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'@'@- - ,.--,,-" @ . .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. (IBM 177) z) N A :1 \n Tmn 'JIM C' oast Guard Station YAQUINA MAY STATE VA ,dX Y A 127 IN _a U IlUghto U IV 0 Q P." 0 .0ght Hinton F@t SouthWach 216 21 2 y Tm@ S A em A L,ght Tmn 14 1-17 2( I f + EDRT .9 19 7\ Is 12 XTf 0,. L YA Q UIN.4 @1 5t@ - \136 Holida\ B If 102 17 13everly Beach fill r BM Moloch Beach Rock Mr 0 Yaquina Head,', A $P20 kWU Figure 14. Environtnental Geology map of the Newport area, Lincoln County, Oregon. After Schlicker and others, 1973, -3 Ju-poff Joe- B- NEWPOR Pill 0 oast Guard E st.6 W a tttt Y A, 'Q u L,,hl, I R 4 L.ght g- inton 1@t Ut a@c Rock bbi -A A -V 21 '-N 2 Y a f P) 1,00 N!" L,ghl oo Lx -L. h Ill P R, 9 C@r 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 � 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- � 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 � 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 subsidence and flooding. The less dramatic, but 9:1-22. 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: the PNW coastal zone far more dynamic then Bulletin of the Association of Engineering previously assumed. Finally, increasing develop- Geologists 24:161-197. ment pressures on shoreline properties are certain Hebenstreit, G.T., 1988, Local tsunami hazard to yield increasing land-use conflicts between assessment for the Juan de Fuca plate area. people who want to build artificial structures and Unpublished Report for US Geological 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 Beach 54:3-12. ards resulting from earthquakes and extreme Komar, P.D., and S.M. Shih, 1991. Sea-cliff climatic conditions in the Cascadia margin. Fo- erosion along the Oregon coast. ASCE, cused research efforts are now needed to provide Coastal Sediments 91 Proceedings, pp. 1558- site-specific information for catastrophic hazard 1570. mitigation in the Pacific Northwest coastal zone. 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 MY 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 Balsille, J.H. and Berg, D.H. 1972. State of groin Hales, LZ 1981. Floating Breakwaters: State-of- design and effectiveness, Proceedings of l3di the-Art Literature Review, Technical Report Coastal Engineering Conference, American No. 8 1 - 1, Coastal Engineering Research Society of Civil Engineers, 1367-1383. Center, Vicksburg, Miss., 279 pp. Beach Erosion Board. 1954. Shore protection, Hanson, H. and Kraus, N.C. 1989. GENESIS: planning and design, Technical Report 4, U.S. Generalized Model for Simulating Shoreline Army Corps of Engineers, Washington, D.C. change, Report 1: Technical Reference, Clausner, J.E., Gebert, J.A., Rambo, A.T., and Tecbnical Report CERC-89-19, Coastal Watson, K.D. 1991. Sand bypassing at Indian Engineering Research Center, U.S. Army River Inlet, Delaware, Proceedings of Coastal Engineer Waterways Experiument Station, Sediments '9 1, American Society of Civil Vicksburg, Miss. Engineers, 1117-1191. Hanson, H. and Kraus, N.C. 1990. Shoreline Clemens, K.E. and Komar, P.D. 1988. Tracers of response to a single transmissive detached sand movement on the Oregon coast, Proceed- breakwater, Proceedings of 22nd Coastal ings of 2 1 st Coastal Engineering Conference, Engineering Conference, American Society of American Society of Civil Engineers, 1138- Civil Engineers, 2034-2046. 1351. Hanson, H. and Kraus, N.C. 1991 a. Numerical Corps of Engineers. 1972. The Role of Vegeta- simulation of shoreline change at Lorain, tion in Shoreline Management, 32 pp. Ohio, Journal of Waterway, Port, Coastal and Corps of Engineers. 1980. Low Cost Shore Ocean Engineering, 1170), 1-18. Protection-A Property Owners Guide, 159 Hanson, H. and Kraus, N.C. 1991b. Comparison PP. of shoreline change obtained with physical and Dally, W.R. and Pope, J. 1986. Detached break- numerical models, Proceedings of Coastal waters for shore protection, Technical Report Sediments '9 1, American Society of Civil CERC-86- 1, Coastal Engineering Research Engineers, 1785-1799. Center, U.S. Army Engineer Waterways Hanson, H., Kraus, N.C., and Nakashima, L.D. Experiment Station, Vicksburg, Miss. 1989. Shoreline change behind transmissive Dean, R.G. 1984. Principles of beach nourish- detached breakwaters, Proceedings of Coastal ment, in: P.D. Komar (Editor), Handbook of Zone '89, American Society of Civil Engi- Coastal Processes and Erosion, CRC Press, neers, 568-582. Inc., Boca Raton, Fla., 217-23 1. Hobson, R.D. 1977. Review of design elements Dean, R.G. 1986. Coastal armoring, effects, for beach-fill evaluation, Technical Paper No. principles and mitigation, Proceedings of 20th 77-6, U.S. Army Engineer Waterways Experi- Coastal Engineering Conference, American ment Station, Coastal Engineering Research Society of Civil Engineers, 1843-1857. Center, Vicksburg, Miss. Dean, R.G. 1991. Equilibrium beach profiles- Hotta, S., Kraus, N.C., and Horikawa, K 1987. characteristics and applications, Journal of Function of sand fences in controlling wind- Coastal Research, 7(l), 5 3 -84. blown wind, Proceedings of Coastal Sedi- ments '87, American Society of Civil Gravens, M.B. and Kraus, N.C. 1989. Represen- Engineers, 772-787. tation of groins in numerical models of Hotta, S., Kraus, N.C., and Horikawa, K. 1991. shoreline response, Proceedings of =H Functioning of multi-row sand fences in Congress, Hydraulics and the Environment, forming foredunes, Proceedings of Coastal International Association for Hydraulic Sediments '91, American Society of Civil Research, C515-C522. Engineers, 261-275. Griggs, G.B., Tait, J.F., Scott, K., and Plant, N. Jensen, R.E., Hubertz, J.M., and Payne, J.B. 1991. The interactions of seawalls and 1989. Pacific coast hindcast Phase 1111 North beaches: four years of field monitoring, Wave Information, WIS Report 17, Coastal Monterey Bay, California, Proceedings of Engineering Research Center, U.S. Army Coastal Sediments '9 1, American Society of Engineer Waterways Experiment Station, Civil Engineers, 1871-1885. Vicksburg, Miss. 98 Komar, P.D. 1986. El Nifto and erosion on the Kraus, N.C. (Editor), 1990. Shoreline change and coast of Oregon, Shore and Beach, 54, 3-12. storm-induced beach erosion modeling, a Komar, P.D. 1978. Wave conditions on the collection of seven papers, Miscellaneous Oregon coast during the winter of 1977-78 and Paper CERC-90-2, Coastal Engineering the resulting erosion of Nestucca Spit. Shore Research Center, U.S. Army Engineer Water- and Beach 46:3-8. ways Experiment Station, Vicksburg, Miss. Komar, P.D. 1991. Ocean processes and hazards Kraus, N.C. and Larson, M. 1988. Prediction of along the Oregon coast, present workshop initial profile adjustment of nourished beaches volume. to wave action, Proceedings of Beach Preser- Komar, P.D. and J.W. Good. 1989. Long-term vation Technology '88, Florida Shore and impacts of the 1982-83 El Nifto on the Oregon Beach Preservation Association, Inc., 125 -137. Coast, Proceedings of Coastal Zone '89, Kraus, N.C., Larson, M., and Kriebel, D.L. 199 1. American Society of Civil Engineers, 3785- Evaluation of beach erosion and accretion 3794. predictors, Proceedings of Coastal Sediments Komar, P.D., J.W. Good, and S.M. Shih. 1989. '9 1, American Society of Civil Engineers, Erosion of Netarts Spit, Oregon: continued 572-587. impacts of the 1982-83 El Nifio, Shore and Kraus, N.C. and Pilkey, O.H. 1988. (Editors). Beach, 57,11-19. The Effects of Seawalls on the Beach, Journal Komar, P.D. and McDougal, W.G. 1988. Coastal of Coastal Research, Special Iss .ue No. 4,146 erosion and engineering structures: the Oregon PP. experience, in: Kraus, N.C. and Pilkey, O.H. Larson, M., Hanson, H., and Kraus, N. C. 1987. (Editors), Journal of Coastal Research, Special Analytical solutions of the one-line model of Issue No. 4, The Effects of Seawalls on the shoreline change, Technical Report CERC-87- Beach, 77-92. 15, Coastal Engineering Research Center, U.S. Komar, P.D. and Rae, C.C. 1976. Erosion of Army Engineer Waterways Experiment Siletz Spit, Oregon, Shore and Beach, 44,9- Station, Vicksburg, Miss. 15. Larson, M. and Kraus, N.C. 1989a. Prediction of Komar, P.D. and S.M. Shih. 1991. Sea-cliff beach fill response to varying waves and water erosion along the Oregon coast, Proceedings level, Proceedings of Coastal Zone '89, of Coastal Sediments '91, American Society of American Society of Civil Engineers, 607-62 1. Civil Engineers, 155 8-1570. Larson, M. and Kraus, N.C. 1989b. SBEACH: Kraus, N.C. 1983. Applications of a shoreline Numerical model for simulating storm- prediction model, Proceedings of Coastal induced beach change, Report 1: empirical Structures '83, American Society of Civil foundation and model development, Technical Engineers, 632-645. Report CERC-89-9, Coastal Engineering Research Center, U.S. Army Engineer Water- Kraus, N.C. 1987. The effects of seawalls on the ways Experiment Station, Vicksburg, Miss. beach: a literature review, Proceedings of Larson, M. and Kraus, N.C. 1991. Mathematical Coastal Sediments '87, American Society of modeling of the fate of beach fill, in: H.D. Civil Engineers, 945-960. Niemayer, J. van Overeem, and J. van de Kraus, N.C. 1988. The effects of seawalls on the Graaff (Editors), Artificial Beach Nourish- beach: an extended literature review, in: Kraus, ments, Special Issue of Coastal Engineering, N.C. and Pilkey, O.H. (Editors), Journal of Vol. 16, pp. 83-114. Coastal Research, Special Issue No. 4, The McDougal, W.G., Sturtevant, M.A., and Komar, Effects of Seawalls on the Beach, 1-28. P.D. 1987. Laboratory and field investigation Kraus, N.C. 1989. Beach change modeling and of the impact of shoreline stabilization struc- the coastal planning process, Proceedings of tures on adjacent properties, Proceedings of Coastal Zone '89, American Society of Civil Coastal Sediments '87, American Society of Engineers, 553-567. Civil Engineers, 961-973. 99 McLellan, T.N. 1990. Nearshore mound con- Shore Protection Manual. 1984. (2nd ed.) 2 Vols., struction using dredged material, J. Coastal Coastal Engineering Research Center, U.S. Research, Special Issue No. 7, 99-107. Army Engineer Waterways Experiment McLellan, T.N. and Kraus, N.C. 199 1. Des' tation, U.S. Government Printing Office, ign S guidance for nearshore berm construction, Washington, D.C. Proceedings of Coastal Sediments '91, Ameri- Shows, E.W. 1978. Florida's coastal setback can Society of Civil Engineers, 2000-2011. line-an effort to regulate beachfront develop- Mohr, M.C. and Ippolito, M. 1991. Initial ment, Coastal Zone Management Journal, 4(1- shoreline response at the Presque Isle erosion 2),151-164. control project, Proceedings of Coastal Sunamura, T. 1984. Principles of sea cliff and Sediments '91, American Society of Civil platform erosion, in: P.D. Komar (Editor), Engineers, 1740-1754. Handbook of Coastal Processes and Erosion, Nakashima, L.D., Pope, J., Mossa, J. and Dean, CRC Press, Inc., Boca Raton, Fla., 233-265. J.L. 1987. Initial response of a segmented Walton, T.L. and Sensabaugh, W. 1978. Seawall breakwater system at Holly Beach, Proceed- Design on Sandy Beaches, University of ings of Coastal Sediments '87, American Florida Sea Grant Report, No. 29, 24 pp. Society of Civil Engineers, 1399-1414. Weggel, J.R. 1988. Seawalls: the need for Pope, J. and Dean, J.L. 1986. Development of research, dimensional considerations and a design criteria for segmented breakwaters, suggested classification, in: Kraus, N.C. and Proceedings of 20th Coastal Engineering Pilkey, O.H. (Editors), Journal of Coastal 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. � 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. 129 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. 130 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. 138 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 162 GAYLORDIN.. 2333 ISBN 1-88 1820-00-- fill 3 6668 14100 1034 .