oregon coast is renowned for the
                                                                                                       intensity of its wave conditions. Winter
                                                4-
                                                                                                       storms commonly generate individual
                                                                                                       waves 40 to 50 feet high. The record is
                               XIT
                                                                                                       95 feet. Such storm waves deliver a tre-
                                                                                                       mendous; amount of energy to our coast,
                                                                                                       cutting back beaches and attacking
                                                                                                       coastal properties. They are assisted by
                                                                                                       rip currents that locally erode
                                                                                                       embayments into the beach, as well as
                                                                                                       tides and other processes that elevate wa-
                                                                                                       ter levels in the nearshore. In addition to
                                                                                                       these natural processes, people have
      Figure 36: The retreat
      of the bluff   incoln                                            N
                 inL
      City caused by
                                                                                                       contributed to the erosion, ranging from
      children carving
      graffiti and digging                                                                             children's carving their names on the
      caves.
                                                                                                       face of sea cliffs to the Corps of Engi-
                                                      0                                                neers' constructing a jetty at the inlet to
                                                                                                       Tillamook Bay.
                                                                                               "A
                                                                                                          The Oregon coast has had its share of
                                                                                                       erosion problems. Most dramatic has

                               68












                                                                                  Figure 37: The
                                                                                  destruction of streets
                                                                                  and sewers by
                                                                                  landsliding within a
                                                                                  new development
                                                                                  north of Yaquina
                                                                                  Head.





















                                                                                  Figure 38: The 194243 landslide
                                                                                  at Jump-OffJoe, Newport, showing
                                                 "low
                                                                                  the initial destruction of homes.
                                                                                  The aerial photo datesfrom 1961.
                                                                                  (Pholosfrom Lincoln County
                                                                                  Historical Society, Newport)








                                                                  N"








                                                                                                                                Figure 39: The
                                                                                                                                construction (far left)
                                                                                                                                and destruction (left)
                                                                                                                                Of the condominium
                                                                                                                                built in 1982 on a
                                                                                                                                small remnant of
                                                                                                                                marine terrace at
                                                                                                                                Jump-OffJoe. (From
                                                                                                                                Sayre and Komar
                                                                                                                                119881)






                                                                                              z"




                                                                                                                              69






                             been the impact on sand spits; seveiW case               exceed the tectonic rise and bring about more ex-
                             studies have been summarized in this chapter.            tensive erosion. Although the impact would be
                             Though less dramatic, the cumulative erosion of          smaller and come later than it would along the
                             sea cliffs has affected a number of coastal com-         low-relief and subsiding coastal states, it is im-
                             munifies as well as parklands and highways.              portant that potential increases in sea level enter
                             However, the Oregon coast has actually suffered          into management considerations for the Oregon
                             relatively few erosional impacts leading to major        coast. More ominous is the possibility that an ex-
                             property losses, at least in comparison with most        treme earthquake will occur on the Northwest
                             other coastal states. This is in part due to its phys-   coast. In addition to the immediate impacts of the
                             ical setting. The coast consists of a series of          ground shaking and the generation of a tsunami,
                             pocket beaches or littoral cells separated by rocky      the abrupt subsidence of portions of the coast will
                             headlands or more extensive stretches of rocky           "bate extensive erosion in areas that have not
                             shore. In each cell there is a seasonal reversal in      suffered from wave attack within historic times.
                             the direction of longshoree sand transport, but with     The implications of this scenario for coastal plan-
                             a long-term net drift that is essentially zero. As a     ning are staggering, yet the decisions officials
                             result, when jetties have been constructed on the        must make are not simple ones. As discussed
                             Oregon coast, they cause only a local rearrange-         above, it has been estimated that catastrophic
                             ment of beach sands and adjustments of the               earthquakes and land-level changes have oc-
                             shorelines, with no lasting major impacts (the one       curred at least six times in the past 4,000 years, at
                             exception was Bayocean Spit, where erosion was           intervals ranging from 300 to 1,000 years. The
                             due to the construction of one jetty rather than         last recorded event took place about 300 years
                             two). This contrasts with most U.S. shorelines,          ago, so we are clearly in the window of potential
                             where jetty and breakwater construction has              for another event. At some stage, and preferably
                             blocked a net littoral drift and severely eroded the     sooner than later, coastal management decisions
                             downdrift beaches and communities.                       need to be made reflecting this potentially ex-
                               The tectonic setting of the Oregon coast is also       treme hazard. In the meantime, we have to reflect
                             important in limiting its erosion. Most significant      on the wisdom of developing low-lying areas and
                             is the tectonic uplift that currently exceeds the        the edges of ocean cliffs along the coast.
                             global rise in sea level over much of the coast,           We have made numerous mistakes in develop-
                             while minimizing the transgression of the sea in         ing the Oregon coast that have placed homes and
                             other areas. Unlike the east and Gulf coasts of the      condominiums in the path of erosion. Develop-
                             U.S., where the transgression has resulted in sub-       ment has been permitted in the foredunes of sand
                             stantial landward migrations of the shoreline and        spits immediately backing the beach, along the
                             property losses, erosion of Oregon's sandy shores        edges of precipitous sea cliffs, and even in the
                             is cyclical, with minimal net loss. This was first       area of the active Jump-Off Joe landslide. Such
                             noted on Siletz Spit, where an episode of erosion        unwise developments and the accompanying pro-
                             cutting into the foredunes was followed by a de-         liferation of seawalls and riprap revetments has
                             cade of accretion so that the dunes built back out       progressively degraded the qualifies we cherish in
                             to their former extent. An extreme example was           the Oregon coast.
                             noted on Nestucca Spit, where an extensive
                             mound of riprap placed during erosion in 1978 is         Acknowledgments
                             now covered by dune sands that are blowing in-
                             land, inundating houses. Similarly, the tectonic           This review was funded by a grant from the
                             uplift has resulted in low rates of cliff recession,     National Oceanic and Atmospheric Administra-
                             much smaller than those documented in other              tion, Office of Sea Grant (grant NA89AA-D-
                             coastal areas.                                           SG108, project R/CM-36). The views expressed
                               This situation may change in the future. There         are those of the author and do not necessarily
                             is the potential for accelerated rates of sea-level      reflect the views of NOAA or any of its sub-
                             rise caused by greenhouse warming that could             agencies. I would like to thank Jim Good, Kevin


                             70







               Tillitson, Shuyer-Ming Shih, and Mark Lorang        Enfield, D.B., and Allen, J.S., 1980, On the
               for their helpful comments in reviewing this           structure and dynamics of monthly mean sea
               paper.                                                 level anomalies along the Pacific coast of
                                                                      North and South America: Journal of Physi-
                                                                      cal Oceanography 10:557-578.
               References                                          Hicks, S.D., 1972, On the classification and
               Aguilar-Tunon, N.A., and Komar, P.D., 1978,            trends of long period sea level series: Shore
                  The annual cycle of profile changes of two          and Beach 40:20-23.
                  Oregon beaches: The Ore Bin 40:25-39.            Hicks, S.D., Debaugh, H.A., and Hickman,
               Atwater, B.F., 1987, Evidence for great Holo-          L.E., 1983, Sea level variations for the
                  cene earthquakes along the outer coast of           United States, 1855-1980: U.S. Dept. of
                  Washington state: Science 236:942-944.              Commerce, NOAA, National Ocean Service,
               Atwater, B.F., and Yamaguchi, D.K., 1991,              Rockville, MD.
                  Sudden, probably coseismic subsidence of         Huyer, A., Gilbert, W.E., and Pittock, H.L.,
                  Holocene trees and grass in coastal Wash-           1983, Anomalous sea levels at Newport,
                  ington State: Geology 9:706-709.                    Oregon, during the 1982-83 El Nifio: Coastal
               Boggs, S., 1969, Distribution of heavy minerals        Oceanography and Climatology News 5:37-
                  in the Sixes River, Curry County, Oregon:           39.
                  The Ore Bin 31:133-150.                          Komar, P.D., 1976, Beach Processes and
               Boggs, W.S., and Jones, C.A., 1976, Seasonal           Sedimentation: Prentice-Hall, Inc.,
                  reversal of flood-tide dominated sediment           Englewood Cliffs, New Jersey.
                  transport in a small Oregon estuary: Geo-        Komar, P.D., 1978, Wave conditions on the
                  logical Society of America Bulletin 87:419-         Oregon coast during the winter of 1977-1978
                  426.                                                and the resulting erosion of Nestucca Spit:
               Byrne, J.V., 1963, Coastal erosion, northern           Shore and Beach 46:3-8.
                  Oregon: in Essays in Marine Geology in           Komar, P.D., 1983a, The erosion of Siletz Spit,
                  Honor of K.O. Emery, Univ. of Southern              Oregon: in Handbook of Coastal Processes
                  California Press, Los Angeles, California, p.       and Erosion, CRC Press, Boca Raton,
                  11-33.                                              Florida, p. 65-76.
               Byrrie, J.V., 1964, An erosional classification     Komar, P.D., 1983b, Coastal erosion in re-
                  for the northern Oregon coast: Assoc. of            sponse to the construction of jetties and
                  American Geographers Annals 54:329-335.             breakwaters: in Handbook of Coastal
               Clemens, K.E., and Komar, P.D., 1988a                  Processes and Erosion, CRC Press, Boca
                                                                      Raton, Florida, p. 191-204.
                  Oregon beach-sand compositions produced
                  by the mixing of sediments under a trans-        Komar, P.D., 1985, Oregon: in The World's
                  gressing sea: Journal of Sedimentary Petrol-        Coastline, E.C. Bird and M.L. Schwartz
                  ogy 58:519-529.                                     (eds.), Van Nostrand Reinhold Co., New
               Clemens, K.E., and Komar, P.D., 1988b,                 York, p. 23-26.
                  Tracers of sand movement on the Oregon           Komar, P.D., 1986, The 1982-83 El Niflo and
                  coast: Proceeding 2 1 st Coastal Engr. Conf.,       erosion on the coast of Oregon: Shore and
                  Amer. Society Civil Engrs., p. 1338-135 1.          Beach 54:3-12.
               Creech, C., 198 1, Nearshore wave climatology,      Komar, P.D., and Rea, C.C., 1976, Erosion of
                  Yaquina Bay, Oregon (1971-1981): Oregon             Siletz Spit, Oregon: Shore and Beach 44:
                  State Univ. Sea Grant Program, Report               9-15.
                  ORESU-T-81-002.                                  Komar, P.D., and Terich, T.A., 1976, Changes
               Darienzo, M.E., and Peterson, C.D., 1990,              due to jetties at Tillamook Bay, Oregon,
                  Episodic tectonic subsidence of late Holo-          Proceedings 15th Coastal Engr. Conf., Amer.
                  cene salt marshes, northern Oregon central          Soc. Civil Engrs., p. 1791-1811.
                  Cascadia margin: Tectonics 9:1-22.



                                                                                                                   71







                           Komar, P.D., Quinn, W., Creech, C., Rea, C.C.,     National Research Council, 1987, Responding
                             and Lizarraga-Arciniega, J.R., 1976a, Wave          to changes in sea level: Engineering implica-
                             conditions and beach erosion on the Oregon          tions. Washington, D.C., National Academy
                             coast: The Ore Bin 38:103-112.                      Press.
                           Komar, P.D., Lizarraga-Arciniega, J.R., and        North, W.B., and Byrne, J.V., 1965, Coastal
                             Terich, T.A., 1976b, Oregon coast shoreline         landslides in northern Oregon: The Ore Bin
                             changes due to jetties: Jour. Waterways,            27:217-241.
                             Harbors and Coastal Engr., Amer. Society         Peterson, C., Scheidegger, K.F., and Komar,
                             Civil Engrs. 102(WWI): 13-30.                       P.D., 1982, Sand-dispersal patterns in an
                           Komar, P.D., and McKinney, B.A., 1977, The            active-margin estuary of the northwestern
                             spring 1976 erosion of Siletz Spit, Oregon,         United States as indicated by sand composi-
                             with an analysis of the causative storm             tion, texture and bedforms: Marine Geology
                             conditions: Shore and Beach 45:23-30.               50:77-96.
                           Komar, P.D., and McDougal, W.G., 1988,             Peterson, C.D., Scheidegger, K.F., and
                             Coastal erosion and engineering structures:         Schrader, H.J. 1984a, Holocene depositional
                             The Oregon experience: Journal of Coastal           evolution of a small active-margin estuary of
                             Research 4:77-92.                                   the northwestern United States: Marine
                           Komar, P.D., Good, J.W., and Shih, S.-M.,             Geology 59:51-83.
                             1988, Erosion of Netarts Spit, Oregon:           Peterson, C., Scheidegger, K.F., Komar, P.D.,
                             Continued impacts of the 1982-83 El Nifio:          and Niem, W., 1984b, Sediment composition
                             Shore and Beach 57:11-19.                           and hydrography in six high-gradient
                           Komar, P.D., and Good, J.W., 1989, Long-term          estuaries of the northwestern United States:
                             erosion impacts of the 1982-83 El Nifio on          Journal of Sedimentary Petrology 54:86-97.
                             the Oregon coast: Coastal Zone '89: Amer.        Phipps, J.B., and Smith, J.M., 1978, Coastal
                             Society Civil Engrs., p. 3785-3794.                 accretion and erosion in southwest Washing-
                           Komar, P.D., Torstenson, R.W., and Shih, S.-          ton: Department of Ecology, State of Wash-
                             M., 1991, Bandon, Oregon: Coastal develop-          ington, Olympia.
                             ment and the potential for extreme ocean         Rogers, L.C., 1966, Blue Water 2 lives up to
                             hazards: Shore and Beach 59:14-22.                  promise: Oil and Gas Journal, Aug. 15, p.
                           Komar, P.D., and Shih, S.-M., 1991, Sea-cliff         73-75.
                             erosion along the Oregon coast, Coastal          Sayre, W.O., and Komar, P.D., 1988, The
                             Sediments '91, Amer. Society Civil Engrs.,          Jump-Off Joe landslide at Newport, Oregon:
                             p. 1558-1570.                                       History of erosion, development and destruc-
                           Kulm, L.D., and Byrne, J.V., 1966, Sedimen-           tion: Shore and Beach 52:15-22.
                             tary response to hydrography in an Oregon        Shih, S.-M., in prep. Ph.D. thesis, Oregon State
                             estuary: Marine Geology 4:85-118.                   University, Corvallis, Oregon.
                           McKinney, B.A., 1977, The Spring 1976              Scheidegger, K.F., Kulm, L.D., and Runge,
                             erosion of Siletz Spit, Oregon, with an             E.J., 197 1, Sediment sources and dispersal
                             analysis of the causative wave and tide             patterns of Oregon continental shelf sands:
                             conditions: Master of Science Thesis,               Journal of Sedimentary Petrology 41:1112-
                             Oregon State University.                            1120.
                           Mitchell, C.E., Weldon, R.J., Vincent, R, and      Scheidegger, K.F., and Phipps, J.P., 1976,
                             Pittock, H.L., 1991, Active uplift of the           Dispersal patterns of sand in Grays Harbor
                             Pacific Northwest margin (abstract): EOS,           estuary, Washington: Journal of Sedimentary
                             the American Geophysical Union.                     Petrology 46:163-166.
                           National Research Council, 1983, Changing          Smith, E.C., 1978, Determination of coastal
                             climate: Report of the carbon dioxide               changes in Lincoln County, Oregon, using
                             assessment committee: Washington, D.C.,             aerial photographic interpretation: Research
                             National Academy Press.                             Paper, Dept. of Geography, Oregon State
                                                                                 Univ., Corvallis.



                           72







              Stembridge, J.E., 1975, Shoreline changes and     Wyrtki, K., 1984, The slope of sea level along
                physiographic hazards on the Oregon coast:         the equator during the 1982/1983 El Niflo:
                Ph.D. dissertation, Dept. of Geography,            Journal of Geophysical Research 89:10,419-
                Univ. of Oregon, Eugene.                           24.
              Terich, T.A., and Komar, P.D., 1974, Bayocean Zopf, D.O., Creech, H.C., and Quirm, W.H.,
                Spit, Oregon: History of development and ero-      1976, The wavemeter: A land-based system
                sional destruction: Shore and Beach 42:3- 10.      for measuring nearshore ocean waves: NITS
              Vincent, P., 1989, Geodetic deformation of the       Journal 10: 19-25.
                Oregon Cascadia Margin: M.S. dissertation,
                Univ. of Oregon, Eugene.
              Watts, J.S., and Faulkner, R.E., 1968, Design-
                ing a drilling rig for severe seas: Ocean
                Industry 3:28-37.













































                                                                                                             73






            WENCE             COMMENTS ON PAUL KOMAR'S "COASTAL
                              ZONE PROCESSES AND HAZARDS"

            0                 John Beaulieu
                              Oregon Department of Geology and Mineral Industries


       COASTAL
       PROCESSES AND                                                                  to be applied in all cases, regardless of specific
       HAZARDS                Introduction                                            circumstances. The questions in my mind as I
                              The Oregon Department of Geology and Mineral            read Komar's paper were, where did we go
                              Industries is involved in diverse activities in the     wrong, and does the paper help us find a
                              Oregon coastal zone. They include participating         new direction?
                              in the Oregon Policy Advisory Commission;
                              regulating oil, gas, and geothermal exploration
                              and drilling from a technical standpoint; sponsor-      Nine Standards of Decision Making
                              ing the Exclusive Economic Zone Data Need                  When I look at coastal decision making, I ap-
                              Symposium held in the fall of 1991; and collect-        ply nine standards.
                              ing routine data. In the 1970s, the department in-
                              vestigated geologic hazards in all coastal Oregon       1. Facts vs. Preference
                              counties. Its investigation included some consid-          When dealing with a coastal issue, are we
                              eration of coastal processes.                           placing facts on the table, or are we trying to ra-
                                 As a result of these various activities, the         tionalize a personal preference? Looking at
                              agency has developed an admittedly incomplete,          Komar's paper, I see good factual discussions of
                              yet useful, knowledge of some of the coastal haz-       pocket beaches, sea level trends, the seasonality
                              ards that Omgoi@iians must deal with. The topical       of processes, currents, grain size, and so on. His
                              information, field data, geological perspectives,       paper provides the conceptual framework that can
                              and even personal opinions that sometimes get           lead to factual and objective analysis of situations
                              stiffed around yield occasional insights of value       where decisions must be made. I don't believe I
                              to people grappling with coastal issues.                read the words "in my opinioif'anywhere in
                                 In spite of all the good work that is going on at    the text.
                              the coast, there is a disturbing pattern that we ob-    2. Inventories vs. Anecdotes.
                              serve from time to time. I would like to describe          in making a policy decision that affects one
                              that pattern to you and then suggest nine possible      area, it is easy to turn to another area that superfi-
                              ways it can be avoided. As I do this, I will com-       cially seems the same and then to conclude that
                              ment on Paul Komar's paper.                             the first area in question should be treated the
                                 It was during the 1970s that Oregon became           same as the second. We don't need anecdotes; we
                              enlightened in regard to hazards in the coastal         need inventories of facts to help us make deci-
                              zone. It was then that coastal studies began, the       sions. The Komar paper provides us with a num-
                              Marine Science Center was built, and state gov-         ber of good parameters for developing such
                              emment began to put into place goals for dealing        inventories. Although Komar gives examples
                              with coastal problems. In one flash of brilliance,      here and them to clarify a point, he makes no ar-
                              for example, the concept of the foredune was de-        gument by anecdote.
                              veloped. It became the cornerstone of the coastal
                              goal. We learned that a foredune in a given loca-       3. New Concepts vs. Personal Experience
                              tion was unstable and therefore that such instabil-        it is common in coastal studies to hear people
                              ity must be considered in future development.           stretch their personal knowledge beyond its appli-
                                 Over the years some of us have seen these            cation to arrive at conclusions that may not be
                              sparks of enlightenment slowly fade to dull, but        appropriate. We need individuals who seek out
                              everlasting, embers. I'licy have become dogmas          and use emerging concepts and technologies with

                            74







                 which they are not initially familiar. In Komar's        Komar provides distinct conclusions and prin-
                 work, we see inforination on subduction zone             ciples relating to grain size, grain composition,
                 earthquakes. These and other concepts are fairly         and other quantitative measurements. With this
                 new to the scene and we need to learn more               kind of approach, we can make better decisions.
                 about them.                                              7. No Risk vs; Acceptable Risk
                 4. Perspective vs. Emotion                                  How much risk is acceptable to society?
                   When a problem is identified on the coast, it is       Looking at the east coast of North America, we
                 very easy for us to react emotionally, not because       see that a risk of hurricanes every 10 years or so
                 the situation truly justifies such a response, but       is considered acceptable. Building continues with
                 because we have a strong personal stake in the           proper insurance and evacuation plans. Here on
                 outcome. Facts allow us to put the problem into          the West Coast we may have different standards
                 perspective. The Komar paper proceeds from               of what is acceptable and what is not. To prop-
                 factual discussions and provides the basis for per-      erly implement a coastal hazard policy, we must
                 spective. Just one example will suffice. Quite of-       identify the level of acceptable risk. It may not be
                 ten when we read about coastal erosion, we are           enough to simply say that over some time frame
                 told about the loss of sand and cliff but not about      we may incur some kind of risk.
                 the rebuilding that may follow. Yet hem in Or-           8. No Rules of Thumb
                 egon, where the coastline basically is held up by           A strictly geographic approach is primarily
                 headlands, cycles of erosion are commonly fol-           descriptive and tends to clarify and categorize
                 lowed by rebuilding. In such cases, focusing only        coastal features. Variables in the Oregon coastal
                 on the erosion would be very misleading. Komar           zone don't allow this approach as an end in itself.
                 gives us examples of both erosion and recon-             Winter waves are not the same as summer waves.
                 struction. This provides us with a fuller picture of     Sand reservoirs come and go. Migrating sand
                 the hazards we are dealing with.                         gets around some headlands but not others. What
                 5. Reasons vs. the Real Reasons                          we think we see on the Oregon coast isn't neces-
                    We are often given many reasons why a par-            sarily what we get. No two beaches are exactly
                 ticular development or proposition either can or         the same at any given time. Further, no beach is
                 cannot proceed. The arguments may sound good             the same through time because now we hear, for
                 to the uninitiated, but to persons well versed in        example, that the land rises and falls with seismic
                 the subject they ring hollow. The question is,           events and interseismic deformation, respec-
                 what are the real reasons for making a decision?         tively-or the opposite, depending on where you
                 One key to more accurately identifying real rea-         are. Or the sea rises and falls with El Nifio.
                 sons is to use a multidisciplinary approach in           9. Implementation Strategy vs. Conflict
                 which various factors can be played against each         Management
                 other to arrive at the best conclusion. Komar ad-           Once we have collected all the facts and de-
                 dresses many of the major factors at play along          fined acceptable risks, we still need a strategy for
                 the Oregon coast and therefore provides a basis          implementing decisions. Looking at various ex-
                 for identifying real reasons for making decisions.       amples along the Oregon coast, such as Rogue
                 6. Analyses vs. Analogies                                Shores, Breakers Point, and Alsea Spit, we see a
                    People who discuss coastal problems often do          little too much conflict and not enough faith in
                 so using analogies that may or may not apply.            conflict resolution or decision making.
                 What is needed is more factual data with which              Oregon has been deficient in translating data
                 to make sound decisions. Komar gives us ex-              to acceptable policies. Through hit or miss tac-
                 amples, interpretations, and discussions, which          tics, we register geologists, we discuss the forinat
                 by their nature identify the types of analyses that      and the contents of reports, and sometimes we
                 can give us good answers. Whereas many con-              play with the idea of circuit riders, or experts,
                 clusions about the coast begin with, "Everybody          who can go around and help out. Other states are
                 knows" or "I know of another beach where. . .            more focused. Oregon cities and counties need to


                                                                                                                               75







                             settle upon strategies for translating data into        dards implied reliance on facts, appreciation for
                             policy decisions.                                       variability, judgments of risk, and strategies for
                                I began by saying that them were certain stan-       implementation. With these standards in mind,
                             dards I applied to any decision making along the        Komar's paper should be required reading for
                             coastal zone. In the simplest of terms, these stan-     policyrnakers in the Oregon coastal zone.























































                            76

















































































                                                                                                                                                                                                                                                                                                                                      F4..


                                                                                                                                                                                                                                                                                                                                                                                        . . .. ..... . ..





                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 -AW;


                                                                                                                                                                                                                                                                                                                                                                                                                                                                   ::.A


                                                                                                                                                                                                                                                                                                           5
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                                                                                                                                                                                                                                                                                                              M
                                                                     ON rdlIN I )KI


                                                                                                                                                                                                                                                                                                                                                                                                                                            I...                       h






                SHORE PROTECTION AND ENGINEERING WITH                                                                             ENGINEERING
                SPECIAL REFERENCE TO THE OREGON COAST                                                                             ------       4-45

                Nicholas C. Kraus
                Coastal Engineering Research Center, Vicksburg, Mississippi

                William G. McDougal
                                                                                  y
                Department of Civil Engineering, Oregon State Universit                                                          SHORE
                                                                                                                                 PROTECTION
                                                                                                                                 AND
                                                                                                                                 ENGINEERING
                Introduction                                            mid- I 960s, these coasts had experienced devas-
                The need for engineering solutions to problems of       tating hurricanes and storms that greatly eroded
                                                                        beaches, inundated and breached barrier islands,
                chroriic coastal erosion was recognized nationally      and even created a major tidal inlet at Shinnecock
                in 1930 when the United States Congress autho-          Inlet, New York. Loss of beaches was com-
                rized formation of the Beach Erosion Board              pounded by several factors: natural depletion of
                (BEB) and designated the U.S. Army Corps of             coastal bluffs along the New Jersey coast; reten-
                Engineers as the Federal entity responsible for         tion of sand behind seawalls and revetments that
                shore protection. In 1954, the BEB published            would nonnally be released to the littoral system
                Technical Report Number 4 (TR4), entitled Shore         by the formerly eroding coastline they protected;
                Protection, Planning and Design (BEB 1954),             and stabilization of inlets with jetties that blocked
                with revised editions appearing in 1957, 196 1,         longshore movement of sand. These types of ero-
                and 1966. TR4 was a milestone publication that          sional events have occurred many times and at
                defined and consolidated the state of knowledge         many locations on the U.S. shoreline. The U.S.
                on shore protection. In 1963, Congressional ac-         Geological Survey (Williams et al. 199 1) esti-
                tion created the Coastal Engineering Research           mates that most of the coastline of the lower 48
                Center (CERC) to supersede the BEB, and TR4             states is experiencing moderate to severe erosion,
                was replaced by the more comprehensive Shore            The relative magnitude and distribution of this
                Protection Manual (SPM), issued by CERC in              coastal erosion is shown in figure 1, adapted from
                1973 and revised in 1984 (SPM 1984). The SPM            Williams et al. (199 1).
                serves as the authoritative reference on shore pro-        Examples of erosion in the Pacific Northwest
                tection and coastal sediment processes and is           are the short epochs that occurred in the winter of
                used as a text book and design manual around the        1977-1978, when four severe storms attacked the
                world. Recognizing many recent scientific devel-        Oregon coast, one during a Spring high fide that
                opments and advances in engineering practice in         caused breaching of Nestucca Spit (Komar 1978).
                the area of shore protection, CERC is planning a        Another epoch occurred in the winter of 1982-
                new publication tentatively called the Coastal          1983, when both high water levels and storm
                Engineering Manual (CEM) that will supersede            waves associated with El Niho (the [Christmas]
                the SPM and expand into other areas of coastal          Child) occurred. El Nifio is a large-scale climato-
                engineering. The CEM will incorporate recent            logical event that periodically originates off Peru
                advances in information processing to facilitate        around the Christmas season. El Nifio has been
                periodic transfer of technology to coastal engi-        associated with severe erosion and large-scale
                neering researchers and practitioners as advances       longshore translation of beach sediments (Komar
                are made in this rapidly developing field.              1986; Komar and Good 1989; Komar, Good, and
                   One of the first activities of the BEB was to        Shih 1989). All coasts experience adjustment of
                investigate severe erosion that was occurring           the shoreline through long-term, short-term, and
                along the northern New Jersey coast and the             cyclical erosion and accretion events; as a coast
                southern shore of Long Island, New York. In the         such as Oregon's is used more, these changes be-
                past and again in 1938 and in the mid-1950s to          come more apparent and of concern.

                                                                                                                             79
















                            Portland
                                                                                                                             Por1lon



                                                                                                                             ,..,an
                                                                                          La@ke    'ok"
                                                                                                   H.,@.           Buffalo Providence
                                                                                       Michigan            Lake
                                                                                      Milwaukee     a rot   Erie      New York
                                                                                         Chicago              Cleveland

                                                                                                               Washington

                      S n
                      Francisco

                                                                                                                     Norfolk



                                                                                                                Wilmington  iiilw
          P A C I F C       Los Angeles
                                                                                                                             A r L A N TC
           0 C E A N                                                                                         Charleston I
                              Son Diego                                                                               'r
                                                                                                                               0 C E A N


                                                                                                   Mobile Jacksonville4
                                                                                       New
                                                                                                           dft
                                                                                                           Savannah



                      ANNUAL SHORELINE                                    Houston       Orleans
                            CHANGE                                                                             I     Po
                        Severely eroding                                                    G U L F                 Miami
                 IBM Moderately eroding                                                  F  M E X /C 0
                        Relatively stable


         Figure 1. Coastal erosion around the continental United States (after Williams el al. 1991).



                              Erosion of the shore and beaches was first per-     relatively short pocket beaches terminated by
                            ceived on a regional scale in the vicinity of major   headlands that effectively block sand from mov-
                            coastal metropolitan areas relatively early in the    ing to adjacent compartments (for example,
                            century (the massive seawall built in the late        Komar 1991). Waves and wind, backshore and
                            1800s along the north New Jersey coast). Ero-         offshore topography, sediment supply, and rela-
                            sion and inundation are now becoming concerns         tive sea-level rise, among other factors, also vary
                            in other states as coastal property is developed or   between coasts and, indeed, along adjacent sec-
                            a desire exists to maintain natural beaches. Many     tions of coast.
                            states passed coastal zone management legisla-           Given the preceding as backdrop, it is clear
                            tion in the 1970s to regulate coastal usage. These    that a specific shore-protection design on one
                            policies are typically under active debate by com-    coast will probably not translate directly to an-
                            peting interests and undergo increasing scrutiny      other coast. Nevertheless, a body of knowledge
                            as both specialists and the public gain knowledge     exists on shore-protection methods. It is the in-
                            of the particular coast and better understand         tent of this paper to review these basic coastal
                            shore-protection measures.                            engineering approaches and tools; they are the
                              Although the basic physical processes govern-       orthodox and generally accepted procedures for
                            ing wave and current motion, sediment transport,      dealing with coastal erosion. In the paper, we re-
                            and beach change are the same on all coasts, their    view selected coastal sediment processes as
                            manifestation and the relative importance of indi-    background for the material on shore-protection
                            vidual components can be quite different, as can      methods. We then review some of the elements
                            be the geology and geomorphology of the coast.        of shore-protection planning to establish a frame-
                            For example, the east coast of Horida is typified     work for a more specific discussion of shore-pro-
                            by long stretches of sandy beaches terminated by      tection methods.
                            inlets, whereas the coast of Oregon is typified by


                            80







                    This paper is written from the perspective of             1. Plan regionally, engineer locally
                  functional design, a term expressing formulation               The functionality requirements and constraints
                  and evaluation of a project by the functioning or           (step 1) will usually encompass diverse space and
                  performance of the design plan. Only occasional             time scales, requiring comprehensive planning as
                  reference will be made to economics and con-                opposed to single-project planning. It is essential
                  struction details. Numerical simulation modeling            to embed the project in the regional processes of
                  is a useful tool in evaluating alternative designs          the coast, for example, over the littoral cell con-
                  and optimizing the final functional design. Al-             taining the project.
                  though we do not discuss modeling in detail, we                Example 1: A series of groins constructed by a
                  do give selected results and citations to the litera-       group of homeowners may protect their proper-
                  ture. A collection of papers on shoreline change            ties but trap sand and deprive downdrift property
                  and profile change modeling as currently per-               owners. The problem statement in such a situa-
                  formed at CERC can be found in Kraus (1990).                tion should include downdrift impacts, which
                                                                              may expand the region that should be considered,
                  Elements of Shore-Protection Planning                       as well as the local project area.
                                                                                 Example 2: If a relatively undeveloped coast is
                    In Us section we touch on key points in the               experiencing a tendency for long-term erosion,
                  process of planning, designing, and evaluating the          such as from subsidence or loss of sand supply, it
                  performance of a shore-protection project. All              may be best to rigorously enforce set-back lines
                  possible options should be available in the first           rather than attempt to hold the position of the
                  stage, or reconnaissance level, of planning in de-          shoreline with structures. These types of consid-
                  termining possible shore-protection solutions. At           erations typify the approach of planning region--
                  thefeasibility level of planning, which leads to            ally and engineering locally.
                  the final design through intensive study and com-
                  parison of alternative plans, an optimal plan is            2. Shore retention and shore protection
                  developed. Here the optimal plan is taken to be                Shore retention specifically refers to the main-
                  the shore-protection plan that accomplishes the             tenance of a beach, whereas shore protection in
                  design objectives for the least cost and in accor-          the present context means shore retention and
                  dance with management policies for the particu-             protection of the backland. More will be said
                  lar coast.                                                  about this below. In order to maintain a beach,
                    The aforementioned planning process for a                 one must explicitly include shore-retention con-
                  shore-protection project is summarized in the fol-          siderations in the shore-protection planning.
                  lowing steps modified from Kraus (1989):                    3. Compare alternatives objectively
                  1.  Identify the functionality requirements, iden-             It is wise to evaluate and compare alternative
                      tify constraints, and develop criteria forjudg-         shore-protection designs for their local and
                      ing the performance or objectives of the                regional functioning. For larger projects, num-
                      project.                                                erical simulation modeling is often conducted to
                  2.  Assemble and analyze relevant data.                     compare alternative designs. Each alternative is
                  3.  Determine project alternatives.                         thereby evaluated in the same way. Such results
                  4.  Select and optimize project design. (Return             are then interpreted through experience along the
                      to step 1, as necessary.)                               coast to determine the appropriate final plan.
                  5.  Construct the project.                                  After planners evaluate the alternatives, they
                  6.  Monitor and maintain the project (fine-tuning           modify their plans; and the objective of their
                      as necessary).                                          project may change somewhat as they learn more
                  7.  Evaluate the project according to criteria in           about the problem and its possible solutions (step
                      step 1, and report the results.                         4 to step 1).
                    The steps are more or less self-explanatory.              4. Be innovative
                  Here, an attempt is made to encapsulize the                    Most sites and projects have unique features
                  engineering planning process in five principles.            that make direct transfer of solutions from one

                                                                                                                                       81







                            coast to another infeasible. Although solutions of      breakwater, that create a "diffraction currenf 'by
                            a similar nature may be appropriate along the           decreasing wave height and directing waves and
                            same coastline, modification of the design will         the current into the shadow zone of the blocking
                            probably be required to suit the local conditions.      object. Wind also can produce substantial
                            The features of projects that perform well (as de-      longshore currents. Longshore transport is gener-
                            termined by following steps 6 and 7) can be             ally most intense in the surf zone, where wave
                            adopted and modified as necessary to suit condi-        breaking is active and greatly decreases in magni-
                            tions at the new site. In the process of evaluating     tude with distance seaward from the surf zone.
                            alternatives, engineers may develop new or supe-        Because longshore currents are persistent, long-
                            rior designs that had not previously been consid-       term change in the beach planform is almost al-
                            ered as options.                                        ways related to the longshore current and
                            5. Fine-tune                                            associated longshore sediment transport.
                              Monitoring a project (step 6) allows us to un-           Longshore transport on a coast is often de-
                            derstand its performance and maintain the re-           scribed in terms of the net and gross rates of
                            quired level and longevity of protection. It may        transport. An observer standing on the coast can
                            be necessary to fine-tune the design, and it Is         distinguish the transport along the coast by the
                            common to put a project in place at minimal cost        sand moving to the right or left, both quantities
                            for the level of protection and build in triggers to    considered as being positive. The net transport
                            signal that some action should be taken. For ex-        rate is then the right-moving transport minus the
                                                                                    left-moving transport. Some authors include the
                            ample, the replenishment schedule for a feeder          sign (if the right-moving is greater than the left-
                            beach (a sacrificial beach fill that is expected to  .  moving transport, the net is to the right and posi-
                            erode and nourish downdrift beaches) may be ini-        tive; if the left-moving is greater than the
                            tially set at the longest estimated acceptable time     right-moving transport, the net is to the left and
                            interval with the contingency to replenish it more      negative). Other authors define the net as the
                            frequently according to some criterion established
                            at downdrift shores.                                    magrutude of the difference (always positive).
                                                                                    The gross transport rate is the sum of the left-
                                                                                    moving and right-moving transport and is always
                            Physical Processes                                      positive. Shoreline change due to longshore trans-
                                                                                    port is controlled by the net transport, whereas the
                            General Processes                                       volume of sand annually entering or being
                              The success of a shore-protection design de-          trapped by a navigation channel is related to the
                            pends on understanding the driving and control-         gross transport rate (the channel accepts material
                            ling mechanisms of sediment transport. As a             from both left and right), unless sand is unequally
                            means of providing background and uniformity to         blocked from the sides, as from jetties of unequal
                            the discussion, we will analyze the functioning of      length.
                            shore-protection structures in terms of the major          Cross-shore transport is further classified as
                            sediment transport processes and constraints.           onshore transport and offshore trunsport. Impor-
                              It is convenient, but somewhat arbitrary, to          tant beach change phenomena associated with
                            classify sediment transport direction as being ei-      cross-shore transport are seasonal changes in
                            ther alongshore or across-shore. Longshore trans-       beach width, storm-induced erosion, and post-
                            port denotes sediment movement parallel to the          storm recovery. Erosion by cross-shore transport
                            coast. On an open coast, it is mainly produced by       is promoted by higher water levels and higher,
                            wave breaking, which stirs and suspends the sedi-       steeper waves. Higher water levels can be pro-
                            ment and makes it available for transport by the        duced by onshore winds, storm surge (rise in wa-
                            longshore current. Waves breaking at an angle to        ter level accompanying storms and produced by
                            the shoreline produce such a current. Other             strong wind and differences in atmospheric pres-
                            mechanisms producing longshore transport are            sure), wave-induced setup, and long-period wave
                            barriers to waves, such as an island, jetty, or         motions such as surf beat, as well as by the tide.


                            82







                High water levels allow waves to act on portions           (5) water runoff and water table (concerning cliff
                of the profile not preconditioned to wave action,          erosion), (6) sediment supply, (7) geomorphic
                leading to erosion. Waves will typically have              controls (such as inlets and headlands), (8) geo-
                greatest steepness (wave height divided by the             logic controls, and (9) engineering controls
                wave length) at the peak of a storm and produce            (structures). An example of a geologic control on
                greater offshore transport (erosion); some of this         sediment transport is an effectively nonerodible
                material is returned onshore under the lower               rocky headland that might prevent sediment
                steepness post-storm (recovery) waves, as hap-             movement past it. The corresponding engineering
                pens as well during the summer. Kraus, Larson,             control is a long jetty.
                and Kriebel (1991) review the status of simple               Beach response to a shore-protection project
                predictions of direction of cross-shore sand               extended into the surf zone may be expressed
                transporL                                                  qualitatively as
                   When waves approach the coast at a small
                angle, rip currents (strong and narrow currents            Beach Response = F (wave and water
                that flow offshore) will form, and their strength           level parameters; sediment, geologic,
                depends on the height of the incident waves. Rip            and geomorphic parameters;                      (1)
                currents remove sand from the beach face and                engineering activities)
                surf zone and carry it offshore, beyond the region
                of breaking waves. This material may then slowly           where F means "a function of' and the phrase
                return to the surf zone or be deposited offshore.          engineering activities refers to actual structure
                Rips tend to form in the vicinity of structures that       (groin, breakwater, jetty), beach nourishment, and
                penetrate into the surf zone or beyond, such as            similar works. In most cases, the planner or engi-
                groins and jetties. They also tend to appear at            neer can control only parameters related to engi-
                discontinuities in the shoreline, such as at the           neering activities, but as much information as
                ends of a seawall if it projects into the surf zone        possible must be gathered about the first two
                (McDougal, Sturtevant, and Komar 1987) or at               groups of parameters on both the local and re-
                changes in the nearshore bathymetry such as de-            gional level to determine the optimal engineering
                termined by the geological structure (for ex-              design.
                ample, at a transition from rocky to sandy beach).         Oregon Coast
                On a long, sandy coast, during days of near-nor-             The Oregon coast is a high-wave energy coast,
                mal wave incidence, rip currents tend to occur             and it is remarkable that it exhibits only moderate
                with a longshore spacing of about one to four              beach erosion over most of its reach, the excep-
                times the width of the surf zone.
                   One other general concept entering our discus-          tions occurring mainly at spits. As an example,
                sion of shore protection is that of the littoral cell.     according to wave hindcasts performed by
                The word "littoral" refers to the active movement          CERC's Wave Information Study (WIS) group
                of sediment in the nearshore zone. A regional unit         (Jensen, Hubertz, and Paine 1989), at one WIS
                where the littoral zone is bounded laterally (along        station off Yaquina Head, in water 33 feet deep,
                the coast) is called a littoral cell. Boundaries of        the average significant wave height for the 20-
                littoral cells are commonly large headlands and            year hindcast period 1956-1975 was 9 feet, the
                jetties, inlets, and bays. Sometimes a littoral cell       highest significant wave was 24 feet, and the av-
                can be divided into smaller uiiits called subcells.        erage period of the most energetic waves was
                Typically, subcells are bounded by small head-             11.2 seconds. (Significant wave height is the av-
                lands or changes in shoreline orientation that re-         erage height of the highest one-third of the waves
                duce, but do not completely stop, longshore                in a wave observation.) The occurrence of large
                movement of sediment.                                      waves at Newport is also supported by measure-
                   Major sediment transport processes and con-             ments made at the Oregon State University Ma-
                straints that can control the transport am (1)             rine Science Center. In contrast, representative
                waves, (2) wind, (3) currents, (4) water level,            average arimial wave height and period on the
                                                                           mid-Atlantic coast are 3 feet and 8 seconds.


                                                                                                                                 83







                                Clemens and Komar (1988) provide an expla-            Sunamura, 1984, for more general discussion of
                             nation for the stability of Oregon beaches by the        the physical processes of cliff erosion). Sea-cliff
                             complete blockage of longshore movement of               composition is an example of the importance of
                             sediment by headlands. Much of the Oregon                the geologic setting of a site. Tectonic settling,
                             coast is formed of pocket beaches that can be            cliff composition, presence or absence of a pro-
                             considered individual littoral cells with little or no   tective fronting beach to inhibit wave action, fre-
                             exchange of sediment between cells. Seasonal             quency of storm occurrence, disposition of
                             shifts in wave direction move sediments along-           rainwater runoff, and presence of rip currents are
                             shore in an up- and down-coast motion with a             among the factors controlling cliff erosion. Prop-
                             potentially high gross transport rate, but the net       erly engineered shoreline stabilization structures
                             longshore drift is close to zero. The implication of     can provide cliff toe protection. However, enclo-
                             this physical situation is that a shore-protection or    sure of cliff sediments by seawalls and rubble-
                             navigation structure that may intercept longshore        mound barriers blocks material that would
                             transport would cause the least disturbance if it is     naturally erode, enter the littoral system, and con-
                             close to a headland terminus of the littoral cell. In    tribute to the volume of the adjacent beaches.
                             contrast, such a structure located in the middle of      Typically only a small percentage of a cliff s vol-
                             the cell would cause maximum disturbance by              ume is beach-quality material. Fine particles
                             interception of material from either the left or         originating from cliff erosion will move offshore
                             right that moves over a substantial portion of the       and out of the littoral system, and large rocks will
                             total cell.                                              remain in place. Water runoff from the top of a
                                It is also interesting that most of Oreg6n's          cliff is a geotechnical engineering problem that
                             sandy beaches consist of fine-to-medium sand.            can induce upper cliff failure by creating channels
                             Beaches on high-energy coasts usually consist of         and washing away material to gradually produce
                             coarser sand than those on moderate or low-wave          structural defects. Water also increases the weight
                             energy coasts. Yet the grain size on Oregon              of the soil and usually decreases its strength.
                             beaches is in the range of 0.2 to 0.3 nun, similar       Parking lot and street runoff, as well as runoff
                             to that on the east coast of the United States. The      from house roof tops and similar large volumes
                             explanation probably lies in sediment supply,            of controllable drainage water, should be directed
                             since the sands available to the Oregon coast are        around or through cliffs so as not to cause erosion
                             fine-to-medium grained.                                  or slope failures.
                                Rip currents on the Pacific coast can be very
                             strong and have the potential to transport large         Shore-Protection Measures
                             amounts of sand from nearshore to the offshore,
                             causing local erosion or an embayment. This phe-            To begin, we note that there are only four gen-
                             nomenon has been documented by, for example,             eral shore-protection responses to coastal
                             Komar and Rae (1976) (Siletz Spit) and Komar,            erosion:
                             Good, and Shih (1989) (Netarts Spit). Sand spits,           1. Relocation
                             formed by sediments that move alongshore from               2. Nourishment
                             the coast of the mainland, are typically low lying,         3. Stabilization structures
                             and embayments carved out by rip currents that              4. Combinations of elements of the above
                             tend to persist at certain locations on these spits
                             weaken the already fragile system.                          These responses, of wl-dch the first three are
                                Finally, bluffs and cliffs are major features         ordered from the most passive to the most active
                             along the coast of Oregon, and they are often de-        in terms of hardening of the coast with structures,
                             veloped for residential areas and recreational           are discussed individually below. In any case,
                             commercial property such as hotels, restaurants,         shore-protection responses are an integral compo-
                             and condominiums. Komar and Shih (199 1) pro-            nent in the overall sand management policy for
                             vide an up-to-date and authoritative description of      the coast and should not be implemented in
                             sea-cliff erosion along the Oregon coast (see            isolation.


                             84







                  The phrase "shore protection" is a generic term       based on risk to human life and the value of the
                that can refer to either beach stabilization or         resources protected or developed, and an effort
                backshore protection, or to both. Beach stabiliza-      must be made to account for both short- and long-
                tion can mean maintenance of a beach, that is,          term factors that may influence coastal evolution.
                promoting the existence of a beach (shore reten-        For example, in the Netherlands, sea dikes and
                tion), or it can mean shoreline stabilization, which    coastal dunes were designed to withstand the one
                implies fixing the position of the shoreline with-      in 100,000-year conditions. This level of protec-
                out specific regard to the condition of the beach.      tion is justified when entire cities lie behind the
                Backshore protection refers to protection of life       coastal defenses but is absurd for designing a
                and backland property from waves, flooding, and         beach fill to protect a parking lot on a recreational
                erosion. A particular shore-protection response         beach. Erosion is often episodic and beaches do
                will probably not serve all functions, and so in        usually fully recover, and the design life of a
                selecting the response or combination of re-            beach fill may be only five years, with replenish-
                sponses, it is vital that one be aware of the advan-    ment to be considered on an as-need basis (fine-
                tages and disadvantages of the response as beach        tuning). In summary, the level of protection and
                stabilization and backshore protection.                 life cycle must suit project needs, and monitoring
                   Shore protection includes the concept of life        and maintenance schedules are important ele-
                cycle, that is, a shore-protection structure has a      ments of an ovemll plan.
                certain service life. Typically, structures such as     Relocation
                roads, bridges, and buildings have a design life of        Relocation is moving existing resources, such
                about 50 years, and it is part of the project plan to   as residences, commercial buildings, and roads,
                maintain the structure over its expected life           landward to maintain a certain minimum distance
                through periodic inspection and repairs. Many lay       between the resource and the location of the erod-
                persons believe that coastal engineering activities     ing coastline. 'Me response of relocation is some-
                (for example, structures, beach nourishment) are        times called "retreat," an emotional synonym
                in some sense permanent. This is not the case.          with the nuance of limited planning and prepara-
                For example, coastal structures are built to with-      tion. As a planning concept and tool, relocation
                stand a certain average condition without notable       implies that permanent structures must be built
                degradation and to survive the oceanic environ-         beyond some predetermined line.
                ment up to a certain extreme condition called the          Set-back lines can be defined for both sandy
                design condition. However, routine inspection           beaches and cliffs, and relocation may be formal-
                and maintenance of coastal structures are re-           ized by a management policy that establishes
                quired. The design condition may be the 50-year         such a line along the coast. The set-back line may
                storm (wave and water level conditions which            be referenced to an erosion rate or to an inunda-
                occur on the average of once every 50 years). A         tion level (surge elevation associated with a storm
                structure may be damaged or fail if the design          of certain frequency of occurrence), or a combi-
                condition is exceeded (arrival of the 100-year          nation. A requirement for new construction to be
                storm or arrival of two 50-year storms in the           landward of the present shoreline position plus a
                same year), and extensive repairs may be                distance that will be reached in, say, 30 years, as
                required.                                      .      . determined by the local long-term recession mte,
                   The concept of a life cycle for structures is im-    is consistent with the concept of a human genem-
                portant, but difficult to quantify on the coast,
                where oceanic and meteorological conditions,            tion of 30 years or a structure life of about 50
                and hence erosion, are highly variable and not          years.
                fully predictable. Beach change can have a long-           The State of Florida legislated a set-back line
                term contribution, for example, gradual erosion         in 1970 as an interim measure while a study was
                owing to loss of updrift sediment supply, and an        underway to establish what is now called in
                episodic short-term contribution (ston-n-induced        Florida a "coastal construction control line"
                erosion). The formulation of design condition is        (CCCL). The objective was to determine the

                                                                                                                              85







                                CCCL based on sound technical criteria that had              sediment contributes to the littoral system,
                                to be developed for the purpose. The CCCL de-                thereby helping to retard erosion elsewhere. In
                                fines a zone of jurisdiction for the impact of the           principle, almost any structure can be relocated. If
                                100-year hurricane and is determined, in part, by            the cost is prohibitive, however, or if the cultural
                                numerical modeling of storm-induced beach ero-               value of the resource (an old fort, a lighthouse,
                                sion and the required wave and water levels. The             and so on) is attached to its location, other shore-
                                CCCL is applied on a county-by-county basis to               protection measures might be considered.
                                take into account differences in regional trends.            Nourishment
                                (Note that the Florida Division of Natural Re-                   Nourishment is the only form of shore protec-
                                sources restricts its jurisdiction to sandy beaches          tion that will maintain a shoreline that appears
                                and bluffs and does not include Federal land, har-           natural. The Federal Government has tradition-
                                bor complexes, and other developed coastal ar-
                                eas.) Construction seaward of 'the CCCL requires             ally nourished beaches for storm and hurricane
                                a permit, and no new residence is allowed within             protection, but not solely for recreational benefit.
                                the 30-year, long-term erosion limit. In principle,          The fill material may be emplaced by trucking
                                                                                             from an upland source; by pumping thmugh a
                                the 30-year limit is to be computed each time a              pipeline from an inlet, navigation channel, or
                                permit is issued to take into account most recent            back bay; or by dredging offshore and pumping
                                monitoring data and calculation procedures.
                                                                                             the sediment onshore. Bypassing at inlets or any
                                  Typically, one must design a shore-protection              littorul discontinuity in the shoreline (see the re-
                                structure, say a seawall, to withstand a 50-year or          view by Richardson [ 199 1 ]) is a way of control-
                                100-year hurricane. In an interesting twist of the           ling placement of sand on the beach and can be
                                conventional concept, present coastal zone mgu-              done according to a predetermined schedule, for
                                lations in Florida may now be replaced by the re-            example as a function of the amount impounded
                                quirement that such a structure withstand only a             at the updrift jetty of a channel. Clausner et al.
                                minor storm (perhaps a 5- or 10-year ston-n) and             (199 1) describe the functioning of a bypassing
                                fail for a larger storm. The idea is that the natural        plant at Indian River, Delaware, that exceeded the
                                force of a major storm or hurricane should be al-            project goal of bypassing 100,000 cubic yards per
                                lowed to reshape the coast uniformly. For ex-                year across the inlet. The bypassing rate is being
                                ample, if a property on the coast is protected by a          managed to balance the need for a recreational
                                well-engineered seawall and survives the 100-                beach on the updrift (south) beach at the inlet and
                                year event while adjacent beaches erode, the wall            beach nourishment needs on the receding
                                might become a littoral barrier interrupting conti-          downdrift (north) side of the inlet. Sand can also
                                nuity of the beach both for humans and sediment              be "backpassed," that is, returned updrift from a
                                transport. Eventually, such a barrier would prob-            downdrift impoundment area, and recycled into
                                ably be abandoned by the property owner if it be-            the littoral.system. Such a solution may be appro-
                                came stranded in the surf zone.                              priate for a spit receding because of longshore
                                  Relocation can be promoted in erosion-prone                0'ansport or the alongshore migration of a barrier
                                areas by zoning coastal lots to be of sufficient             island.
                                landward length to allow relocation over one or                 As with any construction project, the signifi-
                                two anticipated life cycles. This policy is a kind           cant mobilization expense associated with nour-
                                of preventive medicine that a priori recognizes              ishment makes it cost effective to place the
                                the potential for that coast to erode. Where practi-         maximum volume of material possible in a single
                                cable (recognizing that economics, politics, and          .  operation. There are physical masons for placing
                                nature, among other factors, define what is practi-          a substantial fill as well. If other factors (waves,
                                cable), relocation is becoming the preferred ero-            thickness of fill) are equal, the longevity of a fill
                                sion solution on lightly developed coasts. For the           is proportional to the square of its length (Dean
                                public and for the property owner, relocation pre-           1984; Larson, Hanson, and Kraus 1987). Benefits
                                serves the natural state of the coast and allows             of a fill extend past its original lateral boundaries
                                access to it. From the regional perspective, eroded


                                86






                  as the fill spreads (figure 2). Dean (1984) sug-             catastrophic dune erosion and inundation (Kraus
                  gests the formation of "erosion control districts"           and Larson 1988; Larson and Kraus 1989a,
                  through which several communities cooperate in               1989b).
                  placing fill over several miles. Ideally, the project           Beach nourishment can be used to construct or
                  should extend over a littoral cell or subcell.               maintain a recreational beach, protect hard coastal
                                                                               structures such as seawalls, provide an erosion
                                     Project Extent                            buffer for the backshore, and protect the backland
                                                                               from storm inundation. In the latter case, nourish-
                                                                               ment can be used for dune building-placement
                  Benefit                                         Benefit      of sand on the beach as a foredune and then pro-
                                                                               moting its growth through the placement of sand
                  Littoral                                   Littoral
                  Cell Boundary                              Cell Boundary     fences to capture wind-blown sand (see Hotta,
                                                                               Kraus, and Horikawa 1987, 1991 for reviews)
                                                                               and planting of vegetation (Corps of Engineers
                  Figure 2. Plan view of a beach nourishment project.          1972; SPM 1984). On a chronically eroding
                                                                               coast, dunes must be allowed to migrate landward
                    It is possible to create a littoral subcell at a           by wind-blown sand or they will be undercut like
                  nourishment project by enclosing the fill in                 cliffs and erode.
                  groins. These tenninal groins, which function as                The cost of a nourishment project is closely
                  short headlands, slow and reduce longshore                   related to the distance to the borrow source for
                  spreading of the fill. In a situation where the erod-        beach-quality material. Coarser material is ex-
                  ing beach is downdrift of a littoral barrier such as         pected to last longer, and this consideration is bal-
                  a jetty or large inlet, a groin field (series of             anced by haul distance. Often the source is
                  groins) may be placed with the fill. Groins are              obvious, such as littoral material that has shoaled
                  discussed below.                                             into a navigation channel and is removed as part
                    Beach nourishment material should be similar               of maintenance dredging. If this dredging is per-
                  to the native sediment in the littoral system. If it is      formed by the Corps of Engineers, then any in-
                  finer, the fill will tend to move offshore; if it is         crease in cost incurred by placement of the
                  coarser, the beach profile will resist erosion and           material on the beach beyond the least-cost han-
                  remain in place longer than the native material. In          dling procedure (the least-cost restriction man-
                  any case, as shown in figure 3, the profile of a             dated by Congress) must be bome by the local
                  nourished beach will adjust from the constructed             sponsor.
                  shape to a natural equilibrium shape according to               Finally, a recent development in beach nour-
                  the incident waves and sediment grain size. Dean             ishment practice is renewed interest and research
                  (199 1) provides a review of concepts of equilib-            in shallow-water placement of beach-quality
                  rium beach profiles. The public may perceive the             dredged material (see McLellan [ 1990] for a
                  apparent diminishing of the visible portion of a             review and engineering details). In this proce-
                  beach fill as a "loss." This may not be the case if          dure, which may be much less expensive than
                  the fill is simply moving out on the profile to                  20
                  achieve an equilibrium shape. The response of a
                  beach nourishment project to both typical and                     10                une   Berm
                  storm waves has become an active area of re-                                                  Construction Profile
                                                                                    0
                  search. Numerical simulation models are being                                                                              Figure 3. Adjustment
                  developed as design tools for estimating project             .2 -10 -                                                      of afill to the design
                                                                                                                         Design (Adjusted)
                                                                               >                                                             profile.
                  performance. Larson and Kraus (1991) review                                                                 Profile
                  the status of both longshore and cross-shore mod-               -20     Pre-Fill Profile
                                                                                                     D
                                                                                                            Be
                                                                                                              rm

                                                                                                                 Con sruct' on  Pro"'e




                                                                                                                         Des ign (Adjusted)
                                                                                                                              Prf, le
                                                                                      -@Pre- 11  @Profile
                  eling of beach fill. One goal is prediction of the              -30 1    1      1    1     1     1     1     . - .- -
                  initial adjustment of the fill to the design profile,             -200   0    200 400 600 800 1000 1200 1400
                                                                                                  Distance Across-Shore (ft)
                  but the major objective is evaluation of potential


                                                                                                                                        87







                             direct placement on the beach, dredged material          stones. A variety of concrete armor units are
                             is deposited in shallow water (typically, by split-      available as alternatives to stone. These units are
                             hull barges), in the form of a long linear ridge that   . employed in very large wave conditions or in
                             is like a naturally occurring longshore sand bar.        situations where stone of sufficient size or quality
                             Benefits may be direct (when the material moves          is not available. The availability of stone gener-
                             onto the beach) or indirect (when the material           ally makes it the cost-effective alternative for
                             causes storm waves to break farther offshore).           typical revetments in Oregon.
                             McLellan and Kraus (1991) describe preliminary              Care must be exercised in the selection and
                             design criteria for shallow-water material               placement of armor stones. The stone must be
                             placement.                                               durable and free from cracks, and materials that
                             Stabilization Structures                                 weather, abrade, chemically degrade, and so on,
                                Them are a variety of structural alternatives for     should be avoided. Rounded stones, such as river
                             stabilizing shorelines. These are often referred to      boulders, stones with one very short axis, and
                             as hard structures. Hard structures establish a          stones with one very long axis, should also be
                             fixed or approximately fixed position for the            avoided. These shapes correspond to spheres,
                             shoreline defense. The position of the natural           plates, and rods; unless very special placement
                             shoreline is dynamic. It can change with storms          techniques are employed, these odd-shaped
                             and season and have a general trend over long            stones will result in low levels of stability. The
                             periods. Placing permanent structures such as            SPM (1984) provides guidelines for the specifica-
                             houses, hotels, roads, and bridges on the beach          tion of armor stone. Armor stones should be
                             conflicts with the dynamic response of the shore-        placed, not dumped. If stones are dumped on a
                             line. A structure that establishes a fixed line of       slope, they will segregate by size with the larger
                             defense must have sufficient structural integrity        stones being at the toe. Standard practice is to
                             to withstand large waves, hence the term "hard           nest the armor stones in a layer two stones thick.
                             structure." A soft structure, such as a beach fill, is      In the U.S., the required size of armor stone is
                             much more compliant. It will experience large            determined using Hudson's equation (SPM
                             displacements and possibly major erosion during          1984). If the revetment is built with angular
                             a design event.                                          quarry stones at a slope of I V: 1.5H, then the re-
                                In this section we review the functional behav-       quired stone weight is approximately
                             ior of several types of hard structures commonly                           W= 16    d 3(2)
                             used to provide shore protection (see also Dean
                             [ 1986]). These are, in order of coverage, revet-        in which W is the weight in pounds and d is the
                             ments, seawalls, groins, detached breakwaters,           water depth at the revetment toe in feet. The
                             floating breakwaters, and combination structures,        depth .is for the high-water storm condition and
                             typically with beach fill. We consider fully engi-       must include storm surge, astronomical tide, and
                             neered structures, and not low-cost shom-pro-
                             tection measures (Corps of Engineers 1980)
                             that are not expected to have a long life cycle.
                             Revetments                                                            beach gross
                                Riprap revetments are the most common
                             hard structure employed for shoreline stabili-
                             zation on the Oregon coast. A typical revet-             sand     op ing                     armor stone
                             ment is shown in figure 4. It consists of             --- @
                                                                                                                   filter fabric
                             several key components: filter fabric or bed-
                                                                                                                     or bedding layer
                             ding layer, armor stones, toe trench, sand top-                      toe  trench
                             ping, beach grass, and backshore drainage.
                             The most conspicuous component is the
                             armor layer that is constructed from large            Figure 4. Schematic of a typical revetmeta.


                             88






               scour. This simplified equation is valid only for       Seawalls
               structures shoreward of the wave breaker line (the         The terms seawall, bulkhead, and retaining
               typical situation in Oregon). If the total design       wall are often used interchangeably. To be more
               depth is 3 feet, a stone weight of approximately        precise, a seawall provides stability against
               430 pounds would be stable. If the depth is 6 or        waves, a retaining wall provides geotechnical sta-
               10 feet, the resulting weights are approximately        bility for a slope, and a bulkhead provides both
               3,500 and 16,000 pounds. This simple example            functions. We will use the term seawall as it is
               clearly demonstrates the importance of water            commonly used in Oregon to encompass all of
               depth on design and stability of the structure. The     these cases. There are several circumstances un-
               higher the revetment can be placed on the beach         der which the selection of a seawall may be the
               profile, the more stable it will be for a given stone   appropriate structural alternative: (1) There is in-
               size because it is not attacked by large waves.         sufficient space between the zone line and struc-
                  The filter fabric, or bedding layer, performs        tures on the property to install a sloped revetment.
               two functions. It prevents the an-nor stones from       (2) The bluffs behind the seawalls are unstable
               sinking into the sand, and the permeability of this     and susceptible to slope failure or landslides.
               underlayer allows pore-water pressure beneath           (3) The developer wants to extend the lot seaward
               the revetment to be released. If a fabric is used, it   by filling behind the seawall.
               should have a pore size that will contain the un-          Seawalls may be built in several ways, gener-
               derlying beach sand, have a high permeability,          ally as cantilevered structures (sheet piling) or
               not degrade in ultraviolet light, and have suffi-       gravity structures (concrete seawall). Several
               cient puncture strength not to be damaged by the        types of structures are shown in figure 5. The
               armor stones.                                           pile-type seawall may be constructed using tim-
                  The toe trench is an essential component of the      ber, concrete, or steel. For the timber case, piles
               revetment. Under storm wave conditions, much            are driven and planks are placed across the piles.
               of the sand fronting the structure may be re-           Concrete or steel H-piles may be used with con-
               moved. Without a toe trench the revetment would         crete panels or timber placed in the slots within
               be undermined and collapse. A rule of thumb for         piles. Conventional steel sheet piling may also be
               the depth of the toe trench is that it be excavated     used. Tie-backs may be used to reduce the bend-
               either down to bed rock or to the water table.          ing moment in the piles. Gravity seawalls may be
               When either of these condi-
               tions is encountered, the costs                             sheet piling
               associated with continued ex-
               cavation are prohibitive for                                                              concrete gravity
                                                                                                             tructure
               most small revetments.
                  Topping the structure with             tie back
               sand and planting beach grass                                                                     scour
               almost eliminate adverse visual                                                                     protection
               impacts. Most of the time the
                                                                            scour              bedding  layer
               revetment will appear as a                                    protection                                          Figure 5.
               steep slope vegetated with                                                                                        Examples of
               beach grass. Under storm con-                                                  geotextile bogs                    seawalls.
               ditions, sand and grass on the
               lower structure will erode, ex-
               posing the armor. Details re-                                                          scour protection
               garding planting and cam of
               beach grass are given in Corps
                                                                                                "'o " 4

                                                                                                                 scour
                                                                                                                   prote














               of Engineers (1972).                                              filter fabric





                                                                                                                            89







                              built that have a large cross-section and maintain      bar development during storms. The formation
                              stability through their self-weight. Gravity            during storms of a large breakpoint bar (built
                              structures reduce or eliminate the need for driving     from material from the upper profile) is the usual
                              piles. However, the material requirements am            storm response of the beach. In front of a seawall
                              much more substantial. Gravity structures may be        or revetment, sand to develop a bar may come
                              constructed from concrete or geotextile bags            from unprotected properties adjacent to the struc-
                              filled with sand or gravel and stacked to form the      ture. 'Merefore, the structure may increase ero-
                              structure. Bag and tube seawalls have been suc-         sion on adjacent properties, as shown in figure 6.
                              cessfully employed but are susceptible to damage        This has been observed in the laboratory and after
                              from drifting logs (a common problem in the Pa-         hurricanes on the Gulf coast (Walton and
                              cific Northwest) and vandalism.                         Sensabaugh 1978; McDougal et a]. 1987). How-
                                 Wave forces acting on a seawall can be sub-          ever, a five-year program curTently underway
                              stantial. When a wave strikes the wall, large           monitoring revetments and seawalls in Oregon
                              flows are directed both up and over the structure,      does not support this observation. The Oregon
                              and down toward the bottom. The upward flow             coast has many areas with high, weakly cemented
                              may result in undesired spray and even green wa-        bluffs that are often oversteepened by wave-in-
                              ter over the top of the structure. For this reason,     duced erosion at the toe. The bluff face then
                              some seawalls are slightly curved seaward to di-        sluffs or is winnowed away by wind and rain. A
                              rect the upwash away from the shore. At the toe,        seawall or revetment reduces or eliminates toe
                              the structure is exposed to large hydraulic forces,     erosion and also reduces winnowing of the bluff
                              often making it necessary to place rubble to pre-       face. Some of this benefit extends to the adjacent
                              vent erosion or a scour pit. Toe scour is a com-        unprotected properties. Preliminary field results
                              mon mode of failure for seawalls.                       suggest that this stabilizing effect is more impor-
                                Seawalls can provide a high level of protection       tant than the demand for sand for bar develop-
                              for the property backing the structure. However, a      ment during storms. Griggs et a]. (1991) discuss
                              seawall provides no protection for the beach, and       the results of a four-year seawall monitoring pro-
                              the location of a seawall relative to the shoreline     grain along a pocket beach in southern California.
                              is an important parameter (Weggel 1988). Sea-           Komar and McDougal (1988) describe observa-
                              walls and revetments may have several adverse           tions of seawall and beach interaction on the Or-
                              impacts on the littoral system. An overview of the      egon coast.
                              effects of seawalls on beaches is given in Kraus            A natuml location for beach access trails is at
                              (1987, 1988), and an edited collection of papers        the end of seawalls and revetments. In these ar-
                              on this topic is contained in Kraus and Pilkey          eas, beach grass is destroyed and the dune and
                              (1988). The universal effect is that sand im-           upper beach profile elevations am reduced. This
                              pounded behind the structure cannot participate in      weakened location will be more susceptible to
                                                                                      erosion during storms. Since the ends of struc-
                              101                                                     tures are already a vulnerable location, beach
                                                                                      trails should not be developed in these areas.
                                  I-    LS-1
                                                          _Ie
                                                                   *a    A6           Groins
                          E   10                                                         A groin is a thin, long structure oriented nor-
         Figure 6.        Z@                                                          Mal or nearly normal to the shoreline. In some
                          0                                         field data
         Erosion          @')  I                                                      areas of the U.S., groins are colloquially referred
                          0
         adjacent to a    X
         seawall.         W                               @r = 0.10Ls                 to as "jetties" by the lay person, but this usage is
                          V)
                          (n                010                                     - not. correct; a jetty is a structure built normal or
                          LU  10-1-       610
                          U                        laboratory
                          X
                          LLJ         Zo           data                               nearly normal to the shoreline at an inlet to pro-
                              10-d                                                    vide wave, cunrnt, and sediment transport reduc-
                                1CF,                     10          to'            103 tion for vessel navigation. Therefore, jetties am
                                         STRUCTURE LENGTH, Ls (meters)                located exclusively next to entrance channels, and



                              90







                 their primary purpose is navigation-related and           tion the beach slope will be steeper. On the
                 not shore protection. A straight groin is the sim-        updrift side of a groin, the longshore current must
                 plest and most common kind. Various lateral               be turned offshore and probably carries some
                 appendages can be included to form T-shaped               sediment with it. Also, a rip current may form at
                 groins, spur groins, and so on (SPM 1984). Such           the groin.
                 appendages shadow a portion of the shoreline                 Groins are relatively ineffectual if them is a
                 from direct wave action, acting like a breakwater.        strong component of cross-shore transport, such
                 They may also reduce offshore loss of sediment            as on the Great Lakes. There, frequent summer
                 carried by the seaward flow of rip currents near          and winter squalls and the recovery waves that
                 shore-normal structures. Here we restrict discus-         follow readily move sediment across the profile.
                 sion to straight groins aligned non-nal to the            Once offshore and beyond the tips of groins, the
                 shoreline.                                                sediment can move alongshore.
                   A summary on the functioning of groins and                 The offshore and longshore extent of the fillet
                 the response of the shoreline to them is contained        (and, conversely, the landward and longshore ex-
                 in the SPM (1984), with a useful compilation of           tent of the downdrift eroded area) will depend on
                 information given in Balsille and Berg (1972).            the length of the groin. It logically follows that
                 Although a groin appears to be a simple structure,        the longer the groin, the greater the extent of the
                 the interaction of the driving forces (waves and          accreted and eroded areas. In principle, sediment
                 currents) with the beach and groin is surprisingly        can move alongshore and past a groin in four
                 complex. At present, available guidance on groin          ways: (1) passing around it on the seaward end
                 functioning is empirically based and must be em-          (bypassing), (2) passing over it, (3) passing
                 ployed with caution. Research at CERC has re-             through it, and (4) passing behind it. The latter
                 cently been initiated to use numerical modeling           situation of sediment passing behind a groin
                 of shoreline changes (Hanson and Kraus 1989;              means the groin has been flanked and is undesir-
                 Gravens and Kraus 1989; Hanson and Kraus                  able because the groin can become isolated.
                 1991b) to develop more widely applicable and              Therefore, groins must be built far enough land-
                 reliable design guidance. This work is being veri-        ward to prevent this occurrence.
                 fled with field data. As an example, in the CERC             Movement of sediment over a groin is con-
                 modeling investigation, 20 variables have been            trolled by its crest elevation relative to the water
                 identified as being in the schematic equation (1)         level and depends on the groin elevation, tide
                 relating beach response to forcing, beach, and            level, and wave height and direction. Movement
                 structure groups of variables.                            through the groin depends on the groin's perme-
                    A groin performs its protective function by            ability (amount of void space that allows water
                 extending into the surf zone to intercept a portion       and sediment through). Well-engineered, imper-
                 of the longshore sand transport. Intercepted or           meable groins usually have an elevation that de-
                 trapped sand is no longer available to downdrift          creases with distance offshore to allow
                 beaches. Therefore, as shown in figure 7, if the          overtopping of water and sediment as a way of
                 predominant direction of transport is to
                 the left, a fillet will form on the right
                 side of the groin, and erosion will occur               Predominant direction         Possible rip current
                 on the left, with the "shoreline signa-                 of transport            <
                 ture" being approximately an inverted                                                  Gro n-adj  sted shoreline     Figure 7. Schematic
                 version of the signature of the fillet (a                                                   (Milder beach  profile)  of beach planform at
                 slight difference may occur due to                        (Steeper beach profile) <                                  a groin.

                 glected here for simplicity). Typically,
                 wave diffraction and rip currents, ne-


                                                                                                                 Original  shoreline
                                                                                                           I '   -u-_
                                                                                                  <L('M,ide'r bea


                 the beach slope along the accreted area
                 will be milder than along the original                    Possible flanking
                 beach, whereas along the eroded sec-



                                                                                                                                  91







                              allowing some sediment to move alongshore.
                              Groins constructed by the Corps of Engineers
                              typically are rubble-mound structures with an
                              impermeable core and have a relatively long de-
                              sign life.
                                 Durable king-pile groins have been con-
                              structed consisting of concrete pilings into which
                              planks can be stacked from the sea bed upward,
                              with the elevation controlled by the number of
                              planks. In principle, the amount of material pas
                              ing over and through such a groin can be con-
                              trolled. In practice, however, adjustment and              Figure 8. Groins at Newport, California. North is to the
                              replacement of the planks is not easy. Neverthe-           right in thisfigure. (Courtesy ofA. Shak, U.S. Army
                              less, on a city or state level, the use of devices         Engineer District, Los Angeles.)
                              that have a fine-Mning mechanism incorporated
                              in their design is recommended. Such structures
                              are limited to relatively low-wave energy envi-
                              ronments in which construction equipment can
                              operate. Groins have also been constructed using
                              timber, steel, and concrete sheet piling and sand-
                              filled coffer darns.                                                                             A
                                 An interesting political and legal question that
                              has arisen with adjustable structures is, who is
                              responsible for adjusting the groins? It is a prob-
                              lem because of all the associated economics, per-
                              mitting, and legal consequences that would result
                              should updrift or downdrift shorelines erode. This         Figure 9. Groins at Long Beach, Long Island, New York.
                                                                                         East is to the right in thisfigure. (Courtesy of G. Nersesian,
                              type of problem is a challenge to coastal manage-          U.S. Army Engineer District, New York.)
                              ment policy.
                                 Groins are typically built in "fields," meaning         groin field at Long Beach, Long Island, New
                              two or more groins in series. Groin fields might           York. It is standard practice to place a beach fill
                              be particularly appropriate downdrift of long jet-         in groin compartments, and possibly a feeder
                              ties or headlands that intercept the longshore             beach so that the groin field will not entrap sand
                              movement of sediment. The objective is to pro-             moving along the coast. However, some accumu-
                              tect the beach in the compartments between the             lation updrift of the groin field can be expected.
                              groins and mitigate impacts on the adjacent                The conceptual solution, shown in figure 10, is to
                              beaches. Figure 8 shows long groins off Newport,           taper the groins with gradual reduction in effec-
                              California, holding a protective beach for the             five groin length towards the ends of the field.
                              coastal highway, and figure 9 shows a part of the          "Effective groin length" means the length in the


                                                                                                                                      Wove
                                                                                                                                        ests


                                                                                      Tapered groi                 Groin-adjusted
                                                                                                                      shoreline
                                          Figure 10. Schematic
                                          of tapered groins.
                                                                                                                    Initial




                                                                                                                       Original shoreline





                              92







                 active surf zone. If there is substantial net trans-    tively deep water. If there is a beach in the lee of
                 port to the left and right, the tapering should be      the breakwater, the shoreline may respond to the
                 done on both ends of the groin field.                   presence of the structure because of its great
                  The two questions asked early in the process           wave shadowing (the desired feature for naviga-
                 of functional design of groin fields are (1) how        tion safety). This type of breakwater is not con-
                 long should the groins be? and (2) what should          structed for shoreline protection and will not be
                 the spacing between groins be? These are central        discussed further.
                 questions to be answered by numerical modeling             As a shore-protection device, a detached
                 now underway at CERC. For the present, the con-         breakwater is typically 100 to 300 feet long, and
                 ventional answers are that the effective groin          is usually placed somewhat farther offshore than
                 length should be approximately 40 to 60 percent         the average width of the surf zone. The important
                 of the width of the average surf zone, and the          concept is that the structure is detached or sepa-
                 spacing between groins should be about four             rated from the shoreline and hence, in principle,
                 times the effective length. Numerical modeling          sediment can pass alongshore between it and the
                 results are expected to refine this simple guidance     shoreline. The amount of sediment that passes is
                 by incorporating other major factors appearing in       an important factor in the functional design of a
                 equation 1.                                             breakwater. Detached breakwaters can be built
                   As previously mentioned, it is recommended            alongshore in series, analogous to a field of
                 practice to fill groin compartments during con-         groins, to protect a long stretch of shoreline. Such
                 struction; the filling starts at the most downdrift     multiple detached breakwater systems are re-
                 end of the beach segment to be protected and pro-       ferred to as segmented detached breakwaters.
                 ceeds in the updrift direction that is occurring        The length of the gap between breakwater seg-
                 during the period of construction. (Note: the           ments becomes an important parameter, together
                 updrift direction depends on the wave direction         with the length of the breakwater, its distance off-
                 during the season of construction and is not nec-       shore (or, equivalently, the depth at the structum),
                 essarily the predominant direction of drift, which      and the wave trarismission at the structure, which
                 is an annual average.) Also, a feeder beach may         is discussed further below.
                 be placed at the downdrift end of the field to pro-        There are three general shoreline responses to
                 vide material to the adjacent, nongroined beach         a detached breakwater, as shown schematically in
                 until the shoreline position comes into dynamic         figure 11. These are a tombolo, a salient, and lim-
                 equilibrium with the groin field.                       ited response. A tombolo is a word of Italian ori-
                 Detached Breakwaters                                    gin that refers to the bridge of sand or sediment
                   Detached breakwaters = structures that are            that grows from did mainland beach to a detached
                 built offshore and are almost always aligned par-       breakwater (or to a small island or a rock outcrop
                                                                         that is located relatively near to shore). A salient
                 allel to the trend of the local shoreline. Detached     is a structure-induced beach cusp that grows out
                 breakwaters are sometimes referred to as "off-
                 shore breakwaters." Because most coastal
                 structures are, in some sense, located off-
                 shore, this expression is somewhat inappro-
                 ptiate. Detached breakwaters are built for              20
                                                                        c                                    - Tombolo
                                                                        .2
                 two, usually independent, purposes: (1) as             .6                                      - Salient
                 breakwaters to improve navigation and                  COL 10                               -Lim. Response         Figure 11.
                                                                                                                                    Schematic of
                 (2) as shore-protection devices. The first                                                                         shoreline response
                                                                                                                                    to a detached
                                                                        0
                 type of application primarily concenis wave               0
                                                                        LO
                 sheltering at the entrance to a large harbor.
                 The breakwater is typically several hundred            -10
                                                                            0        200        400       600       800        1000
                 to a few thousand feet long and may be lo-                                Distance Alongshore
                 cated thousands of feet offshore in rela-




                                                                                                                               93







                              from the beach but reaches equilibrium size be-           may reduce water quality, they prevent some por-
                              fore reaching the breakwater. Limited response            tion of sand from reaching the downdrift coast,
                              denotes either that there is no change of engineer-       and they are a hazard to or prevent some recre-
                              ing significance in shoreline position or that there      ational activities such as surfing. The construction
                              is small salient growth that is either transient or       costs are high because work must usually be done
                              seasonal. At the beginning stage of shoreline re-         from a barge or trestle. In low-wave environ-
                              sponse to a detached breakwater, the shoreline            ments and seasons, it is feasible to construct a
                              directly opposite both ends of the structure can          breakwater by building a sand road from shore to
                              erode. As the shoreline-breakwater system ap-             the site, then operating a crane from the end of
                              proaches equilibrium, the eroded areas will tend          the road to place the construction material. The
                              to fill in. If the length of the detached breakwater      material making up the road can then be removed
                              is large in comparison to the width of the surf           or redistributed as initial fill. View degradation
                              zone, salients or tombolos may form at each end.          may be reduced by using submerged detached
                                 From about the 1960s, numerous detached                breakwaters (Ahrens 1989). However, wave pro-
                              breakwaters have been built in Japan as a pre-            tection decreases as the depth of submergence
                              ferred shore-protection measure, although in the          increases.
                              Uriited States a limited number of such structures          The wave transmission coefficient KTof a
                              were built as early as the 1930s. After a decline in      breakwater is defined as the ratio of the height of
                              use in the United States, some substantial de-            the waves just seaward of the structure to the
                              tached breakwater projects are now being built on         height on the landward side. The value KT= 0 im-
                              relatively low-wave energy coasts-6 breakwa-              plies that no waves pass over or through the
                              ters at Holly Beach, Louisiana (Nakashima et al.          breakwater, and a value of KTclose to unity im-
                              1987, Hanson, Kraus, and Nakashima 1989) and              plies that the structure has little effect on the
                              58 breakwaters under construction at Presque              waves. Breakwaters built to shelter navigation are
                              Isle, Ohio (Mohr and Ippolito 1991).                      typically high and impermeable (for example,
                                 Detached breakwaters have a number of ad-              made of sand-filled concrete caissons), whereas
                              vantages over groins as a shore-protection device.        detached breakwaters built for protecting the
                              If a tombolo is required (as can be created by            shore are usually designed to have some wave
                              beach fill, a common method of construction in            transmission by (1) setting the crest elevation to
                              the Chesapeake estuary, Virginia), an artificial          allow a portion of the higher waves to pass over,
                              headland is formed. If a salient is required and          and (2) making the breakwater permeable to al-
                              approximately formed by placing fill on the               low wave energy to pass through. Breakwaters
                              beach behind the structure, the majority of sand          that have low transmission coefficients experi-
                              moving alongshore can pass the breakwater and             ence less wave force and tend to last longer. Also,
                              move to downdrift beaches. Detached breakwa-              because the cost of the material composing a
                              ters can provide a sheltered area in the ocean            breakwater is proportional to the volume of the
                              beach environment for waders and swimmers                 structure, hence roughly proportional to the cube
                              who desire calmer water than that on the open             of its elevation, it is economically advantageous
                              coast away from the breakwater, however, a                to build low breakwaters. Figure 12 shows nu-
                              strong diffmction current directed offshore should        merical simulations of shoreline planform behind
                              be avoided in such an application. The diffraction        a detached breakwater as a function of the trans-
                              current can be reduced by increasing wave trans-          mission coefficient (Hanson and Kraus 1989,
                              mission at the breakwater. Detached breakwaters           1990).
                              made of rubble mound or armor blocks tend to                Water quality problems may be reduced by
                              enhance sea life and fishing, although fishing            increasing the gap size between breakwater seg-
                              from or near breakwaters may be hazardous.                ments. Areas with both low waves and low tides,
                                 The main disadvantages of detached breakwa-            such as the Mediterranean, are susceptible to wa-
                              ters are that they are expensive to construct, they       ter quality deterioration because of a lack of
                              are considered by many to be unaesthetic, they            flushing. Sand blockage problems can be reduced


                              94







                by (1) placing fill from an upland or off-
                shore source behind the breakwaters, (2)                   20
                increasing the gap size to allow more wave         E       15                                                K,  Figure 12.
                energy to pass shoreward, and (3) placing          c
                                                                   0                                                         0.0 Calculated
                                                                                                                             0.2 shoreline response
                the breakwaters in shallower water so that         10      10                                                0.4 at a detached
                sand bypasses alongshore and around the                                                           - - - 0.8      breakwaterfor
                                                                   .=@     5
                outside of the structures during storms.           1W                                                            different wave
                                                                   0                --------------------
                                                                           0                                                     transmission
                  For the beach response to detached                                                                             coefficients.
                breakwaters, at least 14 parameters enter                  -5-
                equation (1) (Hanson and Kraus 1990). The                  0        100     200        300        400        500
                                                                                         Distance Alongshore (nn)
                engineer can control only those parameters
                associated with the structure (except for
                sediment supply if a fill is added), and Hanson            large box section which has a draft of approxi-
                and Kraus found useful nondimensional param-               mately 5 feet. This type of structure is reasonably
                eters to be the length of the structure relative X to      effective at reflecting small waves. The floating
                the length of the average waves at the structure L,        tire breakwater is an example of a dissipative
                and incident wave height in deep water HO rela-            breakwater. Used tires are connected to form a
                five to water depth at the structure D, and the            buoyant mat. These mats of tires are then moored
                wave transmission coefficient K,- Figure 13                to float on the free surface. As the water flows
                shows the results of intensive numerical simula-           through the tire modules, incident wave energy is
                tions of shoreline change with many combina-               dissipated as turbulence.
                tions of these variables (Hanson and Kraus 1990).          Many other VyWs of floating breakwaters have
                It is seen that tombolo formation, salient forma-          been proposed, including submerged flaps,
                tion, and limited shoreline response fall into dis-        spheres, A-frames, and inclined pontoons. These
                tinct regions. By using this figure, prepared for a        structures have been found to be effective for
                beach with 0.2-min mean diameter sand, the                 relatively narrow ranges of wave conditions.
                planner or engineer can make a first estimate of           Floating breakwaters are generally less expen-
                the functional design of a detached breakwater             sive to construct than conventional fixed struc-
                according to the wave climate and beach slope of           tures such as revetments, seawalls, and rubble
                concern.                                                   breakwaters. They also have the advantage of
                  Sources of information on shoreline response             fabrication on land for-towing into position.
                to detached breakwaters and their functional de-           Floating breakwaters may be installed quickly to
                sign include the SPM (1984), Dally and Pope                provide a rapid response to the need for
                (1986), and Pope and Dean (1986). Recent nu-               protection. They may also be removed and
                merical modeling simulation advances in shore-             installed seasonally, a particularly useful feature
                line response to detached breakwaters are                  in areas where freezing occurs. Disadvantages of
                described by Hanson and Kraus (1989, 1990,                 floating breakwaters are that they do not provide
                1991a, 1991b).
                Floating Breakwaters                                       14-      X X      X     X                         0
                  Floating breakwaters have been used on                   X12-          X X             X        0
                low-wave energy coastlines with some suc-                  10       X X     X      0
                                                                                                                                 Figure 13.
                cess to provide shoreline stabilization (Hales             _j8%=Xx.." x.,xXxx 0
                                                                                                                                 Classification of
                                                                              X
                198 1). Floating breakwaters work by either                3:                                                    shoreline response
                                                                           6    x   . xx     0     0              0          0   to detached
                reflecting or dissipating waves. Typical float-            S  .. X X X      0            0        0
                                                                           1@4xxx   x       0      0                             breakwaters.
                ing breakwaters am shown in figure 14. An                  0          Oc O@        0
                                                                           .? XX    X       %0
                example of a reflective floating breakwater is             i52-X    e 0
                                                                           ZX                  Lim. Res  x salient 0 Tornbolo
                                                                                    x X




                                                                                    x x

                                                                                      x
                                                                                         x  x
                                                                                             x




                                                                                                   0
                                                                                            0
                                                                                                   X






                                                                                         x
                                                                                                         x







                                                                                             0     0              0
                                                                                            0            0        0
                                                                                         X




                                                                                    x x
                                                                                    x
                                                                                    x       0      0
                                                                                            000    0
                                                                                    X q  0
                                                                                      0     @L, rn. @Re sx @Sa
                                                                                                            fiento@o
                                                                              X__ X X
                                                                              X-.
                                                                              ` X
                                                                              __X   X
                                                                              XXX
                                                                              XX
                                                                              X
                                                                           X
                                                                           of
                the pontoon section, which can be fabricated               0
                                                                           0    0.2   0.4   0.6    0.8    1       1.2        1.4 1.6
                from steel, concrete, or wood. It is typically a                    Relative Wove Height (1-KT) HO/D



                                                                                                                             95








                                                              Floating pontoon                                    Floating tire
                                                              breakwater                                          breakwater







                              Figure 14.
                              Examples of
                                                                                                                               7
                              floating
                              breakwaters.







                                                                                                                 Submersed float
                                                                                                                 breakwater






                              protection for long-period waves, they are very         will also occur for offshore breakwaters that are
                              difficult to moor in large seas, and they have          not. properly filled with sediment. For these two
                              higher maintenance requirements than other              structural alternatives to be viable in comprehen-
                              methods of stabilization. For these reasons,            sive planning, they must be combined with beach
                              floating breakwaters are not a viable alternative       fills.
                              for open-ocean applications on the Oregon coast.           Another combination example is a perched
                              Combinations of Shore-Protection Responses              beach. In this case a very low submerged break-
                                Combined shore-protection measures are be-            water, or sill, is built in the offshore. This small
                              coming a more common design alternative, due            structure will somewhat reduce incident wave
                              in part to a comprehension of the needs of both         energy into the surf zone, tending to stabilize the
                              shore retention and backshore protection, and to        sand on the beach. In addition, a beach fill is
                              our increased capability to develop successful          placed so that its seaward end is supported by the
                              functional designs. Two major examples are the          sill or submerged breakwater, as sketched in fig-
                              combination of beach fills and groins, and beach        ure 15. The perch can be constructed as a nibble
                              fills and detached breakwaters. As discussed            structure or as a concrete structure using prefabri-
                              above, a groin field in which the compartments          cated modules. However, sand moving offshore
                              are not filled with sand will result in a significant   and over the sill cannot jump the sill and return.
                              reduction of sediment supply to the downdrift              A low breakwater supporting a perched beach
                              beaches. The same downdrift losses of sediment          will not significantly reduce large waves. In this
                                                                                      case, a substantial portion of the fill may be lost,



                                                                       Pearched beach

                              Figure 15.
                              Schematic of
                              a perched
                              beach.
                                                                                                                      Submerged
                                                                                                                      breakwater
                                                    Original
                                                    beach profile



                              96







                 and the backshore may erode. Therefore, a small               retention or backland protection. Table I below
                 revetment can be placed beneath the fill that                 summarizes the applicability of each major
                 would be visible and provide protection only in               category of alternative, together with an estimate
                 extreme events. Because the waves are somewhat                of the relative cost for typical situations. Site-
                 reduced by the submerged breakwater, the size of              specific circumstances (for example, availability
                 the revetment could be less substantial than an               of material such as fill and accessibility to the
                 exposed revetment. For relatively low energy                  site) may alter the relative cost.
                 conditions, a number of commercially available                  In a comprehensive coastal management plan,
                 prefabricated concrete mats are available. They               which is one that covers a regional scale (at least
                 may be installed by hand before the fill is placed.           the littoral encompassing the site and a reasonable
                    Structures at the ends of littoral cells can re-           project life cycle), a combination of the above
                 duce loss of sand from the cell, and some portion             alternatives is probably necessary for a balance
                 of this sand can be either bypassed or backpassed,            between shore retention and backland protection.
                 according to the situation. Beach-quality sand
                 dredged from navigation channels may be placed
                 directly on shore or in the form of linear bars in            Acknowledgment
                 the offshore. Such mounds of sand function simi-                We are grateful for the cooperation of the indi-
                 lar to a highly transmissive detached breakwater,             viduals who supplied photographs for this work,
                 but one that may also deflate and supply sand to              as acknowledged in the figure captions. We thank
                 the littoral system and beach.                                Dr. Clifford Truitt for informative discussions
                                                                               and review of this paper. The work of N.C.K. was
                 Concluding Discussion                                         conducted at the Coastal Engineering Research
                                                                               Center, U.S. Army Waterways Experiment Sta-
                    This paper has given an integrated overview of             tion, as an activity of the Beach Fill Engineering
                 shore-protection engineering alternatives. Cita-              work unit of the Coastal Program, U.S. Army
                 tions in the text direct the interested reader to             Corps of Engineers. He appreciates permission
                 more detailed technical information. Most alter-              granted by Headquarters, Chief of Engineers, to
                 natives have a large experience base in case stud-            publish this information.
                 ies, and literature on numerical simulation of
                 beach evolution under single and combined alter-              References
                 natives is also available.
                    In approaching a shore-protection problem,                 Ahrens, J.A. 1989. Stability of Reef Breakwaters,
                 planners should determine whether they want a                   Journal of Waterway, Port, Coastal and Ocean
                 shore-protection alternative to ftinction as shore              Engineering, 115,221-234.



                         Alternative              Shore Retention              Backland                   Cost
                                                                               Protection

                   Relocation                     High                     Low                    High (developed
                                                                                                  area); Low
                                                                                                  (undeveloped               Table 1.
                                                                                                  area)                      Sununary of
                   Beach nourishment              High                     Low to high            Medium to high             shore-
                   Revetments                     Low                      High                   Medium to high             protection
                   Seawalls                       Low                      High                   High                       alternatives.
                   Groins                         High                     Low to medium          Low to medium
                   Detached breakwaters           Medium to high           Low to medium          Medium to high
                     ixe
                   Detached breakwaters           Medium                   Low                    Low to medium
                   (floating)
                                                                                                                        _J


                                                                                                                                       97







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                              Conference, American Society of Civil                 Research, Special Issue No. 4, The Effects of
                              Engineers, 2144-2158.                                 Seawalls on the Beach, 29-39.
                           Richardson, T.W. 199 1. Sand bypassing, in:           Williams, S.J., Dodd, K., and Gohn, K.K. 1991.
                              Herbich, J. B. (Editor), Handbook of Coastal          Coasts in crisis, U.S. Geological Survey 1075,
                              and Ocean Engineering, Vol. 2, Gulf Pub. Co.,         32 pp.
                              Houston, Texas, 808-828.

































                           100






                 A DISCUSSION OF "SHORE PROTECTION AND                                                                                ENGINEERING
                 ENGINEERING WITH SPECIAL REFERENCE                                                                                    -------
                 TO THE OREGON COAST

                 Spencer M. Rogers, Jr.
                 Department of Civil Engineering, North Carolina State University, and
                 UNC Sea Grant Marine Advisory Service                                                                              SHORE
                                                                                                                                    PROTECTION
                                                                                                                                    AND
                                                                                                                                    ENGINEERING
                 Relocation, the first of the four general shor-e-pro-    to avoid the need for other shore-protection alter-
                 tection responses discussed in the previous paper,       natives. To be effective, the setbacks must be
                 by Kraus and McDougal, can be broadened to               large enough to protect the building for its entire
                 more clearly include planning and management             useful life. Given the uncertainties of long-term
                 options such as setback lines, which are discussed       erosion prediction, a significant safety factor (for
                 elsewhere in the paper. Relocation implies that          example, an increased setback distance) should
                 the facility was planned for a location sufficiently     be included. For a wood-frame house with a 70-
                 threatened by erosion to eventually require move-        year useful lifetime, a I 00-year erosion setback
                 ment to a less hazardous location. Avoidance is a        might be an appropriate minimum to effectively
                 broader category that can include initial siting de-     use avoidance for shore protection.
                 cisions to (1) avoid the hazard for the useful life         For a variety of practical and political reasons,
                 of the facility, (2) avoid the hazard for a planned      such large setbacks are not feasible on many
                 period, at which time relocation can be used to          shorelines with significant erosion rates. Reloca-
                 extend the functional life of the facility, or (3) re-   tion must therefore be anticipated when smaller
                 locate to avoid the hazard if there was no plan-         setbacks are used. For example, North Carolina's
                 ning or if the hazard was initially underestimated.      coastal management regulations require mini-
                    As discussed by the previous authors, design          mum oceanfront setbacks of 30 times the annual
                 lifetimes of 50 years are often used in building         erosion rate for small buildings and 60 times for
                 codes and coastal protection designs. However, a         large buildings. Congress is currently considering
                 design lifetime is often different from a useful         similar legislation as an amendment to the Na-
                 lifetime. For example, many buildings are de-            tional Flood hisurance Program. Small buildings
                 signed for 50-year wind speeds. After determin-          can be designed to be relatively easy to relocate.
                 ing the predicted forces, the designer adds a            A larger setback is imposed on larger buildings
                 safety factor to the forces before selecting proper      because of the greater engineering difficulty and
                 materials and sizes. The designer, at least for          the cost of relocation.
                 buildings, gives his or her assurance that the              Small buildings have been moved away from
                 building should withstand reasonably predicted           erosion threats routinely in North Carolina. To
                 conditions for at least 50 years. Because of the         date, no large buildings have been sufficiently
                 safety factors, the ultimate strength of the build-      threatened to justify moving. With a 60-year set-
                 ing can be expected to survive much worse                back and North Carolina's ban on stabilization
                 conditions.                                              structures, it is inevitable that the regulations will
                    One practical effect for buildings is that they       be tested by threatened large buildings in the
                 often last longer than a 50-year design life. The        future.
                 average useful lifetime of a wood-fmme house in             Minimum erosion-based setback lines clearly
                 the U.S. is about 70 years (Anderson 1978) and           force some development farther away from the
                 slightly longer for larger buildings or other con-       shoreline. But setbacks can have other less obvi-
                 struction materials.                                     ous and sometimes undesirable effects as well.
                    Either voluntary or regulatory setbacks based         Stutts, Siderelis, and Rogers (1985) looked at
                 on predicted erosion rates are clearly useful tools      property owner response to the first two years of


                                                                                                                                 101








                                                                I
                                                          MINIMUM SETBACK


                                                                I
                                                                t
                                                  40




                             NUMBER OF NEW
              Figure 1.            HOUSES         30
                                                                                                             AVERAGE USEFUL LIFE
                                                                                                                    OF A
                                                                                                                 RESIDENCE



                                                  20


                                                  10                                                                      TOTAL:87
                                                                  40    8      16  6 r5       3     3   @31                  F 2-1
                                                                30          40       30          60        70         so         90

                                                               TIME OF SAFETY FROM LONG-TERM EROSION (YEARS)



                           the 30-year setback in four North Carolina com-         appropriate safety factors, a 50-year wind design,
                           mw-fties. By measuring the actual distance own-         compares well with the 70-year average useful
                           ers chose as a setback and dividing by the annual       lifetime of a house. The 30-year erosion setback
                           erosion rate, the researchers determined the rela-      is far less than the useful life. Property owners
                           tive level of erosion safety for each new building.     appear to reason that "If the regulations allow us
                           Thirty percent of the owners chose to build as          to build this close to the ocean, it must be safe,"
                           close as possible on the 30-year minimum. Half          rather than "If located here, the building will fall
                           the owners chose to build with fewer than 35            in the ocean in 30 years." Regardless of the edu-
                           years of erosion safety, as shown in figure 1.          cational efforts of the regulators, the minimum
                           Only 3 percent located with erosion safety levels       seems to become the norm.
                           greater than 70 years. In some cases the property          Use of a minimum setback when there is room
                           lacked sufficient depth to locate farther landward.     farther landward on the property can cause prob-
                           But where room was available, three-quarters of         lems even for owners committed to avoidance or
                           the owners chose to use more of the extra build-        relocation. On property lacking unlimited depth
                           able depth to build farther away from the street        for relocation, leaving smaller distances on the
                           setback than from the ocean setback.                    landward side of the building may make it
                              Many factors, including the perceived threat         unfeasible to use the area when relocation is
                           of erosion, influence the decision on where to,         eventually needed. Initial construction as far
                           locate development on a specific property. One          landward as possible might provide an additional
                           of the undesirable effects of establishing regu-        5 or 10 years of use beyond the minimum
                           lated setbacks significantly less than the useful       setback location. But once a building is con-
                           life of the building is that some owners will be        structed at the minimum, the owner cannot jus-
                           encouraged to build farther seaward. It is com-         tify the expense of relocating it the short distance
                           mon in many forms of regulation that when               to the back of the property. Relocation would
                           minimum standards are established, they become          then require purchase of another building site.
                           the standard, neglecting the minimum intent. If         When relocating a building, the owner usually
                           the level of the standard is high compared to the       must comply with the erosion setbacks at the
                           useful life of the action, there are few problems.      time of the move. By the time relocation is nec-
                           For example, a I 00-year flood design or, with          essary, erosion can move the minimum setback


                           102







                far enough inland to prohibit relocation on the          particularly in small buildings, can be considered
                same lot even if the owner wishes to relocate            avoidance of waves. Typical designs incorporate
                there.                                                   open piling foundations above any anticipated
                  The use of erosion setbacks significantly              wave action and enough piling penetration to tol-
                smaller than the lifetime of the development is          erate any wave-induced erosion.
                often a political reality, given the shallow build-         In summary, avoidance using erosion-based
                able depth available along much of the subdi-            setbacks can be a useful tool for shore protection.
                vided shoreline and given the desire to avoid            However, the use of setbacks with shorter life-
                legal challenges on the taking issue. To make the        times than the useful lifetime of the development
                best use of avoidance or relocation regulations, it      is often misunderstood by owners and may en-
                is more effective to require setbacks comparable         courage some to locate as far seaward as the
                to the lifetime of the development, but, if neces-       minimum setback will allow. For avoidance to be
                sary, to make exceptions that allow owners to            effective, owners must truly understand the ero-
                build farther seaward when the building is               sion hazard and have a plan for relocating when
                planned as far landward as the property will             necessary. At locations where smaller setbacks
                allow.                                                   must be applied, it is better to use the maximum
                   Avoidance can be broadly interpreted to in-           feasible setback and thus use the assets of the
                clude the use of appropriate construction tech-          property to best advantage.
                niques that are not explicitly addressed in the four
                possible shore-protection responses. Erosion-            References
                based setbacks are not effective in preventing
                damage to coastal buildings during infrequent but        Anderson, C.M. 1978. Coastal residential struc-
                extreme storm events, particularly in areas with            tures life term determination. National Asso-
                low long-term erosion or on low ground eleva-               ciation of Home Builders Research
                tions likely to be overtopped by storm conditions           Foundation, Inc., Rockville, Maryland.
                (Rogers 1990). For example, without stringent            Rogers, S.M., Jr., 1990. Designing for storm and
                construction standards, there is no safe place to           wave damage in coastal buildings. Proceedings
                build on spits or barriers. However, in such cases          for the Coastal Engineering Conference.
                properly designed methods for building construc-            American Society of Civil Engineers, pp.
                tion or other shore-protection options can be               2908-2921.
                effective.                                               Stutts, A.T., Siderelis, C.D., and Rogers, S.M., Jr.
                   Extreme storm events cause waves, storm                  1985. Effect of ocean setback standards on the
                tides, and erosion at locations well inland from            location of permanent structures. Proceedings
                areas of normal shoreline fluctuations. The nor-            of Coastal Zone '85, American Society of
                mal design philosophy for extreme events,                   Civil Engineers, pp. 2459-2467.












                                                                                                                             103





        PUBLIC POLICY RESPONDING TO 0REGON9S SHORELINE
                            EROSION HAZARDS: SOME LESSONS
                    Lot     LEARNED FROM CALIFORNIA
                     2

        Z
                   3 ..'    Gary B. Griggs
                            Institute ofMarine Sciences, University of California, Santa Cruz
        SHORE
        PROTECTION
        AND
        ENGINEERING         Introduction                                           to the hazards of shoreline erosion, wave impact,
                            The geological hazards along the coastlines of         and inundation. Although progress has been
                            California and Oregon are similar in many re-          made in reducing both public and private expo-
                            spects. Earthquakes and tsunamis represent large-      sure to coastal hazards in California over the past
                            scale threats that occur relatively infrequently.      several decades, particularly since the passage of
                            Bluff failure, shoreline erosion, and storm wave       the Califomia Coastal Initiative in 1972, major
                            inundation, on the other hand, produce less over-      problems remain. Serious policy gaps exist in the
                            all damage per event, but are more frequent oc-        State Coastal Act. State agencies continue to fund
                            currences. One major difference between the two        or undertake questionable coastal protection
                                                                                   projects. Wide variation in interpretation and
                            states is that California has 10 times as many         implementation of the Coastal Act by local gov-
                            people (1990 census of just over 30,000,000) and       ernments raises important questions regarding the
                            that the oceanfront area of southern and much of       actual level of coastal resource protection
                            central Califorriia has been intensively developed     achieved under current state policies.
                            (figure 1). The Oregon coast, in contrast, has            At the time the Coastal Initiative was passed
                            been, until recently, relatively undeveloped, al-      by the California voters, it was widely acknowl-
                            though this has slowly begun to change.                edged that local governments, acting incremen-
                              The goal of all of those involved with coastal       tally and in isolation from each other, could not
                            geologic hazards should be to reduce the number        adequately address the various problems occur-
                            of people, as well as dwellings, structures, and       ring along the state's ocean shoreline. It was this
                            utilities, both public and private, directly exposed   very fact that led to the creation of the California

                                                                                                     41F




                                                                                                                         ,A:


                            Figure 1.                                                                    X"a
                                                                           Nis
                            Oceanfront home
                            development along
                            the cliff and beach
                            of southern
                            California near
                            Malibu.














                            104







               Coastal Zone Conservation Commission and its            or redwood deck has been undercut by waves
               mandate to prepare a statewide plan for the per-        (figure 2). Many oceanfront residents have dis-
               manent protection of the remaining natural and          covered too late that sliding glass doors and half-
               scenic resources of the coastline.                      inch thick plywood siding are no match for the
                  California's coastal hazards and its policies        large driftwood logs thrown about by the surf
               relating to coastal hazards and hazard protection       crashing through their front yards.
               have been the subjects of considerable recent re-          Two areas of major concern that need to be
               search (Griggs et al. 1991; Griggs and Fulton-          addressed are the particular site itself and the
               Bennett 1988; Griggs 1987a; Fulton-Bennett and          structure, either existing or proposed. Consider-
               Griggs 1986; Griggs and Savoy 1985). It is be-          ing both the hazards that affect coastal areas and
               lieved that the experience gained from California       the very high cost of oceanfront property, anyone
               should be of value to coastal hazard geologists,        contemplating such an investment is strongly ad-
               coastal engineers, and coastal planners in              vised to hire a professional with experience in the
               Oregon.                                                 coastal zone to evaluate the stability of the prop-
                                                                       erty and its structures. Along the California coast
               Hazardous Coastal Environments                          there are dime particular physical envirorunents
                                                                       where widespread development has taken place
                  The coastline is a dynamic and ever-changing         but that are potentially hazardous. These same
               environment. Changes occur both over short time         environments occur along the coast of Oregon.
               intervals (for example, the changes from a single       They are (1) the beach, (2) the dunes, and (3)
               storm) and over longer intervals (the progressive       eroding cliffs or unstable bluff tops.
               erosion of a particular unstable bluff area over a
               number of years, for example). Both types of            Identifying Coastal Hazards
               changes can affect a property or building, and
               individuals should seriously evaluate both before          With any oceanfront area or environment,
               investing their life savings. The wide protective       there are two different situations to consider-
               surnmer beach can disappear quickly during a            undeveloped property and developed property.
               major storm, and before long the concrete patio         With undeveloped property, the opportunity








                                                                                                          Figure 2. Beach
                                                                                                          levels have been
                                                                                                          lowered
                                      T     '7'
                                                                                                          approximatelv five
                                                                                                          feet due to a
                                                                                                          combination of high
                                                                                                          tides and storm
                                                                                                          waves to undercut
                                                                                                          this deck and
                                                                                                          exposefoundations
                                                                                                          in northern
                                                                                                          Monterey Bay,
                                            V
                                                                                                          California.
                                         k.;
                           1 Jji





                                                                                                                             105





                              exists to carefully evaluate the hazards, both short      Responses to Coastal Hazards
                              and long term, and the risks they pose prior to any
                              development of the land. In California, the nature            Over the past 50 years, the principal response
                              and the scope of the site investigation that is re-       to coastal hazards in California has been the con-
                              quired prior to approval of any oceanfront devel-         struction of strucWms-seawalls and rip-rap re-
                              opment are legislated by local governments,               vetments for the most part-designed to protect
                              although in principle, these are, over time, sup-         eroding or wave-affected shorelines. Protective
                              posed to come into confonnance with the State             devices have usually been constructed only after
                              Coastal Act. In a detailed investigation of state         existing shoreline development have become at
                              coastal hazard policies in California (Griggs et a].      risk. Rarely in the past did such a protection strat-
                              199 1), it became clear that the 15 counties and 35       egy precede development. At present, however,
                              cities had established very different requirements,       some of Califori-iia's coastal municipalities re-
                              standards, policies, and practices, as a result of        quire a protective structure as a condition for de-
                              the paucity of state coastal hazards policy and the       velopment of oceanfront property. In striking
                              considerable ambiguity and latitude of applicable         contrast, other communities will not allow devel-
                              state guidelines. As a result there is a wide variety     opment in locations where a protective device
                              of approaches to coastal natural hazards among            would be necessary in order to insure the survival
                              local governments as well as state agencies.              of the property fl-irough the design life of the
                                 Nonetheless, with adequate and competent site          structure.
                              investigation, the hazards and risks posed by geo-           In recent years, the growing recognition of the
                              logic processes to any oceanfront parcel, whether         limitations and impacts of "hard" protective
                              it be beach, dune, or bluff, can be identified,           structures or annor has led to the consideration
                              evaluated, and incorporated into the plannig pro-         and implementation of "soft" approaches, such as
                              cess. With adequate safeguards, which may in-             beach nourishment. Moreover, the high capital
                              clude a range of approaches, including setbacks,          and maintenance costs of protective structures
                              engineered foundations, elevating, runoff, and            have led to the economic justification of physi-
                              groundwater control, or complete relocation,              cally relocating structures away from hazardous
                              these risks can be reduced to an acceptable level.        areas (Griggs 1986).
                              In this way, we can eliminate the need for a              Development Relocation
                              coastal protection structure or an emergency re-             Relocation of oceanfront structures or utilities
                              sponse in the future. This is clearly the favored         is being given increasing consideration in a num-
                              approach and would result in the lowest long-             ber of situations. Where a parcel is large enough,
                              term public and private costs. In California, over        a threatened structure can be moved landward on
                              the past decade, the losses and costs of shoreline        the same property to extend the period of protec-
                              protection, storm damage, and other expenses re-          tion, depending on the erosion rates. In many
                              lated to oceanfront development have averaged             cases this will not be possible, and relocation will
                              nearly $ 100 million annually. These are losses           require acquisition of a separate lot. Recent com-
                              and expenses that Oregon can avoid with careful           parisons of the cost of relocation or reconstruc-
                              siting of any new development, whether public or          tion and the cost of protection have indicated that
                              private.                                                  in the long run, relocation may be far less expen-
                                 In contrast to undeveloped land are those prop-        sive (Griggs 1986). Typical house-moving costs
                              erties which are already developed in potentially         for a moderate-sized residential structure may be
                              hazardous oceanfront locations. A careful look at         in the range of $10,000 to $25,000, whereas con-
                              the Oregon coast will make it clear that, even            struction and maintenance of a protective seawall
                              with a relatively undeveloped shoreline, there are        may be several or up to 10 times as high over the
                              a number of old and also recent examples where            life of the residence. It is likely that this option
                              the hazardous nature of the site either was not           has not been seriously considered by most thi-eat-
                              recognized or was disregarded in the siting of de-        ened oceanfront property owners, simply because
                              velopment.                                                of the desire to protect their home and view at


                              106







                   any cost. Some coastal communities have begun                     day , 365 days a year, would have to arrive every
                   to require that shorefront homes be designed and                  17 minutes. The economics of a large-scale beach
                   built in such a manner that they can be easily re-                nourishment effort and the distribution of costs
                   located or moved in the future, thus reducing the                 also pose major questions for this approach to
                   cost of this approach.                                            coastal protection.
                   Beach Nourishment                                                    The most accepted view at present is that Or-
                      Nourishment, or beach replenishment, has                       egon beaches are parts of individual littoral cells
                   emerged as an appealing "soft" approach to deal-                  trapped between major volcanic headlands, and
                   ing with the problems of shoreline erosion. On                    that little littoral transport or exchange of sand
                                                                                     takes place between cells. If this is true then re-
                   the surface this strategy presents an attractive
                   compromise to the extremes of abandoning the                      plelushing sand might be a more reasonable ap-
                   shoreline on the one hand, or armoring it with                    proach in Oregon, where sand would have a
                   concrete or rock on the other. The beach is nour-                 longer lifespan, than on California beaches, with
                   ished or replenished with sand from either an off-                their high rate of littoral drift. Sand presumably
                   shore or inland source. The goal is to increase the               continues to reach the shoreline today from river
                                                                                     and cliff sources, yet the beaches are not growing
                   width of the beach such that it serves as a more                  wider. There are clearly sinks for this littoral
                   effective buffer and protects the shoreline from                  sand, and these sinks (whether onshore or off-
                   wave attack, thereby reducing erosion.                            shore) need to be carefully studied and the rates
                       While in theory beach nourishment represents                  of loss quantified to the degree possible, prior to
                   a more "natural" approach to the problem o                        considering nourishment as a solution to
                   shoreline erosion, there are many considerations                  Oregon's shoreline erosion problems.
                   that owners must address before embarking on
                   any large-scale nourishment project (Leonard et                   Armoring or Hard Protection Structures
                   al. 1989). Availability of large volumes of sand of                   Historically, the most common approach to
                   the appropriate grain size is one of the first issues             protecting private or public structures or utilities
                   to be resolved, as is the impact of sand removal                  from coastal erosion has been the construction of
                   and transport. In order to add a volume of sand to                some type of "hard" protection structure. In Cali-
                   a beach equivalent to a typical California annual                 fornia, as of 1990, 130 miles, or 12% of the entire
                   littoral drift rate of 300,000 cubic yards, a 10-cu-              shoreline, had been armored or protected by some
                   bic-yard dump truck delivering sand 24 hours a                    f6im of hard protective structure (figure 3).







                                                                                                                                  Figure 3.
                                                                                                                                  The construction
                                                                                                                                  of continuous
                                                                                                                                  seawalls has
                                                                                                                                  taken place al the
                                                                                                                                  base of this devel-
                                                                                                                                  oped southern
                                                                                                                                  California bluff.


                                                                                        Z
                                                                                  5,
                                                                                          -,"Mc
                                                                                                           21
                                                                                                           ........................................ . . . . . . . .













                                                                                                                                                    107







                            Protective structures can vary considerably in           During exceptional high tide and storm wave
                            cost, size, effectiveness, and life span (Fulton-        conditions, such as those during the El Nifto of
                            Bennett and Griggs 1986). At one extreme, slabs          the 1982-83 winter, protective structures which
                            of broken concrete or asphalt or other construc-         have survived for decades may fail virtually over-
                            tion materials have simply been dumped at the            night. Some protective structures have fared far
                            base of cliffs in an attempt to reduce the impact        better than others. Our research in Califorriia. indi-
                            of waves. Most efforts of this sort have been rela-      cates that for most types of structures, there are a
                            tively futile or very short lived. At the other ex-      number of precautions, alterations, or design cri-
                            treme are massive, carefully engineered and              teria which, if used, can significantly improve the
                            expensive concrete seawalls, which may stand for         structure's effectiveness or extend its lifespan.
                            30 or 40 years or more (figure 4). What should be        Concrete Rubble
                            made clear at the onset, however, is that on a rap-         Broken concrete and other construction debris
                            idly eroding shoreline, any protective structure         are some of the oldest and cheapest, but least ef-
                            built to withstand direct wave attack will prob-         fective, materials that have been dumped over
                            ably fail eventually. Even a well-designed struc-        seacliffs and onto beaches with the intent of pro-
                            ture is likely to fail once its design life has been     tecting coastal property. These materials gener-
                            exceeded, especially if it has not been properly         ally consist of loose dirt, flat concrete or asphalt
                            maintained. Engineers commonly think in terms            slabs of various sizes, or small stones or bricks.
                            of a 20- to 25-year life of a coastal protection         At some places, concrete slurry has been added to
                            structure. This should be clearly understood by
                            the homeowner, but often is not.                         the debris, increasing its strength but not neces-
                               Spending large amounts of money on the in-            sarily its stability.
                            stallation of a coastal engineering structure does          Because rubble is often used during emer-
                            not guarantee long-tenn, or in some cases, even          gency situations and is seldom engineered, its
                            short-term, protection for home and property. The        costs are difficult to determine. Since the material
                            exposure of a property to wave attack, the pres-         is usually free and is often simply dumped at the
                            ence and width of a protective beach, and the spe-       shoreline, its cost depends primarily on the price
                            cific design, construction, and dimensions of the        of hauling the material to the site. However, ex-
                            structure will all influence its effectiveness,          cept during low wave conditions, or where very








                                                                                                                          -io    0
                            Figure 4.
                            Construction of a
                            curved-face
                                                                                                                                    J
                            concrete seawall
                            near Santa Cruz at
                            a cost Of
                            approximately
                            $30001frotafoot.






                                                                                     7

                                                                      AO




                            108







               large volumes are used, the benefits of this type        the toe of the structure. Such seaward movement
               of "protection" are also very low. It fact, the use      is the result of a gradual or rapid undermining of
               of concrete rubble may generate unexpected               the toe stones, which causes them to rotate sea-
               costs, first because it gives the appearance of pro-     ward (figure 5). The rate and amount of riprap
               tection, leading to a false sense of security and        settling vary considerably from one location to
               greater investment in endangered property, and           another. Often, comers, end sections, and other
               second, because it must often be removed before          localized segments of a single wall will settle,
               any engineered structure can be built at the site.       while the rest of the wall remains more or less
               Its use as a core stone in riprap walls is also of       intact.
               questionable value, unless its size and shape can           The second common failure mode for riprap
               be carefully controlled. Even then, it may be eas-       has been described as sliding, toppling, rolling, or
               ily displaced or removed, when the armor rock            plucking, and occurs when waves mobilize one or
               shifts or settles.                                       more armor stones in a wall, allowing them to
               Riprap                                                   move down to a new position of temporary stabil-
                  Riprap revetments (engineered and nonengi-            ity. To prevent this type of failure, Moffat and
               neered) are by far the most common structures            Nichols (1983) recommend avoiding smooth,
               used for protecting coastal property along the           rounded, elongate, or flattened stones, and care-
               California coast. In this paper, riprap is used as a     fully placing rocks so that they interlock with one
               general term, referring to any large (usually I- to      another and do not protrude from the face of the
               5-ton) rocks used for coastal protection. Until the      structure more than 18 inches. The Shore Protec-
               late 1970s, such rocks were often just durnped           tion Manual (U.S. Army Corps of Engineers
               over seacliffs or on top of the sand in front of         1977) recommends that all riprap subject to
               endangered coastal property. This practice is still      breaking waves be stacked at a slope no steeper
               common during emergency situations. The re-              than 1.5:1 (1.5 horizontal to I vertical, or 35 de-
               sulting structures are usually referred to as rubble     grees). Although a steeper wall will encroach less
               revetments or riprap seawalls, or as nonengi-            far onto the beach and initially will require less
               neered riprap. Engineered riprap, in contrast,           rock, such a wall is much more prone to toppling
               incorporates a carefully excavated foundation or         or plucking and subsequent collapse.
               keyway, filter cloth, and carefully placed layers           From an evaluation of a large number of riprap
               of different sizes of rock. It has been used and         revetments along the central California coast, a
               required with increasing frequency over the past         number of conclusions have been reached
               decade. Engineered riprap is normally designed           (Fulton-Bennett and Griggs 1986):
                                                                           1) Riprap revetments do not always exhibit the
               according to explicit assumptions regarding storm        ,flexibility" portrayed in some engineering publi-
               waves, scour depths, and water levels. Although          cations. histead of settling as a cohesive unit, in-
               nonengineered riprap is more likely to be struc-         dividual stones tend to separate as they rotate or
               turally damaged over time, both types can be             settle, often moving seaward in the process
               susceptible to the same types of failure during          (figure 5).
               storms.                                                     2) Riprap walls may fail quite rapidly, often
                  In general, along the central California coast,       leaving behind gaps or arcuate, landslidelike
               we observed that the success rate of riprap walls        scarps of oversteepened riprap or exposed fill.
               is marred by relatively high repair and mainte-          Because many walls are designed as low as pos-
               nance requirements and by the fact that signifi-         sible to minimize costs, even minor settling can
               cant property damage often occurs when these             allow significant overtopping, erosion, and dam-
               walls suffer even partial failure (Fulton-Bennett        age behind the wall.
               and Griggs 1985). At virtually every location               3) Riprap revetments built over steep, loosely
               where riprap has been founded on sand, in con-           consolidated materials require carefully planned
               trast to a bedrock foundation, it has settled into       drainage systems to avoid erosion of material be-
               that sand over time. This settlement is often ac-        hind the rock. Numerous riprap walls were out-
               companied by a seaward movement of rocks at


                                                                                                                              109










                                                                                                          face stone 1.5   1 slooe

                                                                                                          core stone                                        initial toe configuration

                                                                                                          filter cloth                                        summer beach level

                                                                                                            ................                               minimum winter beach
                                                                                                                                 ... .............
                                                                                                                                                     . ................
                                                                                                                                                                              MSL

                                                                                                                                                                          ..............


                                                                                                          theoretical configuration of toe after beach scour








                                                                                                                                        face stone unsupported
                                     Figure 5. Failure ol a                                                                             core stone exposed to direct wave attack
                                     riprap revetment due
                                     to scour at the toe.



                                                                                                                                        MSL
                                                                                                                               . . . . . .   . . . . . .
                                                                                                                                        toe stones rotate, settle and move seaward









                                                                                                          erosion of bluff by wave overtopping

                                                                                                          filter cloth torn and tattered



                                                                                                          erosion of fill from beneath revetment
                                                                       - - - - - -                        final, concave-upward profile
                                                                                                                                                                              MSL



                                                                                                                                         (Z)



                                     flanked or partially failed because of erosion from                        6) Where maintained and founded on bedrock,
                                     uncontrolled runoff flowing behind or around                           riprap has proven relatively effective in slowing
                                     them.                                                                  erosion, but maintenance costs, even for engi-
                                        4) Although placing new rocks on top of old,                        neered ripr-ap, are usually quite high. The total
                                     settled ones is relatively simple, repairing an old                    amount of rock required in California today to
                                     riprap wall while it is being overwashed during a                      protect a single ocean-front lot ranges from 500
                                     storm is extremely difficult and dangerous. At                         to 2000 tons, or approximately 10 to 25 tons per
                                     many sites, access is impossible under these                           foot of ocean frontage. At average prices of $35
                                     conditions.                                                            to $45 or more per ton, these walls can cost
                                        5) Although a riprap wall absorbs more wave                         $25,000 to $100,000. However, after a storm of
                                     energy than do impen-neable seawalls, it does                          roughly 10-year recun-ence interval, engineered
                                     have a sloping seaward face. Because not all of                        structures along the central California coast re-
                                     the wave energy is absorbed under high tide and                        quired repairs totalling 20% to 40% of their con-
                                     storm wave conditions, waves running up and                            struction costs, and nonengineered structures
                                     overtopping a riprap revetment can damage                              required repairs totalling between 50% and 150%
                                     houses (figure 6) or erode fill behind the riprap.                     of construction costs.




                                     110








                 Concrete Seawalls
                     Concrete seawalls are con-                                                                             v
                 tinuous, rigid structures whose
                 vertical or concave faces reflect
                                                                                                                                                Figure 6. Damage to
                 wave energy upward, down-                                                                                                      oceanfront homes
                                                                                                                                                due to high tides and
                 ward, and back out to sea.
                                                                                                                                                storm waves over-
                     There are three major types                                                                                                topping a riprap
                 of concrete seawalls: gravity
                                                                                                                                                revelment during the
                 walls, self-supported structures                                                                                               winter of 1983 along
                 which balance anticipated hori-                                                                                                the central California
                                                                                                                                                coast.
                 zontal forces by their sheer                      All
                 mass; cantilevered walls, which
                                                                @4
                 rely on support from a deep                                                                     Lk'
                                        -back wall
                 foundation; and tie                S,
                 which are braced by cables or
                 rods tied to anchors in the fill behind them. The              concentration of flow at small openings, and the
                 U.S. Army Corps of Engineers (198 1) lists the                 resulting fluid velocities are great enough to
                 following as typical causes of failure for concrete            erode granular material. Where drains or weep
                 seawalls fronting the Great Lakes:                             holes have been included within a seawall to al-
                     a) loss of foundation support                              low for drainage from behind the wall, or where
                     b) inadequate penetration                                  partially open joints exist between panels, it is
                     c) scour at toe                                            critical that a system be used that prevents piping
                     d) outflanking                                             of sand or fill through these openings. Some com-
                     e) inadequate height                                       bination of graded rock or gravel fill and filter
                                                                                cloth as well as perforated caps or plugs over the
                     These causes of failure are also typical for               weep holes is strongly recommended in order to
                 west coast walls. Loss of fill and, therefore, sup-            minimize or eliminate piping under conditions of
                 port behind walls due to piping (the subsurface                severe wave surge and overtopping.
                 removal of loose sediment, soil, sand, or fill,                    Concrete walls, in general, have proved to be
                 caused by water flowing through holes or voids),               the most durable type of protection along the cen-
                 gullying, or undermining are also prevalent.                   tral California coast. Although their initial costs
                     Scour or undermining at the toe of a concrete              may be somewhat higher than riprap and wooden
                 seawall has been a common concern and has led                  walls, if they are well designed, their maintenance
                 to the loss of foundation support for a number of              costs may be relatively low. Along the central
                 walls in the past. This has been a problem for                 California coast typical concrete seawall costs
                 walls founded on either sand or bedrock at the                 have ranged from $750 to almost $3000 per lin-
                 time the material is either eroded or removed.                 ear foot.
                 Most concrete walls studied in central California                  The relatively high costs of well-engineered
                 (Fulton-Bennett and Griggs 1975) toppled sea-                  concrete seawalls, which extend both high
                 ward when they failed, because of erosion Of sand              enough to prevent significant overtopping and
                 or bedrock at their toes, or the active pressures Of           deep enough so that they are not undermined by
                 fill and water behind them.                                    scour, have almost eliminated this type of struc-
                     Concrete seawalls built on sandy beaches lost              ture from consideration by the individual
                 fill both from underneath when sand levels                     homeowner. In some cases where public services,
                 dropped and from behind the wall by piping. This               such as streets and utility lines, are involved,
                 piping takes place after fill behind the wall be-              homeowner groups and assessment districts have
                 comes saturated by wave splash, spray, and in                  cooperated with public agencies to finance and
                 some cases, groundwater. Under such saturated                  build projects of this sort. It is important to stress
                 conditions, piping occurs because of the                       here the need for a continuous coherent wall or


                                                                                                                                             III







                                 approach in contrast to individual homeowners'                  most common design along the central Califon-da
                                 building a series of different types of walls. In               coast incorporates vertical wooden pilings six to
                                 such a situation, the entire structure is only as               eight feet apart, embedded in the sand with hori-
                                 strong as the weakest link. Once an individual                  zontal boards (called lagging), usually 3 x 12 to 6
                                 segment of a seawall is damaged or destroyed                    x 12 inches in cross-section, nailed or bolted to
                                 and the supporting fill begins to be removed from               the landward side of the pilings. In the last de-
                                 behind the wall, then the integrity of the entire               cade, such walls have also incorporated filter
                                 structure is threatened.                                        cloth behind the horizontal wood planks, and of-
                                    The two most critical problems observed in                   ten tiebacks into the fill behind the wall.
                                 concrete seawall design are preventing loss of fill                Even chemically treated wooden walls tend to
                                 from behind, around, and underneath the wall and                decay and deteriorate with exposure to salt water.
                                 maintaining the wall's stability and rigidity if                No matter how well designed, most wooden walls
                                 such loss does occur (figure 7; Fulton-Bennett                  will usually decay after 10 to 20 years in the surf
                                 and Griggs 1985). Concrete walls incorporating                  zone. Wooden walls are also highly vulnerable to
                                 deep (at least 8 to 10 feet below MLLW), inter-                 battering by floating logs and debris, which is
                                 locking sheet piles or panels have generally been               common along the northern California and Or-
                                 successful in sandy areas; walls based on indi-                 egon coasts (Griggs 1987b). Riprap placed in
                                 vidual pilings and those founded in exposed bed-                front of a wooden wall may reduce this problem
                                 rock have proven less durable. The latter two                   at low tide or under moderate wave conditions,
                                 types have tended to lose fill or foundation sup-               but this battering problem has proven to be a dif-
                                 pon from underneath, as the sand or bedrock is                  ficult one to avoid under severe wave attack (fig-
                                 removed by wave action.                                         ures 8 and 9).
                                                                                                                          Damage to many wooden
                                                                                                                       walls has been initiated when
                                                                                                                       floating debris (typically large
      Figure 7. Loss offill                                                                                            logs) cracked or broke horizon-
      behind upper portion                                                                                             tal planks or the pilings them-
      of seawall due to
      piping through weep                                                                                              selves, allowing fill to be
                                                                                                                       remo                    ints (figure
      holes. Storm wave                                                                                                      ved at these po
      impact against
      unsupported wall led       4,                                                                                    10), despite the presence of fil-
      to cracking and                                                                                                  ter cloth. Piping has also been a
      failure of portionws of                                                                                          problem when timber walls are
      thisjust completed,
                                                                                                                       overtopped
                                                                                                                                      Once the fill begins
      thin concrete
                                                                                                                       to erode from behind a wooden
      seawall.
                                                                                                                       wall, the uppermost planks am
                                                                                                                       almost inunediately separated
                                                                                                                       from the pilings by waves, ei-
                                                                                                                       ther because bolts or nails are
                                 Wooden Seawalls                                                 pulled out, or (more commonly) the boards are
                                   Wooden seawalls are used for purposes similar                 splintered by wave forces. This allows additional
                                 to concrete seawalls and may behave as bulk-                    overtopping to erode fill on either side of the
                                 heads, holding back fill materials. They also suf-              damaged area, causing gullying behind the wall
                                 fer many of the same problems of overtopping                    (figure 11). However, where wooden walls are
                                 and undermining. They are typically cheaper to                  fronted by riprap, even though some fill may
                                 install than concrete, however, which probably                  erode, the planks often stay in place at levels be-
                                 accounts for their continued use.                               low the top of the riprap. One significant im-
                                   Numerous designs for wood walls have been                     provement in the construction of timber seawalls
                                 tried over the years, including the use of railroad             in recent years at some sites has been the use of
                                 ties and steel H-piles as vertical supports. The                Epoxy-coated steel H-piles (which constrain the


                                 112

















                                                                                                                  Figure 8. Storm waves
                                                                                                                  carrying logs and debris
                                                                                                                  overtopping a low wooden
                                                                                                                  seawall in northern
                                                                                                                  Monterey Bay during the
                                                                                                                  winter of 1983.

                                                                                  7@
                                                                  j










                                                 4,,




                lagging, in contrast to simply
                using wood piles) and 6-inch-
                thick timber lagging. Walls of                                                                                   Figure 9. Wooden
                                                                                                                                 seawallfromfigure
                this construction have proved to                                                                                 8jollowing storm
                be far more able to withstand
                                                                                                                                 wave attack.
                the wave and debris impact than                                                                                I Approxi-mately 700
                                                                                                                                 feet ofseawall was
                the piling walls.
                                                                                                                                 destroyed as the
                                                                                                                                 lagging was
                                                                                                                                 battered by logs and
                Discussion                                                                                                       fill was lost. This
                                                                                                                                 $1.5 million wall
                   All shoreline protection                                                                                      had been corWIeted
                structures must be engineered                                                                                    just two months
                                                                                                                                 before.
                and built to withstand four basic
                types of wave effects: over-
                topping, undermining, out-
                flanking, and impact.                                    consider only the frequency of overtopping by
                   Overtopping is defined as the transport of sig-       green water. The height of this run-up is usually
                nificant quantities of ocean water over the top of       calculated using empirical or theoretical formulae
                a seawall as green water, splash, or spray.              based on water depth, beach slope, significant
                Overtopping causes damage in several ways, by            wave height, wave period, and maximum ex-
                exerting direct vertical and horizontal forces and       pected sea level (which continues to change).
                by eroding material from behind walls. In most           Variabilities in the natural environment, however,
                coastal environments it is not practical to build a      can produce a wide range in the maximuni wave
                seawall that will not be overtopped during severe        run-up elevations calculated using this method.
                storm conditions. At many sites, cost is a limiting         Undermining of seawalls occurs when founda-
                factor. In addition, few coastal residents or cities     tion materials (usually sand, fill, or rock) are re-
                are willing to build seawalls which will sigi-dfi-       moved by wave action. This may take place not
                cantly block their view of the ocean. Standard           only when beach sand is scoured or fluidized, but
                nin-up calculations for seawalls typically               also where bedrock erodes rapidly during storms.


                                                                                                                            113







                                                                                              In either case, the result of undermining is of-
                                                                                              ten rapid loss of fill from behind a wall, and in
                                          fill (oite co.e,ed      itings                      some cases, structural failure. Predicting the
                                              with asphalt)      p
                                                                                              level to which a beach may be scoured is a dif-
                                                                                              ficult task. Coastal engineers have used a vari-
                                                                                              ety of "scour depths" in designing seawalls.
                                                    b ach         planks or tagging
                                                                                              Since there are no widely accepted formulas
                                                                                              for calculating these depths, estimates based
                                                                                              on field observations made during or (more
                                    A.  Initial summer conditions                             commonly) after storms are used. In areas
       Figure 10.                                                                             where bedrock is deep, borings are often used
       Progressivejailure                                                                     to determine the depth of storm lag deposits,
       of a wooden
                                                                                              consisting of gravel and cobbles. However,
       seawall through
                                                                                              several such layers may be encountered, and in
       overtopping and                 7.11
       loss offill.                                                                           the absence of accurate dating methods, the
                                                                                              selection of a design or expected scour depth
                                                                                              can be quite uncertain.
                                                                                                 The depth to which scour occurs will de-
                                    B. Overtopping by storm waves and failure of lagging      pend heavily on how far landward or seaward
                                                                                              a structure is located on the beach profile.
                                                                                              Within this zone, the depth of beach scour and
                                                                                              liquefaction should increase rapidly with in
                                     Al                                                       creasing distance seaward. Thus, there is an
                                                                                              inherent problem in any solution that involves
                                                                                              moving a structure seaward: the amount of en-
                                                                                              ergy it receives and the effects of that energy
                                                                                              will be greatly increased.
                                    C. Failure of wall and loss of fill                          Outflanking occurs when material to either
                                                                                              side of a seawall erodes to a point where it










                             Figure 11. Loss of
                                                                                                                                             r al.
                             fill behind a
                             wooden seawall
                             due to overtopping
                             and undermining.
















                             114







                threatens or damages the wall itself, or the prop-         in reducing erosion and property damage and
                erty behind it Along a progressively eroding               have been the most durable, over the long terin.
                coast, all successful, isolated protection structures      However, to survive, concrete walls supported on
                will be gradually outflanked because the coastline         discrete pilings have required moderate to high
                on either side will erode more rapidly than that           maintenance in the form of riprap toe protection.
                behind the wall. This is a relatively predictable          Riprap walls have fared less well than concrete
                process and should be planned for in the design            walls, but better than wooden walls. However,
                of any isolated wall in a rapidly eroding area.            their maintenance costs have often been much
                Most often, it is taken into account through the           higher than anticipated, particularly where placed
                use of wing walls running landward from the                on deep sand beaches. Wooden walls have
                ends of the main structure. However, because of            proven to be least successful in preventing ero-
                high costs and practical difficulties, such future         sion and damage, and most are easily damaged
                outflanking is usually ignored until it causes             by logs and debris during severe storms. Wooden
                property damage (figure 12).                               walls fronted entirely by riprap have been more
                   Often, outflanking of one wall leads to the             successful, as long as the riprap does not settle.
                construction of additional walls
                adjacent to the first. As the
                amount of continuously pro-
                tected coastline increases, out-
                flanking becomes a problem in
                                                                                                                                      Figure 12. Riprap
                the unprotected gaps. Nonethe-                                                  7
                                                                                                                                      has been outflanked,
                less, both for isolated walls and                                                                                     leading to erosion
                for gaps in protected coastlines,                                                                                     Of unprotected
                                                                                                                                      property as well as
                the question must be asked: Do                                                                                        bluff behind riprap.
                sea walls increase erosion in
                                                                                                    17.
                adjacent areas?
                   A recent four-year study
                along the central Califomia
                coast was directed at document-
                ing the effects of coastal protec-
                tion structures (seawalls and
                riprap revetments) on beaches (Griggs and Tait                On the whole, few protective structures along
                1988; Tait and Griggs 1990). A number of tem-              the central California coast have stood the long-
                porary or seasonal effects of seawalls on the              term tests of time, surviving unassisted and pre-
                fronting and adjacent beaches were documented              venting damage and erosion for more than 20
                in this field work. A zone of increased scour or           years or longer than their design life. Many stiuc-
                erosion was often observed downcoast from the              tures have become structurally unsound, required
                seawalls studied, and the extent of this erosion           considerable maintenance or repair, or failed to
                appeared to be related to several factors--the             adequately reduce property damage for more than
                configuration of the wing wall and its reflectivity,       one severe storm period. Thus, the effective life-
                the angle of wave approach, and the height and             time of a structure often depends on how many
                period of the waves. Waves were commonly ob-               mild winters pass before the next severe storm.
                served reflecting off the wing walls and were ca-          However, most of the structures have reduced
                pable in one case of producing increased scour up          erosion rates, at least over the short term.
                to 300 to 400 feet downcoast.                                 There are a number of options-some struc-
                                                                           tural, some nonstructural-available for people
                Conclusions                                                with threatened property. Before any protective
                                                                           structure is designed and built, its initial costs, its
                   Of the three major types of protection, con-            maintenance costs, its probable lifespan, its
                crete walls generally have been most successful            technical merits and limitations, and all of its

                                                                                                                                 115







                            potential impacts on the adjacent coastline need           existing land use policies and practices. In:
                            to be fully considered.                                    The California Coastal Experience, Am.Soc.
                                                                                       Civil.Engin.: 89-107.
                                                                                    Griggs, G.B. and Tait, J.F., 1988. The effects of
                            References                                                 coastal protection structures on beaches along
                            Fulton-Bennett, K.W., and Griggs, G.B., 1986.              northern Monterey Bay, Califon-da, Jour.
                                Coastal protection structures and their effec-         Coastal Research Spec. Issue No. 4: 93-111.
                                tiveness. Joint publication of the State of         Griggs, G.B. and Savoy, L.E., 1985. Living with
                                California, Department of Boating and Water-           the California coast. Duke University Press,
                                ways and the Institute of Marine Sciences,             Durham, NC.
                                University of Califon-da, Santa Cruz.               Leonard, L., Clayton, T., Dixon, K. and Pilkey,
                            Griggs, G.B., 1986. Relocation or reconstruction:          O.H. , 1989. U.S. beach replenishment experi-
                                viable approaches for structures in areas of           ence: a comparison of the Atlantic, Pacific,
                                high coastal erosion. Shore and Beach 54: 8-           and Gulf coasts. Proc. Coastal Zone '89,
                                16.                                                    Amer. Soc. Civil Engin.
                            Griggs, G.B., 1987a. Califomia's shoreline              Moffatt and Nichol, Engineers, 1983. Construc-
                                erosion: the state of the problem. Proc. Coastal       tion materials for coastal structures. U.S. Army
                                Zone '87, Seattle, WA., Am. Soc. Civil Engin.          Corps of Engineers,Coastal Engineering
                                pp. 1370-1383.                                         Research Center Special Report No. 10.
                            Griggs, G.B., 1987b. Failure of coastal protection Tait, J.F. and Griggs, G.B., 1990. Beach response
                                at Seacliff State Beach, Santa Cruz County,            to the presence of a seawall: a comparison of
                                California. Envir. Manag. 11: 175-182.                 observations, Shore and Beach 58:11-28.
                            Griggs, G.B., and Fulton-Bennett, K.W., 1988.           U.S. Army Corps of Engineers, 1977. Coastal
                                Rip rap revetments and seawalls and their              Engineering Research Center, Shore Protec-
                                effectiveness along the central coast of Califor-      tion Manual, V. I and 2, 3rd edition.
                                Wa, Shore and Beach 56:3-11.                        U.S. Army Corps of Engineers, 1981. Low Cost
                            Griggs, G.B., Pepper, J. and Jordan, M.E., 199 1.          Shore Protection-A Guide for Engineers and
                                California's coastal hazards: a critical look at       Contractors, Vicksburg, MS.























                            116






                 SHORE PROTECTION AND ENGINEERING: A                                                                               ENGINEERING
                 LOCAL PERSPECTIVE                                                                                                  -------

                                                                                                                                               Asp
                 Matt Spangler
                 Lincoln County Department ofPlanning and Development


                                                                                                                                  SHORE
                 Shore protection and engineering issues present a        context of structural and nonstructural techniques      PROTECTION
                 number of challenges for local planners and other        of protection, is a largely overlooked policy con-      AND
                                                                                                                                  ENGINEERING
                 regulatory officials. This brief discussion focuses      sideration.
                 on shore protection issues encountered in the con-         Kraus and McDougal go on to point out the
                 text of the local land use and regulatory process        importance of integrating the various options in
                 in the State of Oregon. Primary emphasis is on           shore protection techniques with the concept of
                 the identification of policy questions to be ad-         sand supply management on a littoral cell basis.
                 dressed in developing a comprehensive approach           While existing policy expresses preferences for
                 to shore protection management.                          nonstructural means of protection and attempts to
                                                                          limit the placement of hard structures, it fails to
                 Planning vs. Engineering                                 make any connection between these limitations
                                                                          and the objective of overall sand supply manage-
                   In their paper, Nicholas Kraus and William             ment within the littoral cell.
                 McDougal advance the principle of "plan region-
                 ally, engineer locally" as a key to proper manage-       Toward a Management System for
                 ment of shoe protection. Unfortunately, this
                 sound concept has seen little application in Or-         Shore Protection
                 egon. Shore protection projects are typically              The development of a coherent management
                 planned on a single-purpose basis, and current           system for shore protection must begin with a
                 policy and regulatory requirements neither re-           clear articulation of the goals and objectives of
                 quire nor encourage the integration of these             such a management system. While it is clear that
                 projects into a regional context.Ibe result is es-       known technical data on littoral cell dynamics
                 sentially no consideration of regional impacts (for      must be factored in to the development of any
                 example, the effects on a littoral cell) in the regu-    management objectives, perhaps a more impor-
                 latory review of individual projects.                    tant first step is the formulation of overall goals
                                                                          for the management of our public beaches. Only
                 The Relationship between Shore Reten-                    by knowing and clearly stating these goals can
                 tion and Backland Protection                             we appropriately use our technical knowledge as
                                                                          a base for devising a coherent management
                    Kraus and McDougal discuss the distinction            program.
                 between shore retention and backland protection,           Once an overall policy framework is estab-
                 separate concepts contained within the generic           lished, specific management priorities need to be
                 term "shore protection." Oregon shore protection         developed on a subregional (or littoral cell) basis.
                 efforts have focused almost exclusively on               Many factors, including existing development
                 backland protection primarily through various            patterns, will influence to what extent and with
                 structural means. Virtually no attention had been        which management tools the overall goals can be
                 paid to the role of beach stabilization in address-      achieved. By developing overall policy objectives
                 ing problems associated with shoreline recession.        and then formulating implementation strategies
                 The importance of an integrated approach to              on the local level, we can put into practice the ad-
                 shore protection, including consider-ation of both       monition to "plan regionally, engineer locally."
                 shore retention and backland protection in the



                                                                                                                                117



























                                                                                                                  .. . .. .....

                                                                                                                        VO,



           rN"












       27M





               RECENT LEGAL DEVELOPMENTS IN COASTAL                                                                             _PUBLK POLKY_
               NATURAL HAZARDS POLICY
                                                                                                                                 0
               Richard G. Hildreth                                                                                                           Lot
                                                                                                                                              2
               University of Oregon Ocean and Coastal Law Center
                                                                                                                                            3


                                                                                                                                COASTAL
               Introduction                                               Following are some examples of innovative             HAZARDS
                                                                       efforts to address coastal hazards (NOAA OCRM            POLICY ISSUES
               Coastal areas of the United States are affected by                                                               ON THE WEST
                                                                       1990).                                                   COAST
               a wide range of natural hazards that threaten lives        (1) North Carolina has established setback
               and property. Those hazards include severe              lines in areas of designated ocean hazard to pro-
               storms, floods, erosion, landslides, earthquakes,       tect buildings from coastal storms. The setback
               tsunamis, and subsidence. Over the past decade          lines will ensure at least 60 years of protection
               the problem of coastal hazards has become more          from coastal erosion for large structures and 30
               pressing. Americans continue to demand more             years of protection for residential structures.
               opportunities for coastal recreation, leading to        Building infrastructures that would serve ocean-
               pressure to develop resort areas and single-family      hazard areas--such as roads, bridges, water and
               homes along the beach. The consequences of this         sewer lines, and erosion-control structures-is
               development are increased exposure to storms            allowed only if the structures will be reasonably
               and the potential for loss of life and property, as     safe from coastal hazards and will not promote
               was vividly demonstrated in South Carolina when         additional development in hazardous areas. The
               Hurricane Hugo hit two years ago.                       state also provides hazard notices to all permit
                  Another problem, although less dramatic     ' is     applicants. The notices give the erosion rate in the
               the interference of development with natural            area, note that bulkheads and seawalls are not al-
               shoreline processes. Erosion control structures,        lowed, and wain that the area is hazardous and
               such as seawalls and bulkheads, have the ironic         the property owner is at risk.
               effect of accelerating erosion, either in front of         (2) South Carolina's 1988 Beachfront Man-
               the development the structure is designed to pro-       agement Act provides a comprehensive approach
               tect, or downdrift. In addition, these structures       for managing the state's beach and dune system.
               inhibit the ability of the beach to absorb storm        The act requires the South Carolina Coastal
               energy, thus exposing structures to the full force      Council  to determine local erosion rates for all
               of wind and waves.                                      portions of the coast, except areas already pro-
                  However, decision makers in the private and          tected from development, and to establish devel-
               public sectors should avoid basing policies on          opment setbacks derived from expected beach
               preconceptions regarding typical shorelines and         erosion over 40 years. To help preserve the beach
               their state of development. Establishing setbacks       and ensure that the act's 40-year retreat goal was
               for new development, relocating endangered              realized, the act prohibits all new erosion-control
               structures, providing beach nourishment, building       structures and requires that such structures dam-
               protective structures, or doing nothing may each        aged more than 50% be removed. The act also
               be appropriate under specific local conditions.         requires the disclosure of specific hazardous con-
                                                                       ditions during property transfers.
               State Responses Around the U.S.                            In September 1989, Hurricane Hugo provided
                  Currently, 13 states have some form of setback       a severe test of the Beachfront Management Act.
               requirement for coastal development. Many states        Since the hurricane struck, the state has faced po-
               also have laws to protect dunes, which are the          lifical and legal pressures regarding the implica-
               first line of defense from storms (Maine 1987).         tions of the act for reconstruction and repair of
                                                                       structures along the state's coast. After intense



                                                                                                                         121







                              debate over the future of beach management in             taken a leadership role in planning for the effects
                              South Carolina, the act was amended in June               of possible future rises in sea level. In 1989 the
                              1990. The most significant changes are (1)                commission developed new policies to require
                              strengthened prohibitions against erosion control         that new shoreline development take sea level
                              structures by forbidding the construction of all          rise into consideration. These policies generally
                              erosion control devices, not just vertical struc-         require that any new project requiring fill should
                              tures, and (2) authority for the council to issue a       be above the highest estimated tide level for the
                              special permit when its restriction on develop-           design life of the development. The commission
                              ment would render a lot unbuildable (owners are           also has been working with Bay Area local gov-
                              required to remove the structure if it becomes            eniments to assist them in addressing future sea
                              situated on the active beach through erosion pro-         level rise.
                              cesses). Enforcement of the act has received                  (7) The Delaware Coastal Management Pro-
                              strong support from the South Carolina Supreme            gram has prepared a report which assesses man-
                              Court, as I will discuss later.                           agement alternatives to address shoreline erosion
                                 (3) The Rhode Island Coastal Resources Man-            along Delaware's Atlantic coast over the next
                              agement Council has mapped critical erosion ar-           decade. The report concluded that a policy of re-
                              eas and calculated average annual erosion rates           treat from the coast was the only viable long-
                              for those areas. 'Me state uses the information to        term option, but also proposed a short-term
                              establish building setback lines in areas of in-          action plan, since implemented, to renourish
                              tense erosion. Additionally, the council has              beaches where economically justified.
                              adopted a poststorm policy which authorizes a                 (8) In June 1989 the Hawaii Coastal Zone
                              moratoriurn of up to 30 days on reconstruction of         Management Program completed the "Hawaii
                              structures in specific zones at least 50% de-             Shoreline Erosion Management Study," which
                              stroyed by storm, flood, wave, and wind damage.           provided a comprehensive review of erosion
                              During the moratorium, the state may consider             management in Hawaii. This was a critical step
                              purchasing damaged properties or pursue other             toward developing consistent regulations govem-
                              mitigation responses.                                     ing the use of structural and nonstructural mea-
                                 (4) In July 1989 the Michigan State Legisla-           sures to control erosion. The study recommended
                              ture amended the state's Sand Dunes Protection            that the Hawaii coastal prograrn take the lead in
                              and Management Act to grant the state Depart-             working with county goverriments to develop
                              ment of Natural Resources authority to regulate           local long-term plans for managing erosion in
                              activities within newly defined "Critical Dune            erosion-prone areas.
                              Areas." Key provisions of the act include the des-            (9) In the Australian states of Victoria and
                              ignation of 70,000 acres of Critical Dune Areas,          Tasmania, local governments have factored into
                              the establishment of a model zoning plan for the          their coastal development decisions the possibil-
                              protection of sand dunes, and an option for local         ity of sea level rise. Up and down Australia's ex-
                              governments to administer the act. The amend-             tensive coastlines, structural responses to coastal
                              ments prohibit certain uses in Critical Dune Ar-          erosion are being reduced in favor of
                              eas unless the administering authority grants a           renourishment of heavily used beaches, com-
                              variance.                                                 bined with dune restoration and protection pro-
                                 (5) Using the results of a recent study, the           grains. Officials am stringently reviewing coastal
                              Massachusetts Coastal Zone Management Pro-                sand-mining practices and policies. The Austra-
                              grain has developed policies that require a review        lian federal and Queensland state governments
                              of projects proposed in the 100-year floodplain to        plan to jointly nominate Fraser Island, the
                              determine the effects of relative sea level rise as       world's largest sand island, to the World Heri-
                              well as the project's potential to exacerbate those       tage conservation list in order to preserve it for
                              effects.                                                  future generations.
                                 (6) In California the San Francisco Bay Con-
                              servation and Development Commission has


                              122






                 Federal Responses in the U.S.                              property by eliminating development and rede-
                                                                            velopment in high-hazard areas ... and anticipat-
                    In Washington, D.C., Congress continues to              ing and managing the affects of potential sea
                 wrestle with the legal and policy aspects of               level rise." As Oregon's coastal zone manage-
                 coastal hazards management. For example, the               ment agency, DLCD could seek 309 funds for
                 proposed National Flood Insurance, Mitigation,             what I believe would be a very timely review of
                 and Erosion Management Act of 1991 would                   the legal and policy framework for coastal natural
                 phase out federal flood insurance coverage for             hazards management in Oregon. Those compo-
                 existing development and prohibit such insurance           nents include goals 7, 17, and 18 of the statewide
                 for new development in designated erosion-prone            land-use planning program; the Removal-Fill law
                 coastal areas.                                             (ORS 196.800,990), administered by the Divi-
                    Under the Coastal Barrier Improvement Act of            sion of State Lands; and the Shoreline Construc-
                 1990, the United States Fish and Wildlife Service          tion law (ORS 390.605-.770), administered by
                 is required to map all areas along the Pacific             the Parks and Recreation Division of the Depart-
                 coast, except Alaska, that might qualify for addi-         ment of Transportation.
                 tion to the federal Coastal B anier Resources Sys-           As my summary of recent state and federal
                 tem established on the Atlantic and Gulf coasts            legislative developments indicates, Oregon would
                 under legislation enacted in 1982. That legislation        not be alone in taking a hard look at its coastal
                 prohibits any form of federal assistance, including        hazards laws and policies during the 1990s.
                 federal flood insurance in coastal areas desig-
                 nated as part of the coastal barrier system. Under
                 the 1990 amendments, the Interior Department               Judicial Support for State and Local
                 will recommend to Congress those Pacific coast             Hazards Management
                 areas that state governors deem are appropriate              Certainly many of the state coastal hazard pro-
                 for inclusion in the federal coastal barrier system.       grains I have just described have resulted in in-
                 Eldon Hout and Paul K     larin of the Oregon De-          creased restrictions on coastal development. The
                 partment of Land Conservation and Development              validity of some of those restfictions has been
                 (DLCD) are working closely with the Fish and               challenged in the state and federal courts. In pre-
                 Wildlife Service in an attempt to avoid the many           paring this paper I have done an extensive survey
                 mapping errors that occurred in the Interior               of relevant state and federal court decisions and
                 Department's earlier effort to map Oregon coastal          can report to you that almost uniformly the courts
                 barriers.                                                  have supported the enforcement of development
                    Building on the federal model, Maine's coastal          restrictions based on credible scientific evidence
                 program has developed a state Coastal Barriers             of a hazard to life or property (Mack 1983; Town
                 Resource System. State expenditures for develop-           199 1). In the extreme situation where property is
                 ment activities within the Maine coastal barrier           rendered undevelopable by serious hazards, they
                 system are prohibited. Depending on the Outcome            have supported the enforcement of such restric-
                 of the federal process regarding Oregon coastal            tions without requiring compensation to the af-
                 barriers, Oregon might want to establish a state           fected landowner.
                 coastal barrier system like Maine's.                         Indicative of this trend of strong judicial sup-
                    Section 309 of the federal Coastal Zone Man-            port is a series of decisions rendered by the South
                 agement Act Amendments of 1990 established a               Carolina Supreme Court (Beard 199 1; Lucas
                 new federal grant program to encourage coastal             1991) upholding the restrictions of South
                 states like Oregon to improve their federally ap-          Carolina's Beachfront Management Act on re-
                 proved coastal zone management programs in                 construction of properties damaged by Hurricane
                 several areas, including the management of                 Hugo (Beatley 1990). The South Carolina Su-
                 coastal natural hazards. The clear thrust of section       preme Court is probably as supportive of private
                 309 is toward further "preventing or significantly         property rights as any state court in the nation.
                 reducing threats to life and destruction of                Yet the court has upheld stringent enforcement of


                                                                                                                                    123







                            the South Carolina act's restrictions on recon-          governmental entity has regulated property un-
                            struction in hazardous locations without compen-         constitutionally. Regulations based on inadequate
                            sation to the affected landowners, finding that the      evidence or on poorly documented evidence of
                            well-documented public harms that flow from              course remain vulnerable to judicial invalidation
                            development in hazardous locations justify such          (Annicelli 1983; Saint Joe Paper 1988).
                            regulation (Carter 1984). A federal court of ap-            At this time it seems appropriate to assess the
                            peals just below the U.S. Supreme Court also has         current state of knowledge regarding natural
                            upheld the validity of the South Carolina act            hazards on the Oregon coast and the risks they
                            (Esposito 1991).                                         pose to life and property, both public and private.
                               These decisions regarding the South Carolina          Flowing from that assessment could be an
                            act join recent court decisions regarding similar        evaluation of the adequacy of current Oregon
                            legislation in Florida and elsewhere which also          regulatory and planning processes to reduce or
                            have found that regulations strictly controlling         avoid those risks.
                            development in hazardous coastal areas may be               Relevant Oregon court decisions seem to fall
                            enforced without compensation (Arrington 1989;           in line with the general trend I have previously
                            McNulty 1989; Rolleston 1980; Town 1981).                outlined. The Oregon courts have supported pro-
                               The lesson to be derived from these opinions          tection of public access to the state's sandy
                            seems to be that where the legislature makes spe-        beaches through stringent state regulation of con-
                            cific findings regarding the risks posed by coastal      struction on private property seaward of the
                            natural hazards and sets forth policies to, reduce       coastal vegetation line (State Highway Commis-
                            or avoid those risks, the courts generally will sup-     sion 1971). A recent request to build a seawall on
                            port enforcement of those policies (Comment              the beach at Cannon Beach was rejected by state
                            1991; Hwang 1991; Kusler 1989; Pendergrast               and local agencies; the rejections were then up-
                            1984; Pfundstein and Charles 1991).                      held at the trial court level. These actions fall in
                               The trend in the coastal hazards decisions just       line with the general pattern in Oregon courts.
                            described is further supported by a recent Califor-      Any appellate court decision resulting from that
                            Wa decision regarding inland flood hazards (First        particular matter would obviously be an impor-
                            English 1989). That decision upheld a Los Ange-          tant indicator of future directions in the Oregon
                            les County moratorium on redevelopment in a              courts with respect to the control of shoreline
                            flood-prone creek pending study of the safety is-        construction for reasons of natural hazards as well
                            sues involved against a challenge that property          as public access.
                            affected by the moratorium was being unconstitu-
                            tionally taken without compensation. This case           Accommodating Public and Private
                            had been sent back to the California court by the        Interests in Coastal Hazards Manage-
                            U. S. Supreme Court after it rendered its famous         ment
                            decision in the First English Evangelical case,
                            which ruled that if local governments did wgulate           As I have said, the courts generally support
                            private property unconstitutionally, they could          enforcement of coastal hazards regulations with-
                            not merely repeal the offending regulation but           out compensation to affected landowners. How-
                            also must pay compensation for any damages suf-          ever, that does not mean that some form of
                            fered by the regulated property owner due to the         compensation may not be provided even though
                            regulation.                                              it is not constitutionally required. Throughout the
                               That basic principle continues to apply to            nation and in Oregon we need to give more
                            coastal hazards regulation as well. However, the         thought to schemes that recognize the sometimes
                            resulting California court decision and the coastal      dramatic impacts of nature on coastal property
                            hazards decisions seem to stand for a very impor-        owners and that attempt to accommodate affected
                            tant point: that when a coastal hazards regulation       private interests wherever possible. Techniques
                            is based on credible scientific evidence, the courts     for achieving such accommodation include (1)
                            are very unlikely to hold that the regulating            acquiring outright fee simple or less than fee


                            124







                 simple interests such as conservation easements               (1) Are structural protection devices always
                 in affected coastal properties, (2) reducing prop-         bad for the adjacent beach and neighboring prop-
                 erty tax values and rates, and (3) awarding den-           erties, or is that an overgeneralization?
                 sity bonuses and transferrable development rights             (2) Should alteration of dunes for view preser-
                 to affected property owners.                               vation and similar purposes continue to be autho-
                    I understand that in coastal Oregon some local          rized by goal 18?
                 governments have provided for density bonuses                 (3) Are the true and total costs, both direct and
                 to be awarded to developers who avoid hazardous            indirect, of coastal development and coastal pro-
                 areas. Their experiences need to be documented.            tection works currently being fairly allocated?
                 Ideally such accommodations should be worked                  Oregon's current approaches to coastal haz-
                 out at the local level.                                    ards need revision regardless of whether the Or-
                    In that connection, I recently heard a                  egon coast will or will not be significantly
                 consultant's presentation on the development of a          affected by any sea level rise caused by global
                 local wetlands conservation plan for Rockaway              warming. And if at some point in the future, offi-
                 Beach. The process was moving forward with                 cials and scientists reach the consensus that accel-
                 extensive local participation. The consultant ac-          erated sea level rise poses risks to Oregon, the
                 knowledged that there clearly would be some                state's revised coastal hazards program will cer-
                 winners and losers locally in the designation of           tainly be the starting point for designing and
                 wetlands on privately owned property and in the            implementing adaptive responses (Corfield 1987;
                 community decision making about their future.              Rychlak 1990; Titus 1991, 1990).
                 Wetlands conservation has reached the highest                 In conclusion, and in a more philosophical
                 political levels in this nation, and local wetland         vain, I believe three emerging international prin-
                 owners are faced with a great deal of uncertainty          ciples governing resources development (morally
                 and a period of rapid change in federal and state          but not legally binding at this point) are relevant
                 laws, policies, and court decisions. However,              to revisions in Oregon hazards law and policy:
                 what impressed me was that it appeared there                  (1) the "polluter pays" principle-the notion
                 would at least be some local winners in the                that any development allowed in hazardous
                 Rockaway Beach process. Without such a local               coastal areas should pay its full costs;
                 effort, wetland owners in Rockaway Beach might                (2) the precautionary principle-the notion
                 only be losers in trying to deal with the rapidly          that in the absence of good information about a
                 changing complexities of federal and state wet-            coastal development's safety and impacts on ad-
                 land law and policy.                                       jacent beaches and neighboring properties, we
                                                                            don't move forward with it until we have better
                                                                            information; and
                 Implications for Oregon Coastal Haz-                          (3) the principle favoring sustainable develop-
                 ards Management                                            ment of resources over unsustainable develop-
                    We know a lot more about coastal processes              ment-building in hazardous coastal locations
                 and coastal engineering and their effects and limi-        generally is not a sustainable use of those re-
                 tations than we did when Oregon put in place its           sources.
                 current scheme for coastal natural hazards man-
                 agement. The time may be right to review that
                 scheme and, where appropriate, revise it through           References
                 legislative action, administrative rule making,            Annicelli v. Town of South Kingstown, 463 A.2d
                 comprehensive plan revisions, and related pro-                133 (R.I. Sup. Ct. 1983).
                 cesses. Furthermore, some federal dollars may be           Arrington v. Mattox, 767 S.W.2d 957 (Tex. Ct.
                 available to assist in that effort.                           App. 1989).
                    Following are some questions that need to be            Beard v. S.C. Coastal Council, 403 S.E.2d 620
                 reexamined:                                                   (S.C. Sup. Ct. 1991).



                                                                                                                                    125







                           Beatley, Managing Reconstruction Along the          NOAA OCRM, Coastal Management Solutions
                           I South Carolina Coast (U. of Colorado 1990).           to Natural Hazards (Technical Assistance
                           Carter v. S.C. Coastal Council, 404 S.E.2d 895          Bulletin #103, 1990).
                              (S.C. Sup. Ct. 1984).                            Pendergrast, The Georgia Shore Assistance Act,
                           Coastal Barrier Improvement Act of 1990.                17 Natural Resources Law 397 (1984).
                           Coastal Zone Management Act Amendments of           Proposed National Flood Insurance, Mitigation,
                              1990, section 309 (16 U.S.C. ï¿½ 1456b).               and Erosion Management Act of 1991 (H.R.
                           Comment, Shifting Sands and Shifting Doctrines,         1236, S. 1650).
                              79 California Law Review 205 (199 1).            Pfundstein & Charles, Florida's Coastal Con-
                           Corfield, Sand Rights: Using California's Public        struction Regulations and the Taking Issue:
                              Trust Doctrine to Protect Against Coastal            The Complexities of Drawing Lines in the
                              Erosion, 24 San Diego L. Rev. 727 (1987).            Sand, 6 J. Land Use & Envtl. Law 255 (1991).
                                                                               Rolleston v. State, 266 S.E.2d 189 (Ga. Sup. Ct.
                           Esposito v. S.C. Coastal Council, 60 U.S. Law
                              Week 2065 (4th Cir. 199 1).                          .1980).
                           First English Evangelical v. County of Los          Rychlak, Thermal Expansion, Melting Glaciers,
                                                                                   Rising Tides: The Public Trust in Mississippi,
                              Angeles, 210 Cal. App. 3d 1353,258 Cal.
                              Rptr. 893 (1989).                                    .11 Mississippi College Law Review 1 (1990).
                                                                               Saint Joe Paper v. Department of Natural Re-
                           Hwang, Shoreline Setback Regulations and the            sources, 536 So. 2d 1119 (Fla. Ct. App. 1988).
                              Takings Analysis, 13 Hawaii L. Rev. 1 (1991).    State Highway Commission v. Fultz, 261 Or.
                           Kusler, Avoiding Public Liability in Floodplain         289,491 P.2d 1171 (1971).
                              Management (Association of State Floodplain      Titus, Greenhouse Effect and Coastal Wedand
                              Managers 1989).                                      Policy, 15 Envtl. Mgmt. No. I at 39 (1991).
                           Lucas v. S.C. Coastal Council, 404 S.E.2d 895
                              (S.C. Sup. Ct. 1991).                            Titus, Strategies for Adapting to the Greenhouse
                           Mack v. Town of Cape Elizabeth, 463 A.2d 717            Effect, APA Journal Summer 1990 at 311.
                              (Me. Sup. Ct. 1983).                             Town of Indialantic v. McNulty, 400 So.2d 1227
                           Maine Department of Environmental Protection            (Fla. Ct. App. 1981).
                              Dune Rule 355 (1987).                            Town of Palm Beach v. Department of Natural
                                                                                   Resources, 577 So. 2d 1383 (Fla. Ct. App.
                           McNulty v. Town of Indialantic, 727 F. Supp.            1991).
                              604 (M.D. Fla. 1989).

























                           126






                  CALIFORNIA'S COASTAL HAZARDS                                                                                              PUBLIC POLICY-
                  POLICIES: A CRITIQUE                                                                                                       0
                  Gary B. Griggs                                                                                                                          L2ot
                                                                                                                                             Z
                  Department of Earth Sciences, University of California, Santa Cruz
                  James E. Pepper                                                                                                                        3
                  Department of Environmental Studies, University of California, Santa Cruz                                                 COASTAL
                  Martha E. Jordan                                                                                                          HAZARDS POLICY
                  Santa Cruz County Planning Department                                                                                     ISSUES ON THE
                                                                                                                                            WEST COAST



                  Introduction                                                   erosion, and tidal waves (tsunami waves).
                  In adopting the 1972 California Coastal Initiative,            The Plan proposes policies to restrict new
                  the public set a new statewide direction in coastal            development in floodplains, require that a
                  land use. Seeking to reverse the incremental,                  geologic hazards description be made a part
                  piecemeal, sprawling pattern of development that               of residential sales information, place
                                                                                 limitations on uses of land within coastal
                  had already overrun many coastal areas and de-                 areas of highest risk, prevent public subsi-
                  graded the quality of the contiguous public trust              dies for hazardous development, and provide
                  lands, the people were unequivocal regarding the               setbacks from erosion-prone bluffs. (Coastal
                  primacy of coastal protection, declaring: "Me                  Commission 1975)
                  permanent protection of the remaining natural
                  and scenic resources of the coastal zone is a para-            A related recommendation concerned safe-
                  mount concern to present and future residents of            guarding against the harmful effects of seawalls,
                  the State and nation" (State of California 1972).           breakwaters, and other shoreline structures:
                     The California Coastal Zone Conservation                    Seawalls, breakwaters, groins, and other
                  Commission (hereinafter referred to as the                     structures near the shoreline can detract from
                  Coastal Commission) was created through this                   the scenic appearance of the oceanfront and
                  citizen initiative and was charged with the prepa-             can affect the supply of beach sand. The plan
                  ration of a Coastal Plan for subsequent legislative            limits the construction of shoreline structures
                  approval. This plan, completed in 1975, was de-                to those necessary to protect existing build-
                  signed to achieve two objectives: "(1) protect the             ings and public facilities, and for beach
                  California coast as a great natural resource for the           protection and restoration. Special design
                  benefit of present and fliture generations; and (2)            consideration is proposed to insure continued
                  use the coast to meet human needs in a matmer                  sand supply to beaches, to provide for public
                  that protects the irreplaceable resources of coastal           access, and to minimize the visual impact of
                  lands and waters" (Coastal Commission 1975).                   structures. (Coastal Commission 1975)
                  Among the major findings and recommendations
                  was a policy statement formulated to provide pro-              This paper reports on the results of these and
                  tection against natural hazards:                            other coastal hazard policy recommendations for-
                     Development along the coast of California is             warded to the State Legislature by the Coastal
                     threatened by a number of natural hazards                Commission. Three major problem areas are ad-
                                                                              dressed: (1) limitations on hazard identification
                     such as floods, earthquakes, landslides, cliff           and evaluation; (2) hazard liability issues; and (3)
                                                                              variation and effectiveness in policies and prac-
                                                                              tices goverriing (a) blufftop and beach-level de-
                  *Reprinted, with permission of the publisher, ftom          velo ment, (b) emergency conditions and
                  The California Coasial Zone Experience, 199 1, T.H.              p
                  Wakeman and G.W. Domurat, eds., Long Beach, CA:             reconstruction, and (c) emplacement of coastal
                  American Society of Civil Engineers, pp. 89-107.            protection structures.


                                                                                                                                    127






                             Background                                              less expensive (Griggs 1986), although it is likely
                                                                                     that this option is not often seriously considered
                             Human Adaptations and Responses to Coastal              by most threatened oceanfront property owners
                             Hazards                                                 simply because of a desire to protect their ocean
                                The range of human responses and adaptations         view at any cost.
                             to natural hazards varies widely. Burton identi-           Historically, the third and most common ap-
                             fied major modes of coping with natural hazards:        proach to protecting private or public structures
                             (1) loss absorption, (2) hazard acceptance, (3)         or utilities from coastal hazards has been the con-
                             hazard reduction, and (4) change in use and live-       struction of some type of "hard" protective struc-
                             lihood in hazard areas (Burton et a] 1978). These       ture. Protective devices can vary considerably in
                             modes generally occur sequentially over time,           type, size, effectiveness, and life span (Fulton-
                             reflecting movement across discernible threshold        Bennett and Griggs 1986). The purpose of any
                             levels-hazard awareness, action, and                    hard structure, regardless of type, is essentially
                             intolerance.                                            the same: reduce or halt the adverse impacts of
                                'Me extent to wl-dch a society or commui*y           wave attack and shoreline erosion and thereby
                             remains unaffected by natural processes is its ab-      protect threatened structures and property.
                             sorptive capacity. When adverse changes are rec-           A fourth option, beach nourishment or replen-
                             ognized as losses, but remain tolerated, a pattern      ishment, has emerged as an appealing "sofr'ap-
                             -of loss acceptance develops as the inhabitants         proach to dealing with the problems of shoreline
                             learn to accept the costs of living in a hazard         erosion in sandy beach environments. On the sur-
                             prone environment. When people reach the limits         face this strategy presents an attractive compro-
                             of loss acceptance, they attempt to control the         mise to the extremes of abandoning the shoreline
                             force of the natural hazard, and thus reduce their      or armoring it with concrete or rock. The beach is
                             vulnerability to the loss of property and life. If      nourished or replenished with sand, from either
                             loss reduction ultimately proves to be ineffective      an offshore or inland source, to increase the
                             or too costly, substantial changes in the types of      width of the beach such that it serves as a more
                             land uses or the relocation of uses from hazard-        effective buffer and protects the shoreline from
                             ous areas becomes an important alternative in the       wave attack, thereby reducing erosion. However,
                             choice of response and adaptation.                      the economics of a large-scale beach nourish-
                                The lowest cost and potentially highest risk         ment program and the distribution of costs pose
                             approach to coastal hazard mitigation is to do          serious questions for this approach to coastal
                             nothing. Depending upon the particular loca-            protection.
                             tion-its setback from the sea, elevation of the            In terms of minimizing economic costs and
                             structure, past erosion or inundation problems-         environmental impacts, a fifth option--coastal
                             this approach may work for a limited period of          hazard avoidance, ranks highest Not only are the
                             time. 'Mere is no cost until a major storm finally      public costs associated with disaster relief, con-
                             does occur, and then either a rapid emergency           struction of protective devices, and government
                             response is necessary or losses may be very high.       assistance insurance reduced or eliminated, so
                                Relocation of oceanfront structures or utilities     too are the adverse environmental effects of
                             is a second option. Where a parcel is large             coastal protection structures on contiguous public
                             enough, a threatened structure can be moved             trust lands. The principal limitation of the hazard
                             landward on the same parcel to extend the period        avoidance strategy is the political cost associated
                             of protection, depending upon average erosion           with the denial of private development in high
                             rates. In many cases this will not be possible and      risk areas. The mechanisms available for a haz-
                             relocation will require acquisition of a separate       ard-avoidance strategy are land use planning and
                             lot. Recent examples of comparative costs of re-        regulation or public purchase of property rights
                             location or reconstruction versus protection have       in high risk areas through easements, life estates,
                             indicated that in the long run, relocation is far       or fee-simple ownership.



                             128






                 California Population Growth and Concentra-               A comprehensive coastal hazards policy must
                 tion                                                      necessarily recognize both geologic and demo-
                    Coastal hazards are a function of the presence         graphic variables within the coastal zone.
                 of human beings and their myriad activities in            California's Coastal Hazards: Types and Dis-
                 interaction with naturally occurring coastal pro-         tribution
                 cesses. With the exception of changes due to                 The physical environment of the west coast of
                 coastal erosion, the coastline has the same general       the United States is strikingly different from that
                 configuration as it did in 1850 when the estimated        of either the east or Gulf coasts. Even a casual
                 population of California was 93,000 persons. The          visitor to the California shoreline will notice the
                 state population grew steadily for the next 100           obvious differences between the coastal moun-
                 years, but following World War II, it virtually           tains and seacliffs characteristic of California's
                 exploded: between 1950 and 1970 it nearly                 western margin and the broad, flat coastal plains,
                 doubled, growing from 10.6 to 20 million. The             sand dunes, and barrier islands of New Jersey or
                 1990 population of 29.8 million represents a 16-
                 fold increase since 1900 and a near tripling since        North Carolina. The east and west coasts of North
                 1950. Of all the coastal states, only Florida has         America have very different geologic histories
                                                                           and, as a result, have very different landforms and
                 experienced a slightly more dramatic percent in-          pose substantially different problems for
                 crease in population (I 8-fold since 1900),;al-           human use.
                 though the absolute numbers of people is only a              Tectonic plate interactions along the length of
                 third of the California population.                       the state have produced such diverse features as
                    An estimated eighty percent of the state's             the San Andreas Fault and its associated earth-
                 population lives within 30 miles of the shoreline         quakes, the rugged coastal mountains of Big Sur
                 (Griggs and Savoy 1985). Estimates compiled               and Mendocino, and the uplifted marine terraces
                 through our research indicate that approximately          and coastal cliffs which characterize much of the
                 3.6 million people five within three miles of the         coastline. The entire state, particularly the shore-
                 coast. Land use pressure on the California coast-         line, is geologically active; landforms are con-
                 line resulting from population growth over the            stantly changing and evolving, although at
                 past 50 years is arguably twice as great as for any       different scales and rates. Some of these pro-
                 other state. With a coastline of 1, 100 miles and a       cesses operate continuously (waves breaking on
                 population of nearly 30 million persons, there are        the shoreline, for example), others occur season-
                 over 27,000 residents for each mile of coastline.         ally (flooding due to prolonged or high intensity
                    This population is not equally distributed             rainfall), while still others occur relatively infre-
                 along the entire length of the coast. Rural               quently (large earthquakes).
                 Mendocino County, for example, with 120 miles                A diversity of forces and processes interact on
                 of coastline, has a population of approximately           the coast, making it one of the world's most dy-
                 77,000 or about 640 residents per mile of shore-          namic environments. Waves, fides, winds,
                 line. By contrast, Los Angeles County has a 74_
                 mile coastline and a population of 8.65 million           storms, rain and runoff, as well as human activity,
                 people. Each mile of this county's coastline thus         act to build up, wear down, and continually re-
                 44serves" over 117,000 persons, not including the         shape this continental edge. These forces in turn
                 large tourist population drawn to the area.               interact with a wide spectrum of geologic condi-
                    Because areas with exceptionally high popula-          tions to produce several types of hazard condi-
                 don are likely to have heavier use of coastal re-         tions. In California, coastal geologic hazards
                 sources and higher concentrations of coastal              occur most frequently in the form of shoreline
                                                                           erosion (both seacliff and beach) and coastal
                 development, it is clear that the type, magnitude,        flooding (both wave impact and inundation). Hu-
                 and distribution of coastal hazard risk will vary         man-induced interference with coastal processes
                 not only as a result of different physical condi-         (littoral drift, onshore and offshore sand move-
                 tions and geomorphic processes along the coast-
                                                                           ment, dune and back-beach formation, etc.) can
                 line, but also as a result of demographic variation.      exacerbate hazard conditions.

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                              A 1971 inventory of the Califort-da shoreline       (12 percent) of the state's ocean shoreline con-
                           classified only 14.2 percent as "non-eroding." Of      tains some form of "hard," engineered protective
                           the remaining 85.8 percent, 80.4 miles (4.4 per-       structure, an increase of slightly greater than 50
                           cent) were classified as "critical erosion," with      percent in only four years, and nearly a four-fold
                           the remainder designated as "non-critical ero-         increase in 18 years.
                           sion" (COE 197 1). The following year, a Califor-         When particular areas of the coastline are ex-
                           nia Department of Navigation and Ocean                 amined, the increasing degree of protection re-
                           Development plan reported that only 120 miles of       quired to maintain oceanfront property is
                           the ocean shoreline were naturally protected from      staggering. For example, 74 percent of the nine
                           the open ocean, with an additional 50 miles            miles of northern Monterey Bay now contains
                           semiprotected. The remaining 850 miles were            "hard" protective structures, as does 77 percent of
                           classified as "exposed," nearly 250 miles of           the 18 -mile coastal reach extending from
                           which were in urban or semi-urban uses in 1972         Carpenteria to Ventura. Some 86 percent of the 8
                           (COAP 1972).                                           miles of coastline between Oceanside and
                              No inventory of coastal hazards was set forth       Carlsbad has been armored, and the 8-mile reach
                           in the 1975 California Coastal Plan or in the vati-    between Dana Point and San Clemente is virtu-
                           ous background reports prepared in support of its      ally a continuous system of protective structures
                           development. A subsequent investigation by the         (Griggs and Savoy 1995; Griggs 1987).
                           California Department of Navigation and Ocean
                           Development (Habel and Annstrong 1977) de-             Adverse Effects of Development on
                           fined the erosion problem somewhat differently         Coastal Process
                           than the COE. Approximately 100 miles (10.9
                           percent) of the coastline were delineated as erod-        In recent years there has been a growing real-
                           ing with existing development threatened, and an       ization that many human activities (including
                           additional 300 miles (29.5 percent) were classi-       damming of coastal rivers and construction of
                           fied as eroding at a rate fast enough that future      jetties, breakwaters, and coastal protection struc-
                           development would eventually be threatened.            tures) are adversely affecting beach sand supply
                           Thus a total of 400 miles (39.4 percent) of the        and therefore beach stability and longevity. Since
                           California shoreline were considered to be threat-     the 1950s many southem Califorrda. coastal rivers
                           ened due to high erosion rates. The most recent        have been dammed for water supply and flood
                           inventory of hazardous coastal environments ex-        control. The darns impound water but also trap
                           pands the scale of problem areas. In 1985, 16          sand destined for the coastal beaches and control
                           coastal geologists participated in the preparation     the high-velocity, large discharge flood flows that
                           of a statewide inventory of coastline conditions,      transport the greatest volumes of sand to the
                           classifying 315 miles (28.6 percent) as "high          beaches. Thus the benefits of flood control and
                           risk" and an additional 405 miles (36.8 percent)       increased water supply have been partially offset
                           as "caution" (Griggs and Savoy 1985). These            by the gradual reduction of sand input to the lit-
                           data indicate that two-thirds of the California        toral system and the corresponding reduction in
                           coastline constitutes a significant coastal hazard.    the level of coastal protection provided by
                           The Extent of Coastal Protection Structures            beaches.
                              The 1971 Corps of Engineers inventory of               Where seacliff or bluff erosion is a major
                           coastal conditions indicated that 26.5 miles of        source of beach sand, which is the case along the
                           coastline (approximately 2.5 percent) contained        shoreline of northern San Diego County,
                           some form of "hard" protective structure (COE          armoring the coastline reduces beach sand sup-
                           197 1). In the 14 years between 1971 and 1985, an      ply. Placing coastal protection devices adjacent to
                           additional 58.5 miles were armored (Griggs and         sea cliffs which produce significant volumes of
                           Savoy 1985). Our recent investigation (conduct         beach materials reduces beach sand supply, al-
                           through interviews with local government plan-         though no comprehensive evaluation of this im-
                           iiing staff) indicated that as of 1989, 130 miles      pact on beach sand supply has been conducted for
                                                                                  the state's coastline.


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                   Along the urbanized seacliffs of southern Cali-          Although nearly 20 years have elapsed since the
                 fomia, geologic instability has been increased             California public voted for the creation of the
                 through the addition of large volumes of irriga-           state's Coastal Commission and 14 yews have
                 tion water required to maintain lawns and non-             passed since the legislature passed the California
                 native vegetation in the yards of cliff top homes.         Coastal Act, there remains a wide disparity in
                 Landscape irrigation alone is estimated to add the         governmental responses to coastal hazards. At the
                 equivalent of 50 to 60 inches of additional rainfall       time the Coastal Initiative was approved by the
                 each year to garden and lawn areas. This iriiga-           voters, the principal issues were environmental
                 tion has led to a slow, steady rise in the water           concerns, beach access, and wetlands protection.
                 table that has progressively weakened cliff mate-          Issues of coastal storm damage, shoreline retreat,
                 rial and lubricated joint and fracture surfaces in         littoral drift and sand availability were not as
                 the rock along which slides and block falls are            apparent and pressing as they are today. As a
                 initiated. In addition to these effects, surface run-      result, Coastal Act policy statements and subse-
                 off discharged through culverts at the top or along        quent Interpretive Guidelines are notably defi-
                 the face of the bluffs leads to gullying or failure        cient in these areas.
                 of weakened surficial materials.                             For these reasons, as well as the astronomical
                    Where a seawall or revetment extends a sig-             value of coastal property and a notable lack of
                 nificant distance seaward of the cliff or bluff, the       political will to confront geologic hazard issues,
                 beach landward of the structure is permanently             the translation of the acquired knowledge of
                 lost. On a shoreline undergoing net erosion, the           coastal hazards and risks into policies and prac-
                 beach will eventually disappear as the shoreline           tices appears to be deficient at all levels of gov-
                 migrates landward, and the structure will begin to         emment. The objective of this research was to
                 act as a groin, trapping littoral drift upcoast, and       address this deficiency through a systematic
                 producing erosion downcoast. Thus in the case of           analysis and assessment of the coastline policies,
                 a retreating shoreline, the direct effects of sea-         plans, guidelines, and practices of local govem-
                 walls or revetments will be reduced beach width            ments and state agencies.
                 and loss of natural protection from wave attack;             Planning department staff from 34 of the
                 structures, utilities, or facilities are protected but     state's 42 coastal cities and 14 of the state's 15
                 the beach is lost.                                         coastal counties were interviewed. Only those
                    Since most "hard" protective structures are lo-         jurisdictions whose shorelines were completely
                 cated on or directly adjacent to public trust lands,       urbanized and virtually "built-ouC were not in-
                 the visual effects of such structures on the scenic        cluded. Although this research project was di-
                 quality of such public lands is clearly a matter of        rected primarily at local government agencies and
                 public policy. The 130 miles of these hard protec-         their policies and practices, because of the exten-
                 tive structures along the California coast consti-         sive involvement of several state agencies in the
                 tute an adverse visual impact which degrades the           coastal hazards issue, we also reviewed the poli-
                 scenic value of the affected shoreline, and signifi-       cies and practices of three agencies: the Depart-
                 cantly diminishes the natural beauty of these pub-         ment of Boating and Waterways, the Department
                 lic trust lands. The emplacement of protective             of Parks and Recreation, and the Coastal Zone
                 structures can also serve as a barrier or impedi-          Conservation Commission. State-level staff in-
                 ment to both horizontal and vertical public                volved in the coastal programs of these agencies
                 access.                                                    were also interviewed.

                                                                            Local Government Policies and Practices
                 A Summary Assessment of Coastal                               Policies and practices regulating oceanfront
                 Hazard Policies                                            property and its development vary widely
                    In spite of a growing body of scientific infor-         throughout the state. Some communities have ar-
                 mation on the location and nature of coastal               ticulated policies which encourage community or
                 hazards and their associated risks, oceanfront             state purchase of remaining undeveloped ocean-
                 development continues in hazardous areas.                  front property, as well as rigorous guidelines and

                                                                                                                                    131







                             requirements for any new development or protec-            One of the most effective methods of land use
                             tion plans. Others openly encourage shoreline de-       control in coastal hazard areas is the designation
                             velopment adjacent to areas of documented high          of special zones that permit or exclude specific
                             coastal erosion rates. Local politics and econom-       uses or activities. Twenty-four coastal jurisdic-
                             ics and a fear of litigation over property rights       tions recognize coastal geologic hazards in some
                             appear to be the most important factors control-        official manner. There is no state directive, how-
                             ling these policies and practices, rather than the      ever, which ensures mcogn@ition of these hazards
                             history of shoreline erosion and storm inundation.      and the formation of regulatory zones.
                               Our research focussed on seven specific areas            Another effective regulatory tool is the use of a
                             where existing policies and practices raised im-        geologic hazard ordinance. Although only four
                             portant questions: (1) Coastal Hazard Identifica-       local governments use this method, 38 otherjuris-
                             tion, Evaluation, and Review; (2) Preparation of        dictions have comparable regulations which
                             Site-specific Geotechnical Studies; (3) Legal Is-       cover some aspect of hazard management. For-
                             sues Surrounding Hazard Protection Liability; (4)       mal local government designation of coastal geo-
                             Blufftop Development Policies and Practices; (5)        logic hazard areas and land use regulations
                             Beach-level Development Policies and Practices;         governing such areas varies widely. The absence
                             (6) Emergency Condition and Reconstruction              of state-level policy requiring local governments
                             Policies; and (7) Policies Governing Coastal Pro-       to undertake comprehensive identification, evalu-
                             tection Structures. Principal findings for each area    ation, and land use regulation in hazardous areas
                             are summarized below.                                   is a major mason for this lack of consistency.
                             (1) Coastal Hazard Identification, Evaluation, and      (2) Site-specific Geotechnical Studies
                             Review                                                     Detailed site-specific geotechnical studies are
                               A basic assumption in the formulation of land         a virtual necessity in order to evaluate coastal
                             use regulations in hazardous coastal areas is that      hazards. Our findings indicate significant vaiia-
                             local jurisdictions are able to identify these haz-     tion in the type and technical adequacy of
                             ards and adequately assess risks to proposed de-        geotechnical reports and the expertise of person-
                             velopment. Although several generalized                 nel preparing such reports. The lack of adopted
                             statewide inventories of coastal hazards have           guidelines governing the preparation of reports, a
                             been published (COE 197 1; COAP 1972; Habel             shortage of qualified local government staff to
                             and Armstrong 1977; Griggs and Savoy 1985),             review reports, the absence of any independent
                             additional information is needed on a local or          technical review of public agency reports, and a
                             site-specific level. Only five of the local govern-     lack of baseline information against which to
                             ments interviewed through our research had com-         evaluate the conclusions of reports are the pri-
                             pleted detailed geologic studies focussed on local      mary masons for this recuning problem.
                             coastal hazards. Planning department staff cited        (3) Legal Issues Surrounding Coastal Hazard Li-
                             four primary information gaps: coastal erosion          ability
                             rates, sea level rise and its effects, wave runup,         The costs and risks involved in living directly
                             and littoral drift rates. The lack of standards for     on the shoreline can be very high for everyone:
                             the design of coastal protection structures was         property owners, local governments, insurance
                             also a frequently cited information gap. There is
                             no agency or organization formally charged with         companies and lending institutions, as well as
                             the responsibility for developing this important        state and federal disaster relief agencies. The risks
                             information. The Coastal Commission employs             and potential costs of owning property in a haz-
                             only two staff geologists. Although these staff are     ardous coastal environment should be fully dis-
                             occasionally able to undertake research, nearly all     closed to any potential buyer. The 1975 Coastal
                             of their time is spent on pen-nit and site review for   Plan recognized this need in recommending the
                             proposed projects, rather than on developing sci-       following policy, although the subsequent
                             entific information in support of advance               Coastal Act did not include such a provision.
                             planning.


                             132







                     Geologic hazards information developed by             currently represents a significant problem. New
                     qualified personnel and approved by an                developments are still being proposed on eroding
                     appropriate governmental agency for                   or unstable blufftops and older weekend cottages
                     specific areas or sites shall be permanently          are being torn down and replaced by larger homes.
                     filed in the public records of the coastal               Because shoreline erosion was not a priority
                     counties. The full reports shall be cited and         issue at the time the Coastal Act was imple-
                     a summary of all relevant conclusions,                mented, state directives on this particular hazard
                     understandable to the layman, shall be                are somewhat vague. Although the Coastal Com-
                     included as part of the chain of title to             mission issued Statewide Interpretive Guidelines
                     property (and be a nomial part of a title             for determining the geologic stability of blufftop
                     report) and also as part of the state Real            development, there is no state policy establishing
                     Estate Commissioner's report for subdivi-             safe setbacks from the edge of a seacliff or bluff
                     sions. (Coastal Commission 1975)                      for any type of development. Some local jurisdic-
                    In order to bring existing oceanfront develop-         tions use a predetermined, fixed setback although
                 ment within safety-based guidelines, it is critical       these vary from 10 to 320 feet. Others employ a
                 to ensure that all parties involved in the transfer       cliff retreat rate (supposedly site specific) and ap-
                 of title to property exposed to coastal hazards be        plicable over a specific time period, most com-
                                                                           monly a 50-year period.
                 aware of the inherent risks. Only four local Juns-           The Coastal Act is even more lenient in regu-
                 dictions presently require such a disclosure.             lating "infill" development; thus it is not surpris-
                    The flu-eat of lawsuits from coastal property          ing to find wide variation in local government
                 owners has often compromised the regulatory               interpretations of what constitutes "infill." Many
                 process. This can occur either when buildmig per-         . .
                 mits are not granted for proposed new construc-           jurisdictions compromise safe setback consider-
                 tion exposed to geologic hazards or when                  ations in "infill" areas (however defined) due to
                 conditions are imposed on reconstruction permits          intense pressure from coastal property owners
                 following coastal storm damage. Local govem-              and the real estate community, by assuming that
                 ments and private sector geologic consultants am          the setback of adjacent existing development is
                 also concerned over the issue of legal liability in       adequate for future construction as well. As bluff
                 the conduct of their work. The threat of lawsuits         retreat continues, this "stringline" approach to
                 over alleged excessive restrictions on private            d.etermining setbacks is no longer appropriate; it
                 property rights on the one hand, and the consis-          simply extends the hazard exposure to ever more
                                                                           structures.
                 tent and diligent implementation of regulations
                 goveming coastal hazard conditions on the other,          (5) Beach-level Development Policies
                 place these professionals and local government               Damage to beach level residential and com-
                 officials in a very difficult situation, particularly     mercial development was widespread along the
                 given the very high costs of malpractice insur-           California coast in 1978, 1983, and again in 198 8.
                 ance, the high costs of litigation, and the serious       The low-lying communities of Stinson Beach,
                 financial constraints on local governments. In re-        Rio del Mar, Malibu, Oceanside, and Imperial
                 sponse to the threat of litigation, 18 jurisdictions      Beach have been repeatedly damaged by both
                 utilize some form of liability release for projects       wave impact and inundation. Despite California's
                 proposed in hazardous areas.                              intense beach level development, neither the
                 (4) Blufftop Develop   ment Policies                      Coastal Act nor the Interpretive Guidelines
                                                                           specifically recognized the hazards of direct wave
                    Coastal communities from San Diego to Eu-              impact or wave/tidal inundation (coastal flood-
                 reka have lost entire ocean-front streets and lots        ing) on beach level structures. Most of the state's
                 through the ongoing process of bluff retreat over         coastal jurisdictions have adopted FEMA Flood
                 the past century. Moss Beach, Capitola, Isla              Insurance Rate Maps which delineate zones that
                 Vista, Palos Verdes, Encinitas, and Solano Beach          are subject to different degrees of coastal
                 are examples of areas where bluff retreat


                                                                                                                                  133







                               flooding. Although these maps Were originally               construction of a protective structure be part of
                               developed for insurance purposes, they now have             the normal development process.
                               regulatory status. The lack of state guidelines for             Because of high construction costs ($750 to
                               safe development at beach-level has led to                  $3000/linear foot or $4 million to $16 million/
                               continued development and reconstruction in                 mile) and high maintenance and repair costs,
                               hazardous locations.                                        shoreline protection is a major investment, often
                               (6) Emergency Condition and Reconstruction                  subsidized by state or federal programs or insur-
                               Policies                                                    ance monies. The existing level of coastal protec-
                                  The Coastal Act contains provisions permit-              tion in California represents an investment of
                               ting immediate actions to be taken without ob-              between $500 million and $2 billion (1990 dol-
                               tairiing a regular Coastal Development Pen-nit              lars) in an attempt to halt erosion along 130 miles
                               when public or private properties are threatened            of shoreline. Private property owners and public
                               in emergency situations. However, the experience            agencies alle must r1balize that armoring the
                               of coastal jurisdictions with the Emergency Per-            shoreline is a very expensive, and often only tem-
                               mit process indicates that a serious policy gap ex-         porary, solution to the problem. It is time to take a
                               ists: there is no link between emergency response           critical look at the costs and benefits of additional
                               procedures established to protect and maintain              shoreline protection. At least two states, North
                               threatened development and the long-term repair             Carolina and Maine, have recently enacted legis-
                               and reconstruction on such sites. Nearly all mate-          lation which prohibits the construction of "hard"
                               rials emplaced under emergency conditions pro-              protective structures. Relocation of buildings to
                               vide only short-term protection. Provisions                 safer sites or replenishing the beach's sand supply
                               goveniing the removal of emergency protection               are the favored alternatives in those particular
                               structures and the review of the stability or safety        states.
                               of a thmatened or damaged principal structure are               Although relocation of a structure may be less
                               often ambiguous and have led to considerable                costly than armoring the shoreline, this approach
                               litigation.                                                 is rarely a seriously considered option since most
                                  Coastal Act policies also facilitate the rebuild-        shoreline residents are unwilling to forego the
                               ing of damaged and destroyed structures in essen-           loss of an oceanfront view. However, relocation,
                               tially the same form and location as the original           dismantling, or abandonment of oceanfront
                               structure by eliminating the need for a Coastal             homes will soon be the only possible alternative
                               Development Permit. As a result, rebuilding does            at some sites due to difficult geologic conditions,
                               not undergo the same scrutiny as new projects,              as well as land ownership and access consi-
                               and reconstruction in proven high risk situations           derations.
                               is commonplace.                                                 A number of southern California's coastal
                                                                                           commuriities are now evaluating beach nourish-
                               (7) Policies Goveniing Coastal Protection                   ment as a solution to shoreline erosion problems.
                               Structures                                                  However, there are many issues which need to be
                                 Few issues along the Califomia coast are more             resolved prior to embarking on any large scale
                               complex, more poorly understood, or more divi-              nourishment project. The availability of large vol-
                               sive than the continued use of coastal protection           umes of sand of the appropriate size, the impacts
                               structures. At present there is no comprehensive            of removing the sand from the source area and
                               state policy defining the private or public role of         transporting it to the beach, and the magnitude
                               protective devices in geologically hazardous ar-            and distribution of costs affect the feasibility of
                               m. Local government policies and practices vary             such programs. Durability and longevity of nour-
                               widely. Many communities will not allow devel-              ished beaches is another concern. Due to the high
                               opment of a parcel if a coastal protection struc-           littoral drift rates along most of the California
                               ture is required to insure survival of the dwelling         coast, the life span of nourished beaches in most
                               during its design life. At the opposite end of the          locations is expected to be relatively shon. A
                               spectrum, some communities require that the                 recent study concluded that 18 percent of


                               134








                California's nourished beaches lasted less than          limited research and has funded some institu-
                one year, and 55 percent lasted only one to five         tional research in the past, the state has not
                years (Pilkey and Clayton 1987).                         allocated permanent funds for these efforts. As a
                State Agency Policies and Practices                      result, the agency works in a reactive and largely
                  In 1978, the California Secretary of Resources         ad-hoc mode, responding to individual requests
                promulgated a Shoreline Erosion Protection               as they are submitted yearly, rather than operating
                Policy to govern state agency activities in shore-       under a comprehensive program governed by
                line environments. This declaration provided both        clear and sound policy and explicit criteria for
                a clear description of the role of each department       establishing priorities.
                within the agency in dealing with the shoreline          Department of Parks and Recreation
                and a comprehensive set of policies which are as           The California Department of Parks and Rec-
                appropriate today as they were a decade ago. In          reation is responsible for managing over 2 10
                spite of this policy, there is considerable variation    miles of the state's 1, 100 miles of coastline.
                in the actual policies and practices of the indi-        There are 117 individual DPR units along the
                vidual agencies; in some cases, there is a notable       coast, each with an official designation (State
                lack of any clear policy direction. The policy hi-       Beach, Park, Reserve, etc.) that influences the
                erarchy governing these agencies extends down-           management, development, and operation of the
                ward from State Code, through commission-level           particular unit. The storms of 1978, 1980, 1982,
                policy, and finally down to departinent-level            and 1983 resulted in extensive damage to State
                policy, guidelines, in-house memorandums, etc.           Park facilities, requiring an expenditure of $4.8
                The vague or generalized wording of many such            million for repairs. Beach-level campgrounds,
                declarations, combined with the separation and           access roads, parking lots, stairways, restrooms,
                autonomy of the local district or regional offices       seawalls, and other support facilities were dam-
                of some agencies and the constant influence of           aged, rebuilt and, in a number of cases, dam-
                political figures, has led to many state projects        aged again.
                that are inconsistent with existing Coastal Act            Due to the costs involved in continual recon-
                policy. In the words of one state agency staff           struction in some of these hazardous locations, a
                member, "policy is only for staff, not decision          new coastal erosion policy was developed by the
                makers."                                                 department following the 1983 storms, with a
                   Two state agencies-the Department of Boat-            goal to "avoid construction of new permanent
                ing and Waterways and the Department of Parks            facilities in areas subject to coastal erosion, and to
                and Recreation-have substantial authority re-            promote the use of expendable or movable facili-
                garding the expenditure of state funds for shore-        ties where the expected useful life is limited due
                line erosion control. Brief summaries of these           to their location in erosion prone areas." 'Me
                agencies' practices follow.                              avoidance of hazardous areas or the retreat from
                Department of Boating and Waterways                      sites where repeated storm damage through either
                   The Department of Boating and Waterways               wave impact or shoreline erosion has taken place,
                responds to requests by local governments for            are logical approaches for an agency which is fo-
                technical and monetary assistance in shoreline           cussed primarily on providing recreational areas
                protection projects. Over the past 20 years the          for the public.
                agency has expended over $26 million on                     Despite this official policy, major reconstruc-
                projects involving shoreline protection and beach        ti.on of a seawall and beach level facilities at one
                                                                         site took place again, although there were seven
                nourishment, typically with a funding distribution
                of 75 percent state, 25 percent local. The depart-       prior episodes of destruction. This effort was
                ment cannot fund all of the requests received. It        clearly contrary to the established policy. There is
                has no overfiding policies governing either their        considerable uncertainty in the minds of some
                beach erosion-control program or their allocation        state staff as to the status of this policy and
                of funds. Although the department carries out            whether or not local staff are even aware of its
                                                                         existence. State staff also express considerable


                                                                                                                               135






                            cynicism with respect to the lack of enforcement         (2) Site-specific Geotechnical Studies
                            of state policy by decision-makers at all levels of         Consistent geologic and geotechnical report
                            government, observing that policy invariably             guidelines specifying both the scope and content
                            takes a back-seat to political pressure.                 of reports for all types of coastal hazard investiga-
                            California Coastal Zone Conservation                     tions should be required as a matter of state
                            Commission                                               policy. A process of peer review of these reports
                               The limited number of technical staff, the            by qualified professionals is needed in order to
                            heavy project review demands, and the advisory           ensure complete investigations, sound conclu-
                            nature of guidelines have combined to limit the          sions, and appropriate mitigation measures.
                            State Coastal Commission's role in coastal haz-          (3) Legal Issues Surrounding Coastal Hazard Li-
                            ard evaluation. As such, local governments have          ability
                            retained the primary responsibilities for setting           Geologic hazard disclosure statements and
                            and implementing standards governing develop-            deed posting of existing geologic and
                            ment in hazardous locations, although regional-          geotechnical reports relevant to specific parcels
                            level Coastal Commission staff frequently                should be required statewide. Local governments
                            provide technical assistance to local jurisdictions.     should receive state technical assistance in the
                               These concerns raise serious questions regard-        formal designation of coastal hazards and legal
                            ing the effectiveness of Califorriia's governance        assistance and support in instituting appropriate
                            of coastal hazards. There appears to be consider-        restrictions and regulations in areas of recognized
                            able variation in policies and practices within and      high geologic risk, thus reducing litigation that
                            among state agencies. Policy language is often so        can render the local government planning and
                            ambiguous as to permit the approval of virtually         regulatory process ineffective.
                            any project, and the consistent translation of           (4) Blufftop Development Policies
                            policy from the state to district or unit levels is         A minimum blufftop setback should be re-
                            also a problem.                                          quired for 0 new construction, and all recon-
                                                                                     struction or remodeling which increases the value
                            State Actions To Improve Coastal                         of the structure by more than 25 percent. This set-
                            Hazard Policies                                          back should be based on site-specific erosion
                              The California Legislature should take action          rates and a structural life of 100 years without re-
                            to improve the appropriateness and effectiveness         liance on a protective device. A minimum set-
                            of coastal hazard policies. Such actions should          back of 25 feet should be required, and the
                            require local governments and state agencies to          concept of a "rolling setback" that moves land-
                            make the policy changes described below.                 ward over time should be used in delineating this
                                                                                     setback.
                            Local Government Level                                   (5) Beach-level Development
                            (1) Coastal Hazard Identification, Evaluation,              Beach level development and reconstruction or
                            and Review                                               remodeling which increases the value of a struc-
                              Every local government making coastal land             ture by mom than 25 percent should be permitted
                            use decisions should have a comprehensive and            only when safety from wave impact and inunda-
                            accessible information base that is developed            tion throughout a projected 100-year lifetime of
                            through adequate scientific and technical studies.       the structure can be demonstrated without reli-
                            Each jurisdiction should designate special geo-          ance on a protective device.
                            logical hazard areas where detailed site-specific
                            studies are necessary. A comprehensive coastal           (6) Emergency Condition and Reconstruction
                            geologic hazards ordinance should be required            Policies
                            for every coastal jurisdiction with identified geo-         Definitive guidelines should be adopted to
                            logic hazards.                                           govern actions taken under postemergency condi-
                                                                                     tions, including a timetable for the removal of any



                            136







               materials emplaced for emergency protection.             should not attempt to fund all proposals for shore-
               Coastal jurisdictions must recognize hazardous           line protection and beach nourishment. Proposed
               conditions and woik towards reducing the need            new "hard" protective structures should receive
               for emergency permits by siting all new develop-         particularly close scrutiny and should be funded
               ment and reconstruction away from hazardous              only when compelling circumstances so warrant.
               locations. Reconstruction which increases the            Department of Parks and Recreation
               value of a structure by more than 25 percent, or            The practices of the Department of Parks and
               where storm or erosion damage is greater than 25         Recreation should reflect the agency's adopted
               percent of the value of the structure, should be         policy, which prohibits construction of new facili-
               subject to the same geologic hazard review and
               evaluation process for safety and long-term sta-         ties in areas subject to coastal erosion. Policies
               bility (including obtaining a Coastal Develop-           goven-ling construction, reconstruction, mainte-
               ment Permit) as any proposed new development.            nance and protection in hazardous shoreline areas
                                                                        should be applied uniformly at both the state and
               (7) Policies Goven-Ang Coastal Protection                local-unit levels.
               Structures
                  Proposed new shoreline development should             Coastal Zone Conservation Commission
               only be permitted if it is safe from coastal hazards        The technical and scientific responsibility for
               for 100 years without reliance on a protective de_       coastal geologic hazard evaluation should be
               vice. Alternatives to protective devices, for both       transferred from the Coastal Commission to the
               private and public projects, should be vigorously        California Division of Nfines and Geology as de-
               pursued. Hard protective structures should be per-       tailed below.
               mitted only when a complete environmental as-
               sessment can make the following findings: (1)            A Comprehensive State-Level Coastal
               historical erosion rates substantiate the need for a     Hazards Program
               solution; (2) the structure will not produce a sig-         Significant changes are needed in the policies
               nificant loss of public beach; (3) existing public       and regulations of the the State of California gov-
               access will not be reduced; (4) scenic values will
               not be significantly reduced on contiguous public        eming development in coastal hazard areas. An
               trust lands; and (5) the proposed structure is the       expansion and refinement of policies and prac-
               most acceptable and durable long-term solution.          tices is necessary in order to achieve a consistent
               Proposals for new protective devices should be           and effective response to the continuing pressure
               carefully reviewed by qualified professionals and        to develop in these areas. The marked inconsis-
               the effectiveness of any adjacent protective struc-      tencies among the local governments and state
               tures should be considered prior to granting per-        agencies that regulate development reflect a lack
               mits for new structures.                                 of state direction and reveal a heavy influence of
                                                                        local economics and politics.
               State Agencies                                              Through a process of hazard recognition and
               Department of Boating and Waterways                      evaluation and a subsequent standardized set of
                  The Department of Boating and Waterways               avoidance, mitigation or hazard reduction policies
               should establish clear priorities for shoreline pro-     incorporating the actions set forth above, the pri-
               tection projects, including a clarification of which     vate and public losses from future shoreline ero-
               projects are appropriate for state funding, which        sion, storm impact and sea level rise can be
               have high, moderate, or low priority, and which          significantly reduced. The objective is to reduce
               will not be funded. Evaluation criteria should           the number of people, as well as dwellings, struc-
               include (1) ownership of property being protected        tures, and utilities, both public and private, di-
               (private or public); (2) effectiveness and pro-          rectly exposed to the hazards of shoreline erosion,
               jected lifetime of proposed project; (3) options or      wave impact, and inundation. The Alquist-Priolo
               alternatives available; and (4) both short- and          Act, which established Special Studies Zones
               long-term environmental impacts. The state               along California's active faults, is an appropriate
                                                                        model to follow for the coastline.


                                                                                                                               137







                                Due to the lack of responsibility within any         Califoniia Coastal Zone Conservation Commis-
                            existing state agency for systematically evaluat-           sion, 1975. California Coastal Plan. San
                            ing shoreline hazards and recommending state-               Francisco, California.
                            wide policy, such authority should be vested             California Department of Navigation and Ocean
                            within the Califon-da Division of Mines and Ge-             Development, 1972. California Comprehen-
                            ology, an agency already charged with evaluating            sive Ocean Area Plan. Sacramento, California.
                            California's natural hazards and resources.              Fulton-Bemett, K. and Griggs, G.B., 1986.
                                The modest funding required to implement                Coastal Protection Structures and their Effec-
                            such a program along the shoreline would have a             tiveness. Joint Publication of the State of
                            high benefit-to-cost ratio. Initial investigations          California Department of Boating and Water-
                            would establish the general hazard or special               ways and the Institute of Marine Sciences at
                            studies zones which would then be delineated on             the University of California at Santa
                            official state maps. Any development or signifi-            Cruz. 48pp.
                            cant changes in land use proposed within these           Griggs, G.B., 1986. "Reconstruction or Reloca-
                            areas at the local government (private or public)           tion: Viable Approaches for Structures in
                            or state level would require complete geologic              Areas of High Coastal Erosion." Shore and
                            hazard investigations, report review by an inde-            Beach 54: 8-16.
                            pendent qualified professional, and appropriate          Griggs, G.B., 1987. "California's Retreating
                            setbacks and mitigation measures. Geologic re-              Shoreline: The State of the Problem." Proc.
                            port guidelines comparable to those outlined in             Coastal Zone '87. Seattle, Washington:
                                                                                        A.S.C.E. pp 1370-1383.
                            the Alquist-Priolo program and by the California
                            Division of Mines and Geology should also be             Griggs, G.B. and Savoy, L., 1985. Living with
                            adopted.                                                    the California Coast. Durham, North Carolina:
                                A reduction in both risk exposure and public            Duke University Press. 344pp.
                            and private economic losses from geologic haz-           Griggs, G.B., Pepper, J.E., and Jordan, M.E., in
                            ards in the coastal zone are objectives which need          preparation. California's Coastal Hazards: A
                            to be realized. The Coastal Act focussed on what            Critical Assessment of Existing Land Use
                            were deemed to be the critical issues of the time           Policies and Practices, Final Report to the
                            but was deficient in treating geologic hazards.             California Policy Seminar Program.
                            Although some local governments have been ef-            Habel, J.S. and Armstrong, G.A., 1977. Assess-
                            fective in dealing with coastal hazard issues, it is        merit and Atlas of Shoreline Erosion Along the
                            now time for a state-level program that provides a          Califorriia Coast. California Department of
                            consistent, efficient, and streamlined approach for         Navigation and Ocean Development. Sacra-
                            land use regulation in hazardous coastal areas.             mento, California.
                                                                                     Pilkey, O.H. and Clayton, T.D., 1987. "Beach
                                                                                        Replenishment: The National Solution?" Proc.
                            Acknowledgments                                             Coastal Zone '87. Seattle, Washington:
                                The research for this study was supported by a          A.S.C.E. pp 1408-1419.
                            grant from the California Policy Seminar Pro-            State of Califorriia, 1972, The California Coastal
                            gram, ajoint University of Califoniia/State Gov-            Zone Conservation Act of 1972 (Proposi-
                            emment Program.                                             tion 20).
                                                                                     State of California, 1976. California Coastal Act
                                                                                        of 1976 as amended January 1988. Public
                            References                                                  Resources Code, Division 20.
                            Burton, I., Kates, R.W., and White, G.F., 1978.          United States Army Corps of Engineers, 197 1.
                                The Environment as Hazard. New York:                    National Shoreline Study: California Regional
                                Oxford University Press.                                Inventory. South Pacific Division, San Fran-
                                                                                        cisco, California.





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                 WASHINGTON STATE COASTAL HAZARD                                                                                       PUBLIC POLICY

                                                                                                                                        0
                 INITIATIVES
                 Douglas J. Canning                                                                                                                 Lot
                                                                                                                                                     2
                 Shorelands and Coastal Zone Management Program, Washington Department ofEcology
                                                                                                                                                   3


                                                                           River jetty, at the entrance to Willapa Bay, and at         COASTAL
                 Introduction                                              Westport near the south jetty of Grays Harbor.              HAZARDS POLICY
                 The development of coastal hazards policy in                                                                          ISSUES ON THE
                 Washington State results from the state-local             There are growing concenis that the historic ac-            WEST COAST
                 partnership mandated in the Washington Shore-             cretion of the southwest beaches may not con-
                 line Management Act. The state law and regula-            tinue due to the trapping of sediment by dams on
                 tions set out broad goals and the means of                the Columbia River and the possible acceleration
                                                                           in sea level rise postulated with global warming
                 complying with those goals. Local governments             (Phipps 1990).
                 adopt Shoreline Master Programs that collec-                 The shorelines of Puget Sound consist largely
                 tively form the state's Shoreline Master Program.         of unconsolidated glacial materials that are vul-
                 The Department of Ecology has oversight author-           nerable to erosion. Keuler (1988) mapped erosion
                 ity to assure that local master programs are con-         patterns along various types of shoreline in north-
                 sistent with state law.                                   ern Puget Sound and measured erosion rates of
                    Currently, the Department of Ecology is ad-            about 5 to 30 centimeters (0. 1 to 1.0 feet) per
                 dressing three coastal hazard policy issues: ero-         year. The range of 6 to 9 centimeters (0.2 to 0.3
                 sion and landsliding, sea level rise, and                 feet) per year seems most common. The Coastal
                 incorporation of the public trust doctrine into           Zone Atlas (Ecology 1978) included a qualitative
                 management and permitting decisions.                      estimate of erosion along the entire Puget Sound
                                                                           shoreline and found over 30% of the shoreline to
                 Coastal Erosion Management                                be actively eroding. A much larger portion may
                    No comprehensive assessment of coastal ero-            be subject to more gradual or to episodic erosion.
                 sion has been completed for Washington State.                Rates of shoreline retreat are slow enough in
                 The rate of erosion along Washington's shoreline          most of Washington that little attention is paid to
                 is known to be highly variable. In some areas ero-        locating structures away from the shore. No local
                 sion is simply not a problem, whereas in other            governments regulate setbacks based on erosion
                                                                           rates (Canning 199 1 a). The common perception,
                 places erosion is relatively rapid. Erosion is rarely     however, is that the risk is greater than it truly is.
                 catastrophic and life threatening, but it can result      The general response to erosion in Puget Sound is
                 in losses of property. (Nowhere in Washington is          the armoring of the shoreline, primarily with
                 the rate of erosion as rapid and threatening as it        concrete bulkheads, although alternatives are
                 commonly is along portions of the Gulf and At-            recommended (Canning 199 1 b). Most local gov-
                 lantic coasts.)                                           ernment regulations conditionally permit shore-
                    Erosion in Washington falls into two basic cat-        line annoring to protect structures; this provision
                 egoties: beach erosion and bluff retreat. The             has often been misinterpreted to include pro-
                 former is often the result of a loss of sediment          tection of property. As of the mid- 1970s, rouglily
                 supply, whereas the other may be largely related          8% of the Puget Sound shoreline was armored
                 to the local geology.                                     (Downing 1983), largely in urban areas, but this
                    The southwestern coast of Washington con-              number has certainly increased in the last 15
                 sists of wide sand spits and large, protected estu-       years. The greatest increases have occurred along
                 aries. The beaches of Grays Harbor and Pacific            residential shorelines.
                 counties are largely accretional, although local-
                 ized erosion has occurred at the north Colurnbia



                                                                                                                                   139







                                Coastal landsliding is often considered to be a      associated with large-scale shoreline hardening,
                             simple coastal erosion problem. The geologic            as well as for addressing viable alternatives. A
                             sequence of sands and gravels intermixed with           programmatic EIS could also provide a firrn
                             clays and tills typical of Puget Sound bluffs is a      foundation for local govenunent decisions or
                             highly unstable combination. The intermediate           regulatory reform. We are seriously considering
                             sand and gravel unit is not stable, particularly        canying out the programmatic EIS as requested,
                             when saturated with water. It is also easily            our budget permitting.
                             eroded by waves or by surface runoff. Ground-              The policy issue we face is the balancing of
                             water concentrates at the base of the porous units,     the protection of private rights in real property
                             since it cannot pass downward into the underly-         with the protection of public rights in naturul re-
                             ing clays or tills. Groundwater seeps from bluff        source properties. Owners of upland properties
                             faces carrying material with it and undercutting        feel a strong need to protect their investments in
                             overlying materials. When the sand and gravel           land and buildings. Shoreline an-noring is com-
                             fails, the overlying Vashon Till also collapses.        mon even of properties little affected by erosion.
                                Over 30% of Puget Sound's shoreline is               Extensive shoreline annoring, however, is de-
                             mapped as unstable; in some counties the                stiuctive of the public resource properties in the
                             percentage is much higher (Downing 1983).               intertidal and shallow subtidal habitats. Juvenile
                             These unstable areas include many old                   pink and chum salmon require shoreline shallows
                             landslides, as well as many potential slides.           to escape predation on their migration out to sea.
                             Many of these old landslides have alread been           Pacific herring and surf smelt require intertidal
                                                                        !Y
                             built on, out of either ignorance or overconfi-         and subtidal habitats for spawning. Shoreline
                             dence. Where the geology can be mapped, the             annoring impinges upon these habitats and over
                             likelihood of landsliding can often be predicted.       the long term degrades them.
                             Landsliding can also be favored by improper
                             clearing and gruding practices and by poor              Sea Level Rise
                             drainage in upland areas.
                                Landsliding risk is greatest for development            Washington's sea level rise initiative began in
                             along the edge of unstable bluffs or at the base of     1988 when we first asked ourselves, "Is this a
                             these bluffs. Development on existing landslide         real issue for Washington State?" Clearly the an-
                             deposits is clearly hazardous.                          swer was yes, and for two reasons. First, the ex-
                                Concern has grown in the state about the cu-         isting rate of sea level rise, in conjunction with
                             mulative impacts of bulkheading on both the             subsidence within Puget Sound, is sufficient to
                             physical and biologic function of the shoreline.        explain the slight but chronic erosion of uncon-
                             Shorelands has an ongoing program in this area          solidated Puget Sound shorelines. Second, accel-
                             to address the effects of shoreline hardening           erated sea level rise due to global climate change
                             (Terich and Schwartz 1990), alternatives to             could have substantial effects on specific coastal
                             shoreline hardening (Tefich, Schwartz, and              locales.
                             Johannessen,1991a, 1991b), and the rate and                A Sea Level Rise Task Force was convened,
                             character of shoreline hardening.                       consisting primarily of state resource agencies.
                                During August 1991 the Department of Ecol-           The recommendations of the task force fell in
                             ogy received requests from the Thurston County          three basic areas: the need for information on the
                             and Mason County commissioners that the de-             effects of vertical land movement on relative sea
                             partment undertake the prepamfion of a program-         level rise; the need for more certain sea level rise
                             matic environmental impact statement (EIS) on           scenarios; and potential future policy issues. Po-
                             the cumulative effects of bulkheading and other         tential policy issues were identified as
                             forms of shoreline hardening.                                siting standards and protection altematives
                                We believe that a progimmatic EIS could be                for private and public coastal facilities and
                             a useful and educational process for assembling              developments.
                             and disseminating information on the problems


                             140







                   0 cleanup and closure standards for coastal          Tacoma by 2050, in Seattle by 2055, and in Fri-
                     solid and hazardous waste disposal sites,          day Harbor by 2067. Under this scenario, the up-
                     which would need to be inventoried,                lift at Neah Bay would delay occurrence of a 0.5
                     characterized, and mapped.                         meter rise until about 2080.
                   0 impacts on marine resources such as                   At present, existing sea level rise is causing or
                     wetlands and shallow-water habitats.               aggravating shoreline erosion and bluff land-
                   * seawater intrusion of coastal aquifers,            sliding. As noted above in the Coastal Erosion
                     especially where seawater intrusion is an          Management section, erosion and erosion man-
                     existing problem.                                  agement are currently issues of concern with
                                                                        coastal managers in state resource agencies and
                   Following the recommendations of the Sea             local planning departments. Over a period of
                Level Rise Task Force, in 1989 Shorelands               decades, accelerated sea level rise is expected to
                initiated a series of technical and policy studies      aggravate existing erosion and landsliding pro-
                and assessments. A study of vertical land move-         blems. Seawater intrusion of coastal aquifers,
                ments indicated that uplift along portions of           which is a problem on the islands of north and
                Washington's Pacific Ocean coast (up to 24 cen-         central Puget Sound and along Hood Canal due to
                timeters a century) would mitigate near term            groundwater withdrawals, will be aggravated.
                accelerated sea level rise, but that subsidence         Areas currently at risk of flooding will experience
                within Puget Sound (up to 24 centimeters a cen-         more frequent and more severe flooding; areas
                tury) would aggravate sea level rise (Shipman           just above the flood zone now will become sub-
                1989). An assessment of the state-of-the-               ject to flooding. Wetlands and possibly other low-
                knowledge, likely impacts, and potential policy         lying coastal areas will be subject to inundation.
                issues was prepared (Canning 1990). Research               The types of areas at risk are primarily uncon-
                into wetlands sedimentation and subsidence was          solidated shorelines, low-lying areas, coastal wet-
                carried out at three locations in northern Puget        lands, accreted shoreforms, interfidal and shallow
                Sound by Western Washington University (Beale           water habitats, and major river deltas. No quanti-
                1990). Results confirmed that sea level rise in         tative studies have been carried out to delineate
                Puget Sound has been consistent with global             the extent or degree of risk.
                averages ranging from 10 to 15 centimeters a               Unconsolidated shorelines include most Puget
                century.                                                Sound, Grays Harbor, Willapa Bay, and Colum-
                   In the near term, the flu-eat is moderate and is     bia estuary shorelines. The rocky shores of the
                caused by the existing rate of sea level rise (about    San Juan Islands are a notable exception. Uncon-
                12 centimeters a century) as mitigated or aggra-        solidated shorelines are susceptible to erosion.
                vated by regional vertical land movements. Along        The present long-term average erosion rates of a
                the Pacific Ocean coast, uplift exceeds the exist-      few tenths of a foot per year are expected to in-
                ing rate of sea level rise in the vicinity of Neah      crease with any acceleration in the rise of sea
                Bay and the Columbia River estuary, producing a         level.
                net relative sea level fall. Within Puget Sound            Low-lying areas will be threatened from stonn
                vertical land movement ranges from zero in the          surge, flooding, or inundation, depending on their
                San Juan Islands-Skagit Bay-Sequim area, to             elevation, the rate of acceleration, and the techni-
                about 24 centimeters a century at Tacoma. The           cal and fiscal feasibility of protection. Urban ar-
                maximum relative sea level rise is about 36 centi-      eas potentially threatened by storm surge,
                meters a century (1.2 feet a century) at Tacoma.        flooding, or inundation are typified by the central
                   Currently the generally accepted scenarios for       business district of Olympia, the state's capitol.
                accelerated sea level rise due to global climate        Thurston Regional Planning Council and the City
                change range between 0.5 meters and 1.5 to 2.0          of Olympia am nowcarrying out an assessment of
                meters by the year 2 100. If we take into account       the Olympia CBD under a Coastal Zone Manage-
                vertical land movement, a 1.0 meter acceleration        ment grant; the assessment report will be com-
                would result in a 0.5 meter sea level rise in           pleted by June 1992. In other developed


                                                                                                                             141







                               low-lying areas, investrnents in agricultural lands,          A Policy Alternatives Study to review and
                               public highways or air ports, residential real es-         evaluate existing legal authorities and potential
                               tate, or other facilities am at risk.                      policy response alternatives was carried out by
                                  Coastal wetlands will be threatened by erosion          Battelle's Human Affairs Research Centers under
                               or inundation. An assessment of selected Puget             contract to Shorelands (Klarin et al. 1990). The
                               Sound shorelines is being carried out by Holcomb           analytical portion of the study addresses regula-
                               Research Institute in cooperation with the Wash-           tory approaches, economic and market strategies,
                               ington Department of Ecology under a U.S. Envi-            and governmental programs for a variety of
                               ronmental Protection Agency grant; the final               issues:
                               project report is scheduled for publication by the            -  Wetlands protection and preservation
                               U.S. EPA in spring 1992.                                      0  Protection and preservation of shallow-
                                  Accreted shore forms (coastal barriers, sand                  water and estuarine habitats
                               spits, and so on) will be threatened by erosion,              *  Seawater intrusion
                               storm surge, flooding, or inundation. The princi-             -  Groundwater contamination
                               pal accreted shore forms have been inventoried                0  Beach, shoreline, and bluff erosion
                               and characterized (Shipman 199 1).                            *  Preserving public access and recreation
                                  Intertidal and shallow-water habitats will be at              opportunities
                               risk from a likely secondary effect of response to            0  Planning, permitting, and remediation of
                               sea level rise. As some shorelines become hard-                  facilities and infrastructure
                               ened (bulkheads, sea walls, riprap, etc.) to resist           0  Shoreline floodplain hazards management
                               erosion, the shoreline will become fixed in place,
                               and rising sea level will steadily lessen the extent          An assessment of the approaches of local gov-
                               of intertidal and shallow-water habitats, possibly         eniments to sea level rise response will be evalu-
                               eliminating intertidal habitat in some locations.          ated through the Coastal Zone Management Act
                               Intertidal and shallow-water habitats are impor-           Section 306 and 306A planning and construction
                               tant for the rearing and migration of juvenile             grants program. Beginning in Washington's Fis-
                               salmon, spawning of Pacific herring and surf               cal Year 1992 (July 1991 to June 1992), Section
                               smelt, and the life cycle of certain shellfish.            306 and 306A grant projects must be engineered
                                  Major river deltas will be subject to the same          and constructed for the existing rate of sea level
                               threats as low-lying areas and accreted shore              rise (including subsidence) and must include con-
                               forms. Additionally, the delta waters will be sub-         ceptual planning for accelerated sea level rise pre-
                               ject to salinity changes affecting the general ecol-       paredness (Shorelands and Coastal Zone
                               ogy. The major river deltas of greatest concern            Management Program 199 1). This type of ap-
                               are the Skagit, Snohomish, Puyallup, and                   proach to sea level rise preparedness is similar to
                               Nisqually on Puget Sound; the Chehalis on Grays            that of the San Francisco Bay Conservation and
                               Harbor, and the Willapa on Willapa. Bay. Other             Development Commission (Bay Plan Amend-
                               deltas wl-dch might be of concern are the Union,           ment No. 3-88 Concerning Sea Level Rise,
                               Skokomish, Hamma Hamma, Duckabush,                         Adopted January 5, 1989) and the U.S. Army
                               Dosewallips, and Quilcene on Hood Canal. River             Corps of Engineers (Circular No. 1105-2-186,
                               deltas and adjacent valley bottoms will be suscep-         Guidance on the Incorporation of Sea Level Rise
                               tible to seawater intrusion and a forcing of the           Possibilities in Feasibility Studies, Issued April
                               water table to higher elevations. This in turn will        21,1989).
                               lead to soil saturation and tertiary effects of de-
                               creased soil drainage and increased duration of            Public Trust Doctrine
                               flooding, increased corrosion of underground
                               tanks and pipes, the need to drain agricultural               The private rights and public use of tidelands
                               lands, and decreased effectiveness of sewage               and shorelands relating to the Public Trust Doc-
                               drain fields or possibly the need to install sewer-        trine is another issue of growing concern in
                               age systems.                                               Washington. In simple terms, the Public Trust


                               142







               Doctrine is a judicial statement of the state's re-      Trust Doctrine was recognized by name in a
               sponsibility to manage public property in the pub-       Washington State Supreme Court case. That rec-
               lic interest. The public property interests include      ognition was further reinforced by the Orion
               rights of navigation, fishing and shellfishing (both     Corp. v. State case. Furthermore, the court de-
               commercial and recreational), and by many inter-         clared that the Public Trust Doctrine had always
               pretations, the environmental quality necessary to       existed under Washington law even though not
               support fish and shellfish habitat in navigable and      explicitly cited.
               estuarine waters.                                           The implications for the public and for shore-
                  The ownership of all tidelands was transferred        line property owners can be interpreted in several
               to the state at the time of statehood under the          ways. One way would be that the permitting pro-
               equal footing doctrine of the U.S. Constitution,         cess established by the SMA is the means of pro-
               wherein each new state entering the union ob-            tecting the public's interest in the shoreline and
               tained status equal to the original thirteen states.     the tidelands, while allowing for necessary devel-
               Importantly, the original states followed English        opment on shoreline property. Part of the reason-
               common law, whereby the state govemments                 ing for this is the public review, comment, and
               held the tidelands in trust for all the people-the       appeals procedures that are built into the permit
               Public Trust Doctrine.                                   process. Altematively, the single family residence
                  Through the years, over 60% of Washington's           exemption from the permit process provided by
               inland marine water tidelands were sold to private       the SMA may be an inadequate protection of the
               upland owners (Conte 1982). Public use of shore-         public trust interest and could possibly be subject
               lines in Washington has traditionally respected          to court challenge. Third, allowing a bulkhead or
               private ownership of tidelands. Many private             other structure to be built which interferes with
               tideland owners have excluded the public by in-          the natural shoreline erosion and accretion pro-
               stalling "no trespassing" signs and occasionally         cess may also be an inadequate protection of the
               by physical threats. However, these actions may          Public Trust Doctrine's mandate to protect the
               be in violation of the Public Trust Doctrine. There      public interest in shorelands and shoreland re-
               is currently an emerging school of thought, sup-         sources.
               ported by recent court cases, that says that sales          Shorelands has sponsored an evaluation of the
               of tidelands never included all rights of property       implications of the Public Trust Doctrine for
               ownership and were subject to the Public Trust           coastal zone management in Washington State.
               Doctrine. The courts have held that a goveniment         This study is based upon a recently completed
               cannot relinquish its public trust responsibilities.     nationwide study (Connors, Laurence, Columbia,
               The act of selling tidelands does not negate the         Archer, and Bowen 1990). The Washington
               projections provided by the Public Tnist Doc-            analysis (Johnson, Goepple, Jansen, and Paschal
               trine. Therefore, in the case of tidelands as related    199 1) has just been completed.
               to the doctrine, the issue is, just what public rights
               do exist?
                  In a 1969 case, Wilbour v. Gallagher, the             Conclusions
               Washington State Supreme Court declared that                Coastal hazard initiatives in Washington State
               the public has the right to go where the navigable       center around erosion issues-long term and
               waters go, and ordered a fill in Lake Chelan             short term, real and perceived, physical and legal.
               removed. Wilbour v. Gallagher is considered to           As noted above, the central policy issue relates to
               be the legal basis for the state's Shoreline Man-        a balancing of public and private property rights.
               agement Act (SMA). At the time, the Supreme              Central to that balancing is a heightened aware-
               Court did not explicitly mention the Public Trust        ness of the state's responsibilities under the Pub-
               Doctrine.                                                lic Trust Doctrine.
                  In state courts the doctrine was largely unrec-
               ognized by name until the late 1980s. It was not
               until the case of Caminiti v. Boyle that the Public


                                                                                                                              143






                             References                                                Klarin, P., KM. Branch, M.J. Hershman, and
                                                                                           T.F. Grant 1990. Sea level rise policy alterna-
                             Beale, H. 1990. Relative rise in sea level during             tives study: Volume 1, Alternative policy
                                the past 5,000 years at six salt marshes in                responses for accelerated sea level rise and
                                northern Puget Sound, Washington.                          their implications; Volume 2, An analytical
                                Shorelands and Coastal Zone Management                     review of state and federal coastal manage-
                                Program, Washington Department of Ecology,                 ment systems and policy responses to sea level
                                Olympia.                                                   rise. Battelle Human Affairs Research Centers
                             Canning, D.J. 1991 a. Shoreline bluff and slope               for Shorelands and Coastal Zone Management
                                stability: management options. Shorelands and              Program, Department of Ecology, Olympia.
                                Coastal Zone Management Program, Wash-                 Phipps, J.B. 1990. Coastal accretion and erosion
                                ington Department of Ecology, Olympia.                     in southwest Washington: 1977-1987.
                             Canning, D.J. 199 lb. Marine shoreline erosion:               Shorelands and Coastal Zone Management
                                Structural property protection methods.                    Program, Washington Department of Ecology,
                                Shorelands and Coastal Zone Management                     Olympia.
                                Program, Washington Departmentof Ecology, Shipman, H. 1991. Coastal barriers and accreted
                                Olympia.                                                   landforms in Washington state: Inventory and
                             Canning, D.J. 1990. Sea level rise in Washington              characterization. Shorelands and Coastal Zone
                                state: state-of-the-knowledge, impacts, and                Management Program, Washington Depart-
                                potential policy issues. Shorelands and Coastal            ment of Ecology, Olympia.
                                Zone Management Program, Washington                    Shipman, H. 1989. Vertical land movements in
                                Department of Ecology, Olympia.                            coastal Washington: implications for relative
                             Connors, D.L., K. Laurence, S.C. Columbia, J.H.               sea level changes. Shorelands and Coastal
                                Archer, and R. Bowen. 1990. The National                   Zone Management Program, Washington
                                Public Trust study. Coastal States Organi-                 Department of Ecology, Olympia.
                                zation.                                                Shorelands and Coastal Zone Management
                             Conte, K.R. 1982. The disposition of tidelands                Program. 199 1. Sea level rise planning,
                                and shorelands: Washington state policy,                   engineering, and construction policies for
                                1889-1982. Unpublished master's thesis. The                Shorelands-funded projects. Shorelands and
                                Evergreen State College, Olympia, Wash-                    Coastal Zone Management Program, Wash-
                                ington.                                                    ington Department of Ecology, Olympia.
                             Downing, J. 1983. The coast of Puget Sound: its           Terich, T.A., and M.L. Schwartz. 1990. The
                                processes and development. Washington Sea                  effect of seawalls and other hard erosion
                                Grant University of Washington Press,                      structures upon beaches: an annotated bibliog-
                                Seattle.                                                   raphy. Shorelands and Coastal Zone Manage-
                             Ecology, Washington State Department of. 1978.                ment Program, Washington Department of
                                Coastal Zone Atlas of Washington (several                  Ecology, Olympia.
                                volumes).                                              Terich, T.A., M.L. Schwartz, and J. Johannessen.
                             Johnson, R.W., C. Goepple, D. Jansen, and R.                  1991 a. Annotated bibliography of beach
                                Paschal. 199 1. The public trust doctrine and              nourishment literature, with applicability to
                                coastal zone management in Washington state.               Puget Sound and summary, guidelines, and
                                Shorelands and Coastal Zone Management                     methodology. Shorelands and Coastal Zone
                                Program, Washington Department of Ecology,                 Management Program, Washington Depart-
                                Olympia.                                                   ment of Ecology, Olympia.
                             Keuler, R.F. 1988. Map showing coastal erosion,           Terich, T.A., M.L. Schwartz, and J. Johannessen.
                                sediment supply, and longshore transport in                1991b. Annotated bibliography of vegetative
                                the Port Townsend 30- by 60-minute quad-                   erosion control literature. Shorelands and
                                rangle, Puget Sound Region, Washington.                    Coastal Zone Management Program, Wash-
                                Map 1198-E, Miscellaneous Investigations                   ington Department of Ecology, Olympia.
                                Series, U.S. Geological Survey.



                             144






               OCEAN SHORE PROTECTION POLICY AND                                                                                  PUBLIC POLICY
               PRACTICES IN OREGON
                                                                                                                                  0
               James W. Good                                                                                                                  Lot
                                                                                                                                               2
               Coastal Resources Specialist, Extension Sea Grant Program                                                          Z
               College of Oceanic and Atmospheric Science, Oregon State University
                                                                                                                                              3


                                                                                                                                 COASTAL
                                                                                                                                 HAZARDS POLICY
               Introduction                                               As pressure increases for coastal development,         ISSUES ON THE
                                                                        the more hazardous sites avoided earlier fill in         WEST COAST
               The Oregon coast is renowned for its rocky               with houses, motels, and condominiums. Also,
               shores, rugged beauty, and accessible, uncrowded         earlier development along much of the coast be-
               beaches. Long, gently sloping beaches backed by          comes threatened as the shoreline gradually re-
               cliffs front much of the coast, interrupted only by      cedes. Episodic erosional events and other
               rocky basalt headlands that extend into the sea.         chronic hazards increasingly take their toll on this
               Steep-faced pocket beaches nestle within short           development. The response to these hazards has
               stretches of rocky coastline. Barrier sand spits         generally been to construct riprap revetments,
               with dune complexes enclose the estuaries of             seawalls, and bulkheads that are designed to fend
               more than a dozen coastal rivers. Other beaches          off waves, stabilize cliffs, and retain the
               form the trailing edge of landward-migrating             shoreland (see Kraus and McDougal, this vol-
               dune sheets.                                             ume). As more development occurs adjacent to
                  These ocean beaches are also public recreation        the beach, normal episodes of erosion create a
               areas by virtue of customary public use, far-            demand for more and more structures. These de-
               sighted legislation early in the century, and a sub-     velopment and shore protection practices, in turn,
               sequent series of laws that culminated in the            have raised questions about the effectiveness of
               historic 1967 Beach Bill. Though the path that led       Oregon's coastal management policies-policies
               to the preservation of public beach rights was           that were designed to protect the scenic values,
               marked with controversy-numerous legislative             recreational qualities, and accessibility of Oregon
               battles, landmark court cases, public initiative pe-     beaches; control development in hazardous areas;
               titions, and media blitzes-today we enjoy free           and promote nonstructural alternatives to revet-
               use of both the wet and dry sand portions of Or-         ments, seawalls, and other shoreline armoring.
               egon beaches, With an unparalleled system of             These concerns have been magnified by research
               state parks, waysides, and other access points           which suggests that engineering solutions to
               along the shore, these beaches are among the             coastal hazards sometimes lead to more prob-
               most accessible in the country.                          lems, including accelerated erosion of the beach
                  The Oregon coast is also one of the most dy-          and adjacent properties, loss of cliff-supplied
               namic in the world (see Komar, this volume). Se-         sand to the beach system, and gradual beach nar-
               vere winter storms, large waves, strong tides and        rowing in the face of sea level rise.
               nearshore currents, and rain and high winds cut             In this paper, I examine the effectiveness of
               into beaches and dunes. They undermine and bat-          Oregon's coastal management policies designed
               ter sea cliffs, causing slumping and slides, and         to mitigate the impacts of natural hazards on pub-
               flood low-lying coastal lands. In recent years, the      lic beach resources and private oceanfront devel-
               vulnerability of the coast to large, locally gener-      opment. I first outline relevant laws, policies, and
               ated earthquakes and tsunamis has become                 decision-making processes. I then examine and
               widely accepted in the scientific community, add-        evaluate the implementation of these policies,
               ing the threat of catastrophic hazards to the reality    based on a Sea Grant-sponsored case study of
               of the chronic ones we experience (see Madin,            shore protection and land use decisions along the
               this volume).                                            16-mile long Siletz littoral cell on the central


                                                                                                                             145







                            coast (Good 1992). Finally, I describe the strat-        hazards management. Goal 7, Natural Hazards,
                            egy being used by state coastal managers to im-          mandates that development subject to natural
                            prove the policy basis for mitigating natural            hazards not be located in known areas of natural
                            hazards on the Oregon coast.                             hazards without appropriate safeguards. Goal 17,
                                                                                     the Coastal Shorelands Goal, requires that LCPs
                                                                                     consider geologic and hydrologic hazards along
                            Coastal Natural Hazards Management                       the ocean shorelands. When problems of erosion
                            in Oregon                                                or flooding arise, preference must be given to
                               Local, state, and federal agencies each have          land use management practices and nonstructural
                            programs and policies related to the management          erosion controls. Goal 18, Beaches and Dunes,
                            of natural hazards along the Oregon coast. These         prohibits development on hazardous dune and
                            progrums and policies are summarized by func-            interdune lands and prohibits breaching of
                            tion and govenunental level in table 1. Three of         foreduries except in certain unusual circum-
                            the functions-infonnation and mapping, devel-            stances. Development on more stable dunelands
                            opment planning and siting, and shore protec-            requires findings that such development is ad-
                            tion-are discussed in more detail below. The             equately protected from erosion and other
                            state and local authorities listed are part of           hazards.
                            Oregon's coastal management program.                        Cities and counties were required to address
                            Hazards Research, Information, and Mapping               Statewide Planning Goals in their LCPs, which
                               The principal state agency for hazards re-            had to be reviewed and approved by the state. All
                            search, mapping, and technical assistance is the         coastal jurisdictions completed their initial round
                            Oregon Department of Geology and Mineral In-             of planning in the early 1980s and have state-ac-
                            dustries (DOGAMI). Much of the funding for               knowledged LCPs and implementing ordinances.
                            DOGANH research and hazard assessment comes              Specific LCP provisions for regulating develop-
                            from the U.S. Geological Survey (USGS), the              ment in hazardous oceanfront areas vary. All
                            Fedeml Emergency Management Agency                       counties have required construction setbacks, ei-
                            (FEMA), and other fedeml agencies. Also con-             ther fixed or variable. Some require geologic
                                                                                     hazard reports from a registered geologist or en-
                            thbuting to our understanding of coastal pro-
                            cesses and their influence on shorelines has been        gmeer, and some use overlay ordinances and
                            Sea Gmnt and other federally sponsored research          other provisions. However, there are few stan-
                            carried out at Oregon State University, the Uni-         dardized hazard mitigation provisions in the
                            versity of Oregon, and Portland State University.        plans and some are more effective than others.
                               The state coastal management agency, the De-             The federal govemment gets involved in land
                            partment of Land Conservation and Develop-               use management indirectly through provisions of
                            ment (DLCD), prescribes hazards inventory                the National Flood Insurance Progmm (NFIP)
                            standards for local govemment plans. Local gov-          (42 USC4001), administered by local govem-
                            ernments prepared hazard inventories in the late         ments through the Federal Emergency
                                                                                     Management Agency (FEMA). The Upton Jones
                            1970s or early 1980s as part of their comprehen-         provision of the law, passed in 1987, authorizes
                            sive planning process (see, for example, Lincoln         advance payment for relocation or demolition of
                            County Hazard Inventory [RNKR Associates                 any stiuctum that is covered by a cuffent NFIP
                            1978]). However, much of the information used            policy and that is subject to imminent collapse
                            for the inventories was general and has proven to        because of erosion. However, this provision has
                            be of limited use at the level of detailed site-de-      not yet been applied in Oregon and it is not likely
                            velopment.                                               to be an important management tool. Most of the
                            Planning and Siting of Development                       erosion-related property loss is for bluff-top areas
                               Oregon's statewide land use planning program          where residents do not have federal flood
                            includes hazard-related planning goals used by           insurance.
                            local goverriments to develop local comprehen-
                            sive plans (LCPs). Three goals apply directly to

                            146











                     GOVERNMENTAL                 FEDERAL                      STATE                       LOCAL
                     FUNCTION                     GOVERNMENT                   GOVERNMENT                  GOVERNMENT



                     Research, technical          0 US Geological Survey       N Dept. of Geology and      0 Local Comprehensive
                     information, and             (USGS)-hazards               Mineral Industries          Plan (LCP)-hazards
                     mapping                      E Federal Emergency          (DOGANH)-hazards            inventory and maps
                                                  Management Agency            info and mapping
                                                  (FEMA)-flood and             E Dept. of Land
                                                  erosion hazards              Conservation and
                                                  0 Corps of Engineers         Development (DLCD)-
                                                  (COE)-erosion hazards        hazards inventory
                                                                               standards
                                                                               N Universities/Sea
                                                                               Grant-research



                     Planning and siting of       E FEMA-National              0 DLCD statewide            0 State-approved LCP
                     development                  Flood Insurance              planning standards-         with natural hazards,
                                                  Program (NFIP)               Goal 7: Natural Hazards     shorelands, beaches, and         Table 1.
                                                                               Goal 17: Coastal            dunes elements; local            Governmental
                                                                               Shorelands                  subdivision, zoning, and         functions and
                                                                               Goal 18: Beaches and        flood damage prevention          agencies or
                                                                               Dunes                       ordinances                       authoritiesfor
                                                                                                                                            coastal natural
                                                                                                                                            hazards
                     Design and building          0 FEMA coastal and           0 State Building Code       0 Local building code            managetnent in
                     criteria                     flood construction           Agency-building             administration-city and          Oregon.
                                                  standards                    standards                   county


                     Shore protection             0 COE Nationwide             N State Parks and           E LCP and development
                                                  Permit No. 13-bank           Recreation Department       ordinances (provisions
                                                  stabilization                (SPRD): Beach Law-          vary)
                                                                               regulates shore
                                                                               protection structures
                                                                               N Division of State
                                                                               Lands (DSL):
                                                                               Removal/Fill Law-
                                                                               regulates revetments and
                                                                               fill



                     Emergency planning           N FEMA                       0 Emergency                 0 County emergency
                     and response                                              Management Division         services
                                                                               (EMDY-disaster
                                                                               response and planning



                 Shore Protection                                           Recreation Department (SPRD) and the Division
                     The installation of shore protection structures        of State Lands (DSQ, respectively. The emphasis
                 (SPSs) along the oceanfront is regulated by two            in both laws is on protecting public beach tights:
                 state laws: the Beach Law (ORS 390.605-                    recreation values and scenic and aesthetic quali-
                 390.770) and the Removal/Fill Law (ORS                     ties, and safe public access to and along the
                 196.800-196.990). These laws are administered              beach. Both agencies regulate the riprap revet-
                 as a joint pen-nit program by the State Parks and          ments and seawalls installed along the shore to



                                                                                                                                  147







                              control erosion and bluff slumping, though their              property, and long-term or recurring Costs be
                              jurisdictions differ somewhat. SPRD regulates all             minimized. SPRD and DSL have incorporated
                              types and sizes of structures, but their geographic           these standards into their own regulations.
                              jurisdiction is limited to structtims that extend                The U.S. Army Corps of Engineers (COE)
                              west of a beach zone line (BZL) that was sur-                 regulates installation of SPSs under section 10 of
                              veyed in 1967, just after the Beach Law was                   the Rivers and Harbors Act of 1899 and section
                              passed. DSL, on the other hand, only regulates                404 of the Clean Water Act (P.L. 95-217). The
                              structures involving 50 cubic yards or more of                Portland District COE issued a new nationwide
                              material, but their geographic jurisdiction is not            permit for "bank stabilization" (N)NT 13), with
                              fixed and extends to the upland vegetation line.              regional conditions for Oregon, effective Febru-
                              Oregon's coastal planning Goal 18 for Beaches                 ary 14, 1992. It replaced a similar 1986 regional
                              and Dunes also plays a role in regulating shore               permit. NWP 13 effectively removes the Corps
                              protection. The goal prohibits beachfront protec-             from the majority of day-to-day shore-protection
                              tive structures in areas that were not "developed"            decision making.
                              on January 1, 1977. Development is defined as
                              houses, commercial and industrial buildings, and              Policy Implementation Effectiveness
                              vacant subdivision lots that are physically im-
                              proved through construction of streets and provi-                In 1988, with funding from Oregon Sea Grant
                              sion of utilities to the lot, or areas where special          and assistance from several state agencies and
                              exceptions have been approved. For SPSs, the                  local governments, I initiated an evaluation of the
                              goal also requires that visual impacts must be                implementation of existing policy for managing
                              minimized, necessary access to the beach be                   development and shore protection along the
                              maintained, and negative impacts on adjacent                  oceanfront (Good 1992). The objectives of the
                                                                                                        study were (1) to determine if the goals
                                                                                                        and objectives of Oregon's shoreline
                                                                 V
                                                                                                        management laws, programs, and regu-
                                                                                                        lations are being achieved; (2) to exam-
                                            Cascade     V:
                                              Head
                                                                                                        ine the validity of the underlying
                                                                                                        scientific and management principles
                                                                         Salmon R.                      on which these laws, programs, and
                                            Roads End                                                   regulations were based; and (3) to pro-
                                                                                                        vide those who make and carry out
                                                              .-Devils Lake                             ocean shoreline management policy
      Figure 1. Silelz                                                                                  with specific suggestions for improving
                                              Lincoln                                                   policy and policy implementation.
      littoral cell: policy      (1)            City        Iver
      implenwidafion                                                                                       The principal focus of the study was
      study area.                                                                                       on the state laws and policies and LCPs
                                                                                 OREGON                 that make up Oregon's beachfront
                                             Siletz      ...                                            41management regime." Policy objec-
                                               Spit        Site fz Bay                                  tives from each law or policy were
                                        Gleneden                SilelzR.                                identified and synthesized into a single
                                           Beach                                                        set of shore protection and land use
                                         Lincoln     Schoolhouse Cr                N                    policy objectives. For each objective,
                                         Beach           Fogarty                                        possible measures or indicators of
                                  Fishing Rock            Creek                                         policy achievement were identified.
                              Government                                    0      km      5            Because of the long history of develop
                                  Point        F_
                                                                                                        ment there, the Siletz littoral cell was
                                                                          0        mi       4
                                                                                                        selected for the case study (figuir, 1).
                                                                                                                                       -devement of
                                                                                                        Data needs to evaluate acl



                              148






                 policy objectives were identified, a Siletz cell            Implementation Effectiveness of Oceanfront
                 geographic information system (GIS) was devel-              Development Policies
                 oped that incorporated this data on a tax lot by tax           One of the principal findings of this evaluation
                 lot basis, and the data were collected and entered          study is that in the Siletz littoral cell, there is a
                 into the GIS. A set of queries related to the policy        strong linkage between local land use decisions
                 objectives were developed and performed. The                and the demand for hard SPSs. These structures,
                 results, summarized below, represent the first de-          as discussed later, are cause for concern because
                 tailed assessment of how well key policy objec-             of adverse short- and long-term impacts on recre-
                 fives in Oregon's shore protection and land use             ational and scenic values, public access, and natu-
                 laws are being achieved.                                    ral replenishment of beach sand from sea cliff
                 Hazard-related Policy Goals and Objectives                  erosion.
                    Three fundamental goals are central to the                  There are a number of underlying reasons for
                 suite of laws and rules that constitute Oregon's            this linkage between land use decisions and SPS
                 beachfront "management regime." They are                    demand. First, despite the fact that Oregon has
                                                                             one of the most far-sighted set of state land use
                    1) to protect the beach for public recreational          policies in the United States (DeGrove 1984), in-
                      use and enjoyment;                                     cluding ffiree land use goals that focus on natural
                    2) to conserve, protect, and where appropri-             hazards, the hazard management strategies actu-
                      ate, develop or restore oceanfront lands;              ally employed by landowners depend more on
                      and                                                    structural mitigation than on hazard avoidance.
                    3) to protect human life and property from               Along the Siletz cell oceanfront, the result has
                      natural or human-caused hazards.                       been the proliferation of SPSs.
                                                                                This connection between land use and SPSs is
                    The more specific policy objectives in these             well understood by planners and others close to
                 laws and rules that link decisions with goal                the decision-making process and is supported by
                 achievement are summarized in table 2. These                a variety of evidence. For example, oceariftont
                 policy objectives are not the exact language of             construction setbacks for new buildings, whether
                 any single statute or rule, but are composite state-        they follow county or city guidelines or are based
                 ments from all the statutes and rules examined.             on consultant recommendations, are not effective
                 Measures or indicators of policy achievement are            hazard-avoidance mechanisms. In the Siletz cell,
                 also listed in table 2. These are the specific quali-       where new construction building setbacks met the
                 tative or quantitative data or evidence needed to           minimum requirements in the county/city hazard
                 determine whether or not local and state decisions          inventory, 40% of the sites later required SPSs to
                 am actually consistent with policies. The results           mitigate erosion hazards (table 3). Where county/
                 and conclusions reported here are based largely             city setbacks were not followed (usually smaller
                 on data and evidence from queries of the Siletz             consultant-recommended setbacks were substi-
                 littoral cell GIS and database.                             tuted), 38% later required SPSs. Clearly, neither
                 Are Policy Goals and Objectives Being                       county/city nor consultant setback procedures
                 Achieved?                                                   work well in limiting the demand for hard SPSs.
                    The policy goals outlined above and the objec-              The demand for structures is also increased by
                 tives in table 2 are implemented primarily                  local policies that sometimes require a property
                 through local land use and related administrative           owner to install a hard SPS in order to get a build-
                 decisions and thmugh shore protection decisions             ing permit. This is because a large number of va-
                 made at the state level. Examination of the out-            cant oceanfront lots are very shallow and virtually
                 comes and impacts of decisions made by local                unbuildable without an erosion-prevention struc-
                 governments and state agencies since the incep-             ture. Because subdivision and lot partition rules
                 tion of the programs, as well as processes used to          do not sufficiently factor in natural hazard con-
                 arrive at decisions, provides useful information            cerns along the oceanfront, lots with too little
                 for evaluating "implementation success." Some               depth continue to be created.
                 of these findings are outlined below.

                                                                                                                                       149








                                           OBJECTIVE'                                  MEASURE OR INDICATOR OF POLICY
                                                                                                    ACHIEVEMENT


                        1. Regulate the installation of SPSs                    a) process established and used to regulate the
                                                                                installation of SPSs

                                                                                b) numbers, types, and locations of regulated and
                                                                                unregulated SPSs constructed since 1967 (Beach Law)
                                                                                and 1976 (R/F Law)


                        2. Prohibit hard SPSs for property "developed"          a) process established and used to prohibit hard SPSs
                        after January 1, 1977                                   for property "developed" after January 1, 1977

                                                                                b) numbers, locations, and situations where SPSs were
                                                                                permitted, but development did not exist on January 1,
                                                                                1977



                        3. SPS permits shall not be approved unless             a) process established and used to determine
                        compatible with local comprehensive plans (LCPs)        compatibility of SPS proposals with LCP

                                                                                b) numbers, conditions, situations where SPSs
                                                                                permitted, but LCP compatibility not determined


                        4. Demonstrate the need and justification for shore     a) process established and criteria used to determine
                        protection                                              when a hazard exists and if a shore protection solution
                                                                                is warranted

                                                                                b) the need or justification for approved and denied
                                                                                shore protection permits as reported in findings; or
                                                                                actual physical or other evidence of need

                                                                                c) SPS application approval or denial decisions

                                                                                d) SPS application decisions on vacant parcels


                        5. Examine and, if reasonable, use alternatives to      a) processes are established and used to examine and
                        hard SPSs, including hazard avoidance in land use       consider land use management and nonstructural
                        and administrative decisions                            alternatives to hard SPSs


                                                                                b) numbers and locations of parcels where new
                                                                                development did or did not comply with required


                        Objectives were synthesized from policy language in the following statutes and administrative rules:

                        Beach Law (ORS 390.605-390.770)
                        Beach Improvement Standards (OAR 736-20-003 to 736-20-035)
                        Removal/Fill Law (ORS 196.800-196.990)
                        Removal/Fill. Administrative Rules (OAR 141-85-005 to 141-85-090)
                        Comprehensive Land Use Planning Law (ORS 197)
                        LCDC Goal 7, Areas Subject to Natural Hazards and Disasters (OAR 660-15-000)
                        LCDC Goal 17, Coastal Shorelands (OAR 660-15-010)
                        LCDC Goal 18, Beaches and Dunes (OAR 660-15-010)


                   Table 2. Oregon's beachfront developnwnt and protection policy objectives and nwasures or indicators ofpolicy achievetneni.



                           150









                                                                              hazard avoidance setback, and subsequent SPS needed
                                                                              for both categories

                                                                              c) numbers and locations of parcels that used or did not
                                                                              use relocation as a nonstructural alternative to hard SPS,
                                                                              and the potential for future use of this technique

                                                                              d) numbers, instances where other alternatives to SPSs
                                                                              have been used to mitigate hazards, or, for issued
                                                                              permits, evidence that such alternatives were not
                                                                              feasible



                     6. Before issuing permits, evaluate, avoid, and          a) process established and used for evaluating, avoiding,
                     minimize the individual impacts of permitted SPSs        and minimizing impacts of each proposed SPS; and for
                     on public access and recreation use; visual and          establishing and enforcing permit conditions
                     scenic resources; beach and adjacent land erosion;
                     public safety; other cultural and natural values and     b) where SPSs interrupt or destroy public access,
                     resources.                                               affected access ways to the beach are retained or
                                                                              replaced; where SPSs encroach on the public beach,
                                                                              lateral access is maintained; instances where SPSs
                                                                              installed at or adjacent to state parks, waysides, or
                                                                              public access points

                                                                              c) qualitative assessment of visual and scenic impacts of
                                                                              individual SPSs


                                                                              d) the design (and construction) of SPSs (size, scale,
                                                                              materials, shape, placement, lateral tie-in) is consistent
                                                                              with hazard and need; encroachment of individual SPSs
                                                                              on public beach; instances, situations where prohibited
                                                                              materials used to build SPSs


                                                                              e) evidence of SPS-induced beach or adjacent property
                                                                              erosion

                                                                              f) siting of SPSs with respect to historical and
                                                                              archaeological sites

                                                                              g) siting of SPSs with respect to threatened or
                                                                              endangered species habitat or other valuable wildlife
                                                                              habitats



                     7-Before issuing permits, evaluate, avoid, and           a) process established and used for evaluating, avoiding,
                     minimize the long-term, recurring, and cumulative        and minimizing cumulative impacts of SPSs
                     impacts of SPSs on public access and recreation
                     use, visual and scenic resources, beach and adjacent     b) cumulative length of SPSs installed along the
                     land erosion, public safety, and other cultural and      beachfront by year, type, and landform
                     natural values and resources.
                                                                              c) numbers, degree, and area of SPS encroachment on
                                                                              beach (as compared to beach area available) and effects
                                                                              on lateral access and recreational use


                                                                              d) cumulative loss of sand supply to the beach due to
                                                                              hard SPS installation along sea cliffs





                Table 2 cora.




                                                                                                                                151







                                                                                                           relatively uncoordinated planning for
        Table 3.                                                    LOTS                    SPS            beachfront areas. Virtually every foot
        Construction                                           DEVELOPED             NEEDED                of private beachfront land in the Siletz
        setbacks and                                                                 LATER                 cell is zoned for residential or commer-
        subsequent needfor
        shore protection              County/city setback             12                    5(40%)         cial development, with little regard for
        structures, Siletz            followed                                                             hazards. There are also few effective
        litioral cell, 1977-                                                                               controls on development practices that
        1991.                         County/city setback             47                    18(38%)
                                      not followed                                                         threaten the values, resources, and even
                                                                                                           long-term viability of the adjacent pub-
                                                                                                           lic beach. Little or no regard is given to
                                                                                                           beach stability factors or wave run-up
                                    Structural hazard mitigation is also promoted              and erosion potential when development is
                                by interpretations of planning goal language. For              planned. Finally, plans for adjacent jurisdictions
                                example, Goal 7 states that hazardous sites shall              within the same littoral cell are uncoordinated
                                not be developed without "appropriate safe-                    with respect to hazards.
                                guards." Local land use policy, approved by the                Implementation Effectiveness of Shore Protec-
                                state planning agency, interprets this language to             tion Policies
                                mean "adequate safeguards." And hard structures                   The oceanfront dunes and sea cliffs along the
                                are usually deemed "more adequate" than                        Siletz, cell shoreline are the most intensively de-
                                nonstructural mitigation. VAiile this outcome is               veloped along the Oregon coast-70% of its
                                not inconsistent with the hazard-related land use              nearly 900 buildable oceanfront lots are devel-
                                goal that focuses on the need to protect life and              oped. It is also one of the most erosion-prone ar-
                                property, it conflicts with the beach protection               eas along the coast (Shih 1992). As such, the cell
                                goal. The net result is more SPSs. Other policy
                                language that implicitly seeks to promote avoid-               represents a worst-case scenano in terms of de-
                                ance of hazards and avoidance of hard SPSs                     velopment intensity and potential demand for
                                C'Iand use management practices and                            SPSs. Given this situation, how well has the shore
                                nonstructural solutions ... shall be preferred") is            protection decision-making process worked in the
                                relegated to secondary status.                                 past? What have been the impacts or outcomes of
                                    The "hard structure solution" is further institu-          shore protection decisions? And what might be
                                tionalized by the largely uncritical acceptance by             done to improve the process to better achieve ex-
                                local officials of required geotechnical site reports          isting and possibly more informed policy goals?
                                that are based on variable standards and am not                   Along the Siletz littoral cell, the shomline is
                                subject to quality assurance measures or scrutiny              gradually being hardened with SPSs, mostly large
                                by peers. Revetments and seawalls have simply                  riprap revetments and low concrete seawalls (fig-
                                become the nonn. And, as one permit admirdstra-                ure 2). Of the 14 miles of beachfront shoreline,
                                tor put it, "revetments beget revetments."                     6.8 miles (49%) have seawalls or revetments in-
                                    Another reason land use practices are driving              stalled (figure 3). Figure 3 also illustrates the
                                the demand for SPSs has to do with where the                   clear relationship between SPS construction ac-
                                decision-making responsibility lies-almost                     tivity and the periodic El Niflos that bring short-
                                solely in the hands of local officials. There is a             term elevated sea levels, major storms, and
                                great deal of pressure on these officials to encour-           erosion. Because strong or very strong El Nifios
                                age and facilitate growth. Access to the local de-             occur on average every 8.5 years (Quinn et al.
                                velopment decision-making process by state                     1987), these severe erosion episodes and the
                                                                                               gradual armoring of developed and developing
                                agencies with broader or somewhat different mis-               coastlines are likely to continue.
                                sions is often nonexistent (in the case of local ad-              The starting point for most discussions about
                                ministrative decisions) or limited and costly                  shore protection measures that can be taken to
                                (through the land use decision appeals process).               mitigate actual or perceived hazards is the SPRD/
                                    Another contributor to problems of oceanfront              DSL joint permit process. With some exceptions,
                                development siting with respect to hazards is the

                                152







                       the shore protection process in
                       Oregon is basically a reactive
                       one-property owners, or their
                       consultants or contractors, fill out
                       and submit a joint SPS permit
                       application.                                                                                                                                                        Figure 2. Riprap
                           A first observation about the                                                                                                                                   revelments extend
                       permit process is that it has a                                                                                                                                     out on the public
                                                                                                                                                                                           beach at many
                       number of jurisdictional gaps and                                                                                                                                   points along
                       overlaps that limit its effective-                                                                                                                                  Gleneden Beach.
                       ness and create needless duplica-
                       tion of effort. Some of these gaps
                       become apparent in a perusal of
                       the governmental functions and
                       responsibilifies for shore pro-
                       tection outlined in table 4.
                       Others become evident from
                       queries of the Siletz cell GIS.                             LENGTH IN MILES
                       For example, as a result of                               8-                                                                                                        Figure 3.
                       jurisdictional gaps in SPS                                7-                                                                                          ...           Cumulative and
                       regulation, 3 of 10 ocean-                                6-     BEACHFRONT           -I.NC.ELL -- 14..0 ... MI                                    .......          year-to-year length
                                                                                       CUMULATIVE SPSs         6.8 MI (49%)                                                                of shore protection
                       front SPSs built since 1967                               5 ...         ...           .......                 . .... .... .    .....             . . .....          structures

                                                                                 4
                       in the Siletz cell have not re-                                                                                               .............     ...........         constructed in the
                       quired a state permit (table 5                                                                                                                                      Silelz littoral cell
                                                                                 3 -                                                                              .......                  (<1967-1991) and
                       and figure 4). Almost 50% of                              2                                                                                           ...           the relationship to
                       these SPSs were built east of                                                                                                                                       the moderate (M),
                                                                                 1-                          S          M  ...... .. .. ... VS                                             strong (S), and very
                       SPRD's permit jurisdiction                                                                                                                                          strong (VS) El Niho
                                                                                 0-                                                                                                        events that occurred
                                                                                                                                                                     89
                       (the beach zone line) prior to                               .I '1 68      70 I'l 1'@    7, 1.      ;7 1. 1. @. @1 @@ @3 @4 @6         @1        @O I               during the period.
                       1977, when DSL assumed                                                                                YEAR
                       joint permit authority (table
                       5). However, because of                                                F ANNUAL                      CUMULATIVE EKI EL NINO
                       overlapping jurisdiction
                       since 1977, 63% of the SPS
                       permits have been processed by both SPRD and                                          shore protection that might be substituted, the
                       DSL (table 5). Some of the duplication of effort                                      proposed design and how it relates to the severity
                       has been eliminated by ajoint application form                                        of the hazard or threat, and expected impacts. Al-
                       and ajointly signed permit, but more could be                                         though SPRD and DSL do conduct a limited as-
                       done.                                                                                 sessment of proposed SPSs, the lack of criteria or
                            Another finding related to the permit process is                                 structured process for assessing need, altema-
                       that there are no consistent criteria for when                                        fives, design, and impacts results in less than sat-
                         emergency" permits are warranted. The eligibil-                                     isfactory decisions and outcomes. Some
                       ity for emergency riprap of oceanfront lands that                                     examples illustrate this general point.
                       were not "developed" as of January 1, 1977 also                                       With regard to need and justification for a hard
                       needs to be determined (see table 2, objective 2).                                    SPS, there are no specific criteria to be applied to
                            Jurisdictional gaps and overlaps aside, the per-                                 make this determination (see table 2, objective 4).
                       mit process for SPSs has serious flaws, beginning                                     Absent such criteria, the permit record from the
                       with the permit application form itself. The form                                     Siletz cell indicates that in 35% of the cases, there
                       provides little of the information needed to make                                     was no hazard or actual threat that warranted is-
                       a thorough evaluation of the need and justifica-                                      suance of an SPS permit. Yet permits were is-
                       tion for the structure, the alternatives to hard                                      sued. In 28% of the cases examined, the lots for

                                                                                                                                                                                  153











                             GOVERNMENTAL                        TYPE OF PERMIT             TYPES OF SPSs                      AREA OF REGULATORY                  THRESHO
                             LEVEVAGENCY                                                    REGULATED                          JURISDICTION                        JURISDICT

                             Federal-Corps of                    NWP 13 w/regional          Riprap revetments; others if       Below ordinary high water           <500 ft in I
                             Engineers (COE)                     conditions                 notification procedures            (OHW)-rivers; or high tide          cu yd of ripi
                                                                 (new/repair)               followed and impact                line (HTL)-tidal areas              or HTL
                                                                                            minimal

                                                                 Regular (new/repair)       Vertical concrete and other        Same as above                       >500 ft in I
                                                                                            retaining walls, all                                                   >1/2 cu yd o
                                                                                            structures not covered by                                              OffW or In
                                                                                            NWP 13


                             State-Parks and                     Regular (new only)         All structural types,              West of the 1967 surveyed           None-all
                             Recreation Depart-                                             including sand or other fill       beach zone line (BZL)               covered, bu
                             ment (SPRD)                                                                                                                           required for
                                                                                                                                                                   original con

                                                                 Emergency (new             All structural types (usually      Same as above                       Same as abo
                                                                 only)                      riprap revetments)


                             State-Division of                   Regular (new/repair)       All structural types,              Line of established upland          >50 cu yd o
                             State Lands (DSL)                                              including sand or other fill       vegetation or highest               fill (sand, c
                                                                                                                               measured tide, whichever is
                                                                                                                               highest

                                                                 Emergency                  All structural types (usually      Same as above                       Same as abo
                                                                 (new/repair)               riprap revetments)


                             Local-city or county                Regular (may defer to      All types, but varies with         Varies, but may include             Varies
                                                                 SPRD/DSL process)          city/county                        areas landward of state
                                                                                                                               jurisdiction



                     Table 4. Jurisdictional comparison of shore protection regulatory programs in Oregon.






















                                                                                            TYPE OF PERNUT


                         SPSS           SPRD,          DSL regular     Joint          SPRD            DSL emerg.      Joint          NoSPRDI         Apparent/      Total SPSs
                         Built/time      regular       permit only     SPRD/DSL       emerg.          permit only     SPRD/DSL       and/or DSL      possible
                         period         permit only                    regular        permit only                     emerg.         jurisdiction    violation
                                                                       permit                                         permit


                         1967-76              53             na             na              13             na              na             46              1              113

                         1977-91              23             20             93               9              3               1             32             16              197

                         TOTAL                76             20             93              22              3               1             78             17              310
                         1967-91



                         1 SPS project is east of BZL (out of SPRD jurisdiction) or landward of upland vegetation line or highest measured tide (out of DSL jurisdiction)

                         SPRD-State Parks and Recreation Department
                         DSL-Division of State Lands
                         na-not applicable; DSL did not take permit jurisdiction over oceanfront SPSs until 1977.




                    Table 5. Regulated and unregulated SPSs constructed in the Siletz littoral cell, 1967-1991.







                                                                                                                                and expertise. Geotechnical
                                                                                                                                reports, sometimes prepared
                                                                                                                                to justify SPSs, generally do
                                              NUMBER OF SPSa
                                         360                                                                                    not give the rationale for the
                                         300                            . . ....                                 ......         proposed SPS in comparison
          Figure 4.                      250              .... ..      . ......                                                 with other alternatives con-
          Regulated and                  200                                                                      ........      sidered. Neither do they say
          unregulatedSPSs                                                                                                       why the specified design is
          constructed in the             150                                                                                    needed and rarely do they
          Siletz littoral cell,          100-                              ......                ..........     ....I....1
          1967-1991.                                                                                                            describe the impacts of the
                                          50-                                                                        ...        proposed structure. Also, the
                                             0                                                                                  lack of report standards and
                                                                    SPS REGULATORY STATUS                                       provisions for peer review
                                               E:SJ REGULAR PERMIT         EMERG. PERMIT =        VIOLATION                     lessens the usefulness of
                                               U11 NO JURISDICTION         TOTAL BPS$ BUILT                                     these documents.



                                  which SPS permits were issued were vacant,                             "AVERAGE"
                                  suggesting that the presence of upland improve-                        RIPRAP REVETMENT
                                                                                                         SILETZ CELL
                                  ments is not an important consideration in the                                                                   A, CK-1111,11
                                  project "need determination." In other cases                                          27ft
                                  where there was little hazard or threat, however,
                                  the state did take a hard line and denied permits.
                                  Yet the erratic record of permit denials over time                                                         16ft
                                  is further evidence of the lack of consistent deci-
                                  sion-making criteria-50% of all denials oc-
                                  curred in a single year and 83% in four years of
                                  the 25-year record.
                                      Similarly, there is no process for systemati-                      RIPRAP REVETMENT
                                                                                                         DESIGNED FOR MAXIMUM
                                  cally evaluating alternatives to hard SPSs (see                        RUNUP IN 100-YEAR STORM
                                  table 2, objective 5), even though Goal 17
                                  (Coastal Shorelands), and SPRD and DSL mgu-
                                  lations assert that such alternatives are "pre-                                        15ft
                                  ferred." What those alternatives are and                                                          _T
                                  situations where they might be applicable have                                                      loft
                                  not even been specified.
                                      As with other aspects of the process, the
                                  evaluation of potential impacts of SPS proposals
                                  is weak (see table 2, objective 6). SPRD does use
                                                                                                     Figure 5. The "average" riprap revelment sizefor the
                                  its beach improvement standards as an evaluafion                   Siletz cell (A) contrasted with a hypothetical structure sized
                                  guide; however, while this is helpful, it is rela-                 for maximum wave run-up (see Shih 1992) during a 100-
                                  tively superficial and limited by their authority                  year storm at extreme high tide at Gleneden Beach, Oregon
                                                                                                     (B).
                                  and expertise. SPS designs are not critically re-
                                  viewed and in most cases are many times larger                         Consideration of the long-term impacts of
                                  than needed (figures 5 and 6), resulting in unnec-                 SPSs, required by state policy, is simply not a
                                  essary public beach encroachment (table 6 and                      high priority for SPRD or DSL given the many
                                  figure 7). The physical impacts of structures am                   more immediate problems with the process and
                                  also not evaluated, for lack of both information                   the decisions that must be made (see table 2,


                                  156














                                                                                                    Figure 6. The
                                                                                                    Furman riprap
                                                                                                    revetment at S. 441h
                                                                                                    St. in Lincoln City
                                                                                                    is an e)areme case
                                                                                                    of an overdesigned
                                                                                                    structure.









                                                              Distance SPSs Extend West of the BZL (ft)                   Table 6. Shore
                                               0-10       11-20        21-30      31-40         >40      TOTAL            protection
                                                                                                                          structures built
                                                                                                                          west of the
                     Numbers of SPSs              61          53          33           9            1        157          beach zone line
                                                                                                                          (BZL), Siletz
                     SPS-occupied              0.76        1.75         1.30       0.90         0.47        5.17          littoral cell,
                     beach west of                                                                                        1967-1991.
                     BZL (acres)








                                                                  AREA IN ACRES
                                                              400--
                                                                                340 ac
                            Figure 7. Cumulative              350-                                           .. ..... ... . .....
                            loss of "dry sand                 300-
                            beach" area in the                250-
                            Siletz cell caused by
                            encroachment of shore             200-                                                        . ..... .
                            protection structures             150-                                          ........ ..     ... ............
                            west of the beach zone
                            line as compared to the           100-                             -86  ac       (1.5% of summer beach)
                            hypothetical summer                                                               (6.1@ ol.wInter beach)
                            and winter beach.                 50-
                                                                                                        9        5.17 ac

                                                                                      DRY SAND BEACH AREA -
                                                                     FM 200- SUM-ER       = 50' WINTER     =AREA LOST TO
                                                                                                                            SPS]

                                                           MHW TO BEACH ZONE LINE



                objective 7). Nevertheless, study results suggest               sand budget due to SPS installation (figures 8 and
                that long-term, cumulative impacts are potentially              9) may eventually lead to beaches that are nar-
                among the most serious concerns, especially in a                rower and less effective as erosion buffers. With
                littoral cell like the Siletz where cliff-supplied              the gradual loss of buffering beaches, episodic
                sand is an important contributor to the sand bud-               erosion will likely threaten more and more upland
                get. The gradual loss of cliff-supplied sand to the             development and result in an increasing rate of


                                                                                                                                       157







                                                                                                                                  management of coastal nahuw
                                                                                                                                  hazards.

                                                                                                                                  Policy Improvements Sug-
                                                                                                                                  gested by the Siletz Cell Study
        Figure 8. Sand can                                                                                                           A wide array of planning,
                                                                                                        77                        siting, and design decisions
        be supplied to the
        beach by the eroding                                                       A       *A
        cliff on the left; sand                                                                                                   made by individuals, busi
        supply has been cut
                                                                                                                                  nesses, local governments, and
        off by construction of
        a riprop revetment at                                                                                                     state and federal agencies are
        the base of the cliff                                                                                                     or should be-influenced by
        on the right.
                                                                                                                                  coastal natural hazards. Deci
                                                                                                                                  sions about how coastal lands
                                                                                                                                  should be zoned and used over
                                                                                                                                  t
                                                                                                                                       long term; decisions about
                                                                                                                                  he
                                                                                                                                  the layout of oceanfront subdi-
                                    SPS installation. The recreational values of the                      visions; decisions on the location, siting, and de-
                                    beach will be much diminished.                                        sign of private development; decisions to invest
                                                                                                          in, finance, and insure development; decisions to
                                                                                                          protect development, beaches, and recreational
                                    improving Coastal Natural Hazards                                     resources-all of these are affected by natural
                                    Policy in Oregon                                                      processes that present hazards to life and prop-
                                       Although there is a substantial base of public                     erty. Below I suggest policy and policy imple-
                                    policy for addressing many of the natural hazards                     mentation improvements that respond to the
                                    issues that arise in the siting and protection of                     decision-making shortcomings detailed earlier.
                                    oceanfront development, the above critique indi-                         Establish a simple, clear coastal hazard
                                    cates that improvements are needed in both the                        mitigation policy based first, on hazard avoid-
                                    substance and implementation of state and local                       ance; second, on minimizing the adverse ef-
                                    policy. Below I outline some preliminary mcom-                        fects of development in hazardous areas; and
                                    mendations, based on my findings in the Siletz                        finally, on compensation for unavoidable ad-
                                    cell case study. I also describe a new process Or-                    verse effects.
                                    egon is using to examine and improve its                                 In terms of an overall management strategy,
                                                                                                                                       hazard avoidance should be
                                                                                                                                       afundamental principle
                                                                                                                                       guiding the siting of new
                                              SAND VOLUME (1,000 CUBIC YARDS)                                                          oceanfront development
                                          20-                                                                                          along the Oregon coast.
                                                                                                                                       This should be the rule for
        Figure 9. Cumulative              15 -                                                                                         undeveloped raw land, for
        loss of sand supply                     39% OF ANNUAL SAND SUPPLY 'LOCKED UP'                                                  infill development, or for
        due to construction of             10-                                                                                         redevelopment or improve-
        shore protection
        structures in the                                                                                                              ment of existing upland
        Siletz littoral cell,              5- -                              -                                                         buildings or infrastructure.
        <1967-1991.                                                                                                                    If, as is often the case, de-
                                           0     <67     67-71 72-76 77-81 82-86                87-91 LOSS                             velopers cannot completely
                                                                           YEAR INTERVAL                                               avoid hazards, then they
                                              IMM00i                                           I I

                                               M Cum LATIVE LOSS                         NEW INTERVAL LOSS                             should-as much as pos-
                                               2Z POTENTIAL SUPPLY                                                                     sible-avoid the adverse
                                                                                                                                       impacts of hazard mitiga-
                                                                                                                                       tion, mainly by the use of

                                    158







                nonstructural alternatives to hard SPSs. Examples            management, and coastal planning should work
                include dune building along the oceanfront to cre-           together to develop special area management
                ate better buffers against episodic erosional                plans for discrete littoral cells. The "special area
                events, bank sloping and revegetation of sea                 planning" model is a well-developed and familiar
                cliffs, relocation of threatened upland structures,          one in Oregon, having been used to develop
                and the use of relatively small, dynamic protec-             coordinated plans for each of Oregon's 17
                tive structures. If for some reason hard SPSs can-           estuaries in the late 1970s and early 1980s (Davis
                not be avoided, compensation for unavoidable                 1980; Gusman and Huser 1984). The model is
                adverse impacts-individual and cumulative-                   also the foundation for the wetland conservation
                should be required. This hazard mitigation frame-            planning process the state legislature put in place
                work is similar to that which has been used for              in 1989 (ORS 196.678-196.681). Beachfront
                many years to avoid, minimize, and compensate                management plans for littoral cells, developed
                for the adverse impacts on wetland resources.                using the hazard mitigation framework suggested
                Such a framework could be implemented through                above, and based on hazard and sand supply
                the site assessment and setback procedures sug-              assessments and mapping, scenic resource
                gested next, as well as the beachfront planning              inventories, public recreation needs, and upland
                process outlined later.                                      development interests and plans, would resolve
                                                                             many of the shortcomings of present local plans.
                    Develop a more consistent, structured site               They would also facilitate more coordinated and
                assessment procedure and reporting process                   conscious decisions with respect to hazards.
                for development in hazardous areas, incorpo-                    Provide for more state oversight of local
                rating a coastivide construction setback proce-              land use decisions for coastal lands affected by
                dure. .                                                      hazards.
                    Two related tools for implementing the hazard               While local officials are unlikely to invite
                mitigation framewodc suggested above are (1) an              greater state oversight and access to land use de-
                improved site assessment and reporting process               cisions generally, having such oversight for these
                for areas subject to hazards and (2) a coastwide             few decisions (for example, the siting of ocean-
                building setback procedure. Standards and qual-              front development) would at least shift the politi-
                ity-assurance procedures, including third-party              cal burden of unpopular decisions to the
                peer review, need to be established for geological           somewhat more insulated state level. Although
                and geotechnical site assessment reports. These              this would not remove political and economic
                reports could be used to determine a hazard
                avoidance construction setback, using a consis-              influences ftom the oceanfront siting process, it
                tent statewide procedure, but applied on a site-by-          would provide a buffer for local officials and
                                                                             likely yield more consistent hazard avoidance de-
                site basis as a function of applicable ocean,                cisions. Again, analogies can be drawn with the
                beach, cliff, or other risk factors. Such a setback          wetland regulatory process, where development
                procedure would recognize the unique situation               conditions are largely determined through ille
                present at each location but provide overall con-            state and federal permit process. Many local gov-
                sistency of siting decisions with respect to ero-            emments have been more than willing to leave
                sion, flooding, landslide, and other hazards.                these decisions with the state because they lack
                    Prepare comprehensive, integrated                        the requisite expertise for assessment and because
                beachfront management plans for individual                   it distances them from decisions that are often
                littoral cells.                                              unpopular.
                    There is a critical need for a more coordinated             Consolidate SPRD and DSL beachfront
                beachfront development planning process for                  shore protection pern-dt programs into a single
                littoral cells along the coast, especially for               program at SPRD; elin-dnate gaps in jurisdic-
                shorelines with significant private ownership.               tion and enforcement authority.
                These private owners and the local and state                    The regulation of SPSs fits well with the over-
                officials charged with hazard assessment, beach              all beach management responsibilities of SPRD

                                                                                                                                       159







                            because of their historical emphasis and expertise      hazards, growing development pressures in haz-
                            in evaluating beachfront protection proposals for       ardous coastal areas, and weaknesses in present
                            recreational and access-related impacts and be-         hazard mitigation policies and their implementa-
                            cause they have a regular field presence. How-          tion--Oregon Sea Grant and the state coastal
                            ever, SPRD's jurisdiction over SPSs needs to be         management agency (DLCD) have organized a
                            extended to all beachfront structures that are          Coastal Natural Hazards Policy Working Group
                            likely to affect the resources and values protected     (PWG). The group is the centerpiece of Oregon's
                            by the Beach Law, not just those that extend west       coastal hazards policy improvement strategy, a
                            of the BZL. Sufficient Beach Law enforcement            program that addresses the federal Coastal Zone
                            authority, similar to that in the Removal/Fill Law,     Management Act amendments of 1990.
                            also needs to be established. DSL's present role           The PWG, which includes oceanfront land-
                            in beach management and regulation, which is            owners, real estate agents, local officials, a devel-
                            comparatively small, could be eliminated if the         oper, geologists, planners, biologists, and
                            above gaps were closed. Their program focus and         environmentalists, has taken up the task of identi-
                            expertise is clearly in the wetlands and waterways      fying important coastal natural hazard issues,
                            arena, not beaches. Wherever the beachfront per-        evaluating existing management strategies and
                            mit program is housed, responsibility for geologic      examining alternatives, and then recommending
                            and engineering review should be assigned to the        and supporting needed policy improvements to
                            state agency with the requisite expertise-the De-       decision makers at all governmental levels. The
                            partment of Geology and Mineral Industries              group will be meeting regularly over an 18-month
                            (DOGAMI).                                               period.
                               Clarify policies and improve the evaluation             The PWG is using a highly structured process
                            process for SPS permit applications, with em-           to develop their policy recommendations. The
                            phasis on determination of need and justifica-          entryway into the process is an "all-hazards/all-
                            tion, alternatives to hard SPSs, appropriate            decisions" matrix (figure 10) that is likened to a
                            design of SPSs, and impact assessment.                  large window with many panes. To organize the
                               A policy as to what constitutes "need and justi-     potential chaos associated with all hazards and all
                            fication" for a hard SPS is needed. For example,        types of decisions, the PWG confines itself to a
                                                                                    certain section of the matrix for each of its ses-
                            permit applicants should clearly demonstrate that       sions. For example, a PWG discussion session
                            a hazard exists and that upland improvements are        might confine itself to "locating private develop-
                            threatened. For officials to implement such po i-       ment in undeveloped areas as it relates to erosion
                            cies, standard hazard assessment procedures n d         and flooding hazards." Eventually, all of the ma-
                            to be developed and included in the permit re-          tiix "windows" get addressed.
                            view process.                                              The PWG process involves several stages. In
                               For situations where a bona fide hazard exists       stage I of the process (now underway), the PWG
                            and property is threatened, we need to establish        generates a list of problems within the selected
                            procedures to evaluate nonstructural alternatives       issue area, groups them by type, and ranks them
                            to hard SPSs. Alternatives that might be exam-          by relative importance. Using brainstorming, the
                            ined include landward relocation, dune building         group comes up with a set of alternatives and,
                            and stabilization, bank sloping and revegetation,       through guided discussion, relates them to the
                            selective beach nourishmenL and dynamic struc-          problems. In subsequent sessions, the PWG ex-
                            tures. Where hard SPSs are the only viable shore
                                                                                    amines issues and alternatives for each of the re-
                            protection solution, SPS design criteria vis-A-vis
                            the hazard and threat need to be established and        maining portions of the matrix. The product of
                            used.                                                   these sessions is a "working lise'of issues and
                                                                                    alternatives, organized around natural groupings
                            The Coastal Natural Hazards Policy Working              (education, assessment, planning, protection, and
                            Group                                                   so on).
                               In response to the problems detailed in this pa-        In stage 11 (about February 1993), the "work-
                            per-new scientific and technical information on         ing list" will be transformed into discrete sets of

                            160







                                       ALL-HAZARDS/ALL-DECISIONS MATRIX FOR CONSIDERATION
                                    OF COASTAL NATURAL HAZARDS POLICY ISSUES AND ALTERNATIVES


                                                         CHRONIC HAZARDS                                           CATASTROPHIC HAZARDS

              PRIVATE/PUBLIC                    Eros        Recess Slide           Flood      SLR         Gr-shak       Fault      Sub/F1 Liq/set         Slide       Tsun/Sei
              DECISIONS                                                                                                          10          1
              Locating private
              development in
              undeveloped areas
              Locating public
              infrastructure and facilities
              in undeveloped areas
              Designing private
              development in
              undeveloped areas
              Designing public
              infrastructure and facilities
              in undeveloped areas
              Protecting private
              development in
              undeveloped areas
              Protecting public
              infrastructure and facilities
              in undeveloped areas
              Locating private
              development in infill areas
              Locating public
              infrastructure and facilities
              in infUl areas
              Designing private
              development in infill areas
              Designing public
              infrastructure and facilities
              in infill areas
              Protecting private
              development in infill 7aras
              Protecting public                            7- 7- i
              infrastructure and facilities
              in infill areas
              Locating private
              development in developed
              areas
              Locating public
              infrastructure and facilities
              in developed areas
              Designing private
              development in developed
              areas--
              Designing public
              infrastructure and facilities
              in developed areas
              Protecting private
              development in developed
              areas
              Protecting public
              infrastructure and facilities
              in dtjtLoped areas


              RESPONSE PLANNING
              EMERGENCY


              POSTDISASTER
              LRECONSTRUCTION
              P@
                L

              Figure 10.


                                                                                                                                                        161







                           issues, alternative solutions or approaches, and a    Lands, and the Department of Geology and Min-
                           framework to evaluate their feasibility. At this      eral Industries.
                           point public workshops will be held and other
                           opinion-gathering efforts will be made. Then the      References
                           PWG will decide which alternatives should be
                           advocated for implementation. Finally, in stage       Davis, G.E. 1980. Special area management-
                           HI (fall 1993), policies and actions will be pack-       resolving conflicts in the coastal zone, Envi-
                           aged and recommended to local and state                  ronmental Comment No. 10:4-7.
                           policymakers.                                         DeGrove, J.M. 1984. Oregon: a blend of state and
                              In summary, the Oregon coast is affected by a         local initiatives. In Land, Growth and Politics,
                           variety of natural hazards-chronic erosion, land-        edited by J.M. DeGrove. Washington: Ameri-
                           slides, flooding, and potentially catastrophic           can Planning Association.
                           earthquakes and tsunamis. Hazard mitigation at        Good, J.W. 1992. Ocean shore protection policy
                           the state level is accomplished through state-man-       and practices in Oregon: an evaluation of
                           dated, locally implemented land use planning and         implementation success. Ph.D. diss., Depart-
                           development policy, and state regulatory pro-            ment of Geosciences, Oregon State University,
                           grams for shore protection. Hazards policy imple-        Corvallis.
                           mentation is generally ineffective, particularly      Good, J.W. and S.S. Ridlington, eds. 1992.
                           with respect to the cumulative effects of hard           Coastal Natural Hazards: Science, Engineer-
                           shore protection structures. Shortsighted land de-       ing, and Public Policy. Oregon Sea Grant,
                           velopment practices are, in part, driving the de-        Corvallis, Oregon.
                           mand for hard shore protection. Furthermore,          Gusman, S. and V. Huser. 1984. Mediation in the
                           present polices do not address the potential im-         estuary. Coastal Zone Management Journal
                           pacts of accelerated sea level rise expected next        11(4):273-295.
                           century or the very real thwat of a major subduc-     Komar, P.D. 1992. Ocean processes and hazards
                           tion zone earthquake and related hazards. To deal        along the Oregon coast. In Good and
                           with these implementation shortcomings and               Ridlington.
                           unaddressed hazards, Oregon Sea Grant and state       Komar, P.D. and S.M. Shih. 199 1. Sea cliff
                           coastal managers have organized a Coastal Natu-          erosion along the Oregon coast. In Coastal
                           ral Hazards Policy Working Group. The group              Sediments '91,1558-1570. Washington, D.C.:
                           represents a broad range of interests and is using       American Society of Civil Engineers.
                           an all-hazards approach to build consensus and        Kraus, N.C. and W.G. McDougal. 1992. Shore
                           develop recommendations for improved hazards             protection and engineering with special
                           mitigation policy.                                       reference to the Oregon coast. In Good and
                              This paper is the result of research sponsored        Ridlington.
                           in part by Oregon Sea Grant with funds from the       Madin, 1. 1992. Seismic hazards on the Oregon
                           National Oceanic and Atmospheric Administra-             coast. In Good and Ridlington.
                           tion, Office of Sea Grant, Department of Com-         Quinn, W.H., V.T. Neal, and S.E. Antunez de
                           merce, under grant no. NA89AA-D-SGIO8                    Mayolo. 1987. El Nifio, occurrences over the
                           (project no. R/CM-37-PD) and from appropria-             past four and a half centuries. J. Geophys.
                           tions made by the Oregon State Legislature. The          Rsch. 92(CI3):14,449-14,461.
                           work was also supported with funds from the Or-       RNKR Associates. 1978. Environmental hazard
                           egon Department of Land Conservation and De-             inventory: coastal Lincoln County, Oregon.
                           velopment through Section 306 of the Coastal          Shih, S.M. 1992. Sea cliff erosion on the Oregon
                           Zone Management Act, administered by NOAA,               coast: from neotectonics to wave runup. Ph.D.
                           Office of Ocean and Coastal Resources Manage-            diss., College of Oceanography, Oregon State
                           ment; and in part by funds from the State Parks          University, Corvallis.
                           and Recreation Department, the Division of State




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