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     LOW COST SHORE PROTECTION

                                        a Guide for Engineers and Contractors
                 TC
                 223
                 L6
                 1981

                            The U. S. Army Corps of Engineers
                            presents this     information as a
                            public service.     Inclusion of any
                            shore protection device or method
                            does not necessarily constitute a
                            government recommendation or en-
                            dorsement, nor is it guaranteed
                            that any particular method will be
                            successful for a specific applica-
                            tion.

               LOW COST SHORE PROTECTION
                                           a Gilide for Engineers and Contractor$

                                    US Department of Commerce
                                NOAA Coatital Services Center Library
                                     2234 South Hobson Avenue
                                     Charleston, SC 29405-2413

                                        TABLE OF CONTENTS

                                                                             Page

              INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . .     5

                   Low Cost Shore Protection . . . . . . . . . . . . . . .     5
                   The Shoreline Erosion Control Demonstration Program.    .   5
                   Shoreline Processes . . . . . . . . . . . . . . . . . .     6

              THE EROSION PROBLEM  . . . . . . . . . . . . . . . . . . . .    15

                   The Importance of Shoreform . . . . . . . . . . . . . .    15
                   The Causes of Erosion . . . . . . . . . . . . . . . . .    18

              A LOOK AT THE OPTIONS  . . . . . . . . . . . . . . . . . . .    21

                   No Action . . . . . . . . . . . . . . . . . . . . . . .    21
                   Relocation  . . . . . . . . . . . . . . . . . . . . . .    21
                   Bulkheads and Seawalls  . . . . . . . . . . . . . . . .    22
                   Revetments  . . . . . . . . . . . . . . . . . . . . . .    24
                   Breakwaters . . . . . . . . . . . . . . . . . . . . . .    25
                   Groins  . . . . . . . . . . . . . . . . . . . . . . . .    26
                   Beach Fills . . . . . . . . . . . . . . . . . . . . . .    28
                   Vegetation  . . . . . . . . . . . . . . . . . . . . . .    28
                   Infiltration and Drainage Controls   . . . . . . . . . .   29
                   Slope Flattening  . . . . . . . . . . . . . . . . . . .    29
                   Perched Beaches . . . . . . . . . . . . . . . . . . . .    29
                   Structures and Fills  . . . . . . . . . . . . . . . . .    31
                   Structures and Vegetation . . . . . . . ... . . . . . .    31

              THE DESIGN PROBLEM . . . . . . . . . . . . . . . . . . . . .    33

                   Functional Design . . . . . . . . . . . . . . . . . . .    33
                   Structural Design . . . . . . . . . . . . . . . . . . .    36

              SHORE PROTECTION METHODS . . . . . . . . . . . . . . . . . .    65

                   Bulkheads . . . . . . . . . . . . . . . . . . . . . . .    65
                   Revetments  . . . . . . . . . . . . . . . . . . . . . .    77
                   Breakwaters . . . . . . . . . . . . . . . . . . . . . .    96
                   Groins  . . . . . . . . . . . . . . . . . . . . . . . .   110
                   Beach Fills . . . . . . . . . . . . . . . . . . . . . .   118
                   Vegetation  . . . . . . . . . . . . . . . . . . . . . .   121
                   Perched Beaches . . . . . . . . . . . . . . . . . . . .   133

              PROPRIETARY DEVICES AND SPECIALTY  MATERIALS  . . . . . . . .  135

              OVERVIEW OF THE DESIGN PROBLEM . . . . . . . . . . . . . . .   139

                   Characterization of the Site   . . . . . . . . . . . . .  139
                   Water Levels  . . . . . . . . . . . . . . . . . . . . .   139
                   Wave Conditions . . . . . . . . . . . . . . . . . . . .   140
                   Selection of Devices  . . . . . . . . . . . . . . . . .   143

                                               3

                                        TABLE OF CONTENTS
                                            (Continued)

                                                                             Page

              PERMIT REQUIREMENTS   . . . . . . . . . . . . . . . . . . . .  145

              OTHER HELP . . . . . . .. . . . . . . . . . . . . . . . . . .  147

                    Corps of Engineers Offices  . . . . . . . . . . . . . .  147
                    State Coastal Zone Management Offices . . . . . . . . .  148
                    Other Sources of Information  . . . . . . . . . . . . .  153
                    Suggested Reading . . . . . . . . . . . . . . . . . . .  154

              GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . .   161

              LITERATURE CITED . . . . . . . . . . . . . . . . . .. . . . .  171

                                                4

              LOW COST SHORE PROTECTION

                                       a Guide for Engineers and Contractors

                                          INTRODUCTION

                   The purpose of this report is to familiarize engineers and
             contractors with various established methods of low cost shore
             protection. It is written for the individual who is knowledgeable
             in general civil engineering design and construction, but not a
             specialist in coastal engineering or shoreline protection.          This
             report can be used 'without other references, but many topics are
             discussed with only minimal detail, so some additional reading may
             be necessary to gain a better understanding of the text.             The
             Suggested Reading section at the end of the report lists a full
             range of readily available books, reports, and publications that
             are recommended for additional background study.

             LOW COST SHORE PROTECTION

                   In distinguishing between low cost and cheap, one should
             remember that practically any method of shore protection, if pro-
             perly implemented, is expensive.        significant investments are
             required to achieve the durability      needed to resist even small
             waves.   Low cost simply means that the various measures are com-
             mensurate with the value of individual residential or commercial
             properties. The total cost of implementation will vary with the
             different alternatives, but in all cases, there should be a suit-
             able (and affordable) range of solutions.

                   The methods described in this report are usually appropriate
             for use only in sheltered waters. That is, they are generally not
             intended for open coast sites where they would be exposed to the
             undiminished attack of large oceanic waves. Use of most of these
             structures in such areas is definitelV not recommended and entails
             a considerable risk of failure.

             THE SHORELINE EROSION CONTROL DEMONSTRATION PROGRAM

                   From 1975 to 1980, the U. S. Army Corps of Engineers conducted
             a program to develop and demonstrate low cost methods of shore
             protection.    This program was mandated by Section 54 of Public
             Law 93-251, the Shoreline Erosion Control Demonstration Act of
             1974. Working with the Soil Conservation Service, the Corps desig-
             nated 16 demonstration sites throughout the Atlantic, Gulf, and

                                                5

             Pacific coasts, Alaska and the Great Lakes.         These sites were
             chosen because they represented a broad cross section of shoreform.
             and environmental conditions.     This would permit wide application
             of the results obtained to other sites located throughout the
             country.   At each of these sites, various structures and kinds of
             vegetation were established to evaluate their effectiveness in the
             local environment.    Twenty-one additional supplemental sites were
             also chosen where existing shore protection devices had previously
             been established by others.

                  The devices at all 37 sites were intensively monitored over a
             period of months.    Data that were collected included daily visual
             observations of wave heights and directions, quarterly surveys of
             beach and offshore profiles, quarterly color aerial photos, quart-
             erly sediment sampling and gradation analyses, and monthly site
             visits with ground level photos.

             SHORELINE PROCESSES

                  Before developing a comprehensive solution for a client, it is
             first necessary to understand the coastal processes that are con-
             tributing to the erosion problem. The following sections present
             basic information about shoreline processes that will serve as a
             foundation for later discussions.     These sections are not exhaus-
             tive in their depth of coverage and cannot replace detailed and
             widely accepted texts such as the Shore Protection Manual [U.S.
             Army Corps of Engineers (1977c)].

             Wave Action

                  While waves are always present on the open coast, they are not
             continuous in sheltered waters.     Nonetheless., they are still the
             major cause of erosion in these areas. Several basic wave charac-
             teristics are important. The wave height is the vertical distance
             between the wave crest and trough, the period is the time (in
             seconds) it takes two successive wave crests to pass a stationary
             point, and the wavelength is the distance between successive crests
             (Figure 1).   Using linear wave theory (the simplest case), these
             characteristics are given by the expressions;

                                            L = CT                               (1)

             where L = wavelength in feet,
                   C = wave celerity (speed) in feet/second,
             and   T = wave period in seconds;
                                            C = 21 tanh   2Ttd                   (2)
                                                27E        L )
             where d = water depth in feet;                            2
             and   g = acceleration due to gravity, 32.2 feet/second

                                                6

                                           WAVELENGTH

                               WAVE
                               CREST

                                                  WAVE
                                                 HEIGHT
               STILLWATER

                LEVEL

                                                       WAVE TROUGH

                        WAVE PERIOD IS. THE TIME REQUIRED FOR SUCCESSIVE CRESTS TO
                        PASS A STATIONARY POINT.

                            Figure 1        Characteristics of Waves
                                                   2       (_In d )
             and                              L =-q-T tanh   L                      (3)
                                                 2n

                  As a wave moves through deep water       (depths greater than one-
             half the wavelength), the celerity and        wavelength remain essen-
             tially constant, because for d/L > 0.5 (deep water); the expression
             tanh [2nd/L] approaches unity. Therefore, since the period remains
             constant, the celerity and wavelength also do not vary. However,
             when a wave approaches the shallower water near the shore (where
             d/L <0.5), Equations (2) and (3) cannot be simplified by ignoring
             tanh [2nd/L].     From Equation (2), the celerity decreases with
             depth; the wave slows as it enters shallower water. The same is
             true with the wavelength, L, as can be seen from Equation (3),
             where it appears on both sides of the equation and an iterative
             solution is required.

                  As the wave continues to move in shoaling water, its profile
             begins to steepen and its gently rolling shape changes to a series
             of sharp crests with intervening flat troughs. At some point, this
             process can continue no longer and the wave breaks at the shore.
             The break point is a function of the wave height, period, water
             depth and bottom slope, but as a first approximation, assume that
             the wave breaks when the height is about 0.78 times the depth. For
             example, a 5-foot high wave breaks in a water depth of about 6.4
             feet.
                IILLWATE@R
                                  \@@@WA

                                                 7

                    Important wave properties are demonstrated when a train
              (series) of regular waves meets a solid barrier such as an offshore
              breakwater (Figure 2). Wave diffraction occurs when the waves pass
              the breakwater and wave energy is transferred along their crests to
              the quiet area in the   shadow of the   structure. This   causes waves
              to form in the shadow    zone  that are smaller than in   the adjacent
              unprotected zone.

                                                DIFFRACTION
                                                  ZONE \
                                                Small Waves)

                                          BREAKWATER

                 UNPROTECTED
                     ZONE
                 (Large Waves)

                                               REFLECTION
                                                  ZONE
                                              Crossing Waves)

                      Figure 2         wave Diffraction and Reflection

                   Wave reflection occurs on the offshore side of the breakwater.
              While waves passing the structure are diffracted, the portions
              striking the breakwater are reflected like a billiard ball from a
              cushion.   If the structure is a smooth vertical wall, the reflec-
              tion is nearly perfect; and if the wave crests are parallel with
              the breakwater, the reflected and incident waves will reinforce
              each other to form standing waves twice as high as the incident
              waves.  This could cause considerable bottom scour at the toe of,
              and offshore from, the structure.      I f the waves approach at an
              angle, no standing waves will form, but the resulting water sur-
              face, with crossing wave crests, will be rough, and choppy. These
              short-crested waves could also cause, considerable bottom scour.

                   The final important wave characteristic is evident when waves

                                                8

             break either on a beach or structure -       The uprush of water after
             breaking is called runup and it expends the wave I s remaining en-
             ergy.   The runup height depends on the roughness and steepness of
             the structure or beach and the characteristics of the wave.             In
             general, increased roughness reduces runup.

             ,Sediment Transport

                   The large variety of littoral (shoreline) materials include
             rock, boulders, cobbles, gravels, sand, silt, and clay. A number
             of classification systems have been developed to identify the'se
             materials, and typical scales of sizes are given in Figure 3.

                   Rock characterizes cliff shorelines, such as along the coasts
             of northern California. Boulders are often present at the base of
             such cliffs because of rock fracturing and weathering. Cobbles and
             gravels are prevalent beach materials in the Pacific Northwest,
             Alaska, and the Great Lakes area. Sand, the most common shoreline
             material, is found in virtually all coastal areas. -Silts and clays
             generally occur on bluff shorelines or marshes, such as along the
             Great Lakes and various bays.

                   Littoral materials are derived from the deterioration and
             erosion of coastal bluffs and cliffs; the weathering of rock mater-
             ials found inland and transported to the shore by rivers and
             streams; the disintegration of shells, coral or algae to form
             carbonate materials; and the production of organic material (gen-
             erally peat) by coastal marshes and wetlands.

                   Failure or erosion of a bluff causes material to be deposited
             at the base. Waves sort this material and carry the fine-grained
             silts and clays offshore where they settle to the bottom.              The
             original deposit is eventually reduced to sand and gravel fractions
             which form a beach. Eventually, if no other littoral material is
             carried to the site by waves, even the sand and fine gravel will
             disappear down the coast or offshore, leaving only coarse gravels
             behind. However, a new supply of material may be deposited on the
             beach by a fresh failure of the bluff, and the process begins
             again. In many cases, therefore, the littoral materials comprising
             beaches are often derived from erosion of the shoreline itself.

                   Rivers and streams that carry sediments eroded from the inland
             land mass are a second source of littoral material, particularly
             during floods. Material from this source is predominantly smaller
             than sand, particularly for large rivers.        These silts and clays
             are largely deposited far offshore.          Smaller rivers that flow
             through sandy drainage areas may carry significant quantities of
             sand during floods.     However, the total contribution of sand by
             rivers and streams is probably considerably less than from erosion
             of the shores themselves.

                   Coral reefs, shells, and other plant or animal matter are a
             third material source.       They gradually break and weather into

                                                 9

                             American Society for               Colloids           Clay                    Silt                     Fine               Coarse                              Gravel
                              Testing Materials                                                                                     Sand                Sand

                             American Association of           Colloids             Clay                   Silt                     Fine              Coarse            Fine        medium      Coarse          Boulders
                             State Highway Officials                                                                                Sand                Sand           Gravel       Gravel      Gravel

                                                                                                    Silt                  very     Fine                     Ve
                             U.S. Department of                      Clay                                                 Fine                              Coarse    Fine Gravel        Coarse Gravel          Cobbles
                               Agriculture                                                                                Sand     Sand                     Sand

                             Civil Aeronautics                             Clay                           Silt              Fine Sand           Coarse Sand                                 Gravel
                             Administration

                             Unified Soil Classification
                             (Corps of Engineers,                            Fines (Silt or Clay)                                Fine Sand            Medium       Coarse        Fine          Coarse           Cobbles
                             Department of the Army,                          Distinction  Based On Plasticity                                         Sand         Sand        Gravel         Gravel
                             and Bureau or Reclamation)

                                                                                        0     co 0
                                                           WIM                                                                                                                                                      T

                                                                                                                                          0    0
                                                           U.S. Standard Sieve Sizes                                                                                                      I   I                 I

                                                           Phi Scale

                                                                          Figure 3                         Common         Soil       Classification Systems
                                                                                                          [After          Winterkorn and Fang (1975)]

              carbonate sands which are, for instance, the primary components of
              beaches south of Palm Beach, Florida. Swamps, marshes, and coastal
              wetlands produce peats and other organic matter, also a source of
              littoral material.    Too light to remain in place under continued
              wave action, they are ultimately washed offshore unless stabilized.

                   Littoral materials are transported along the shore by wave
              action. Approaching from deeper water, the shoreward portion of a
              wave moves in progressively more shallow water than the section
              farther of fshore.  This portion begins to slow, which causes the
              wave to bend (refract) until breaking at an angle to the beach.
              This creates considerable turbulence that temporarily suspends the
              bottom sediments and carries them up the foreshore (beach face) in
              the general direction of wave advance.       The motion stops a short
              distance up the beach, and then reverses direction back down the
              slope.  However, the downrush does not retrace the same path, but
              rather, moves directly down the foreshore in response to gravity.
              The next wave repeats the process, moving the material downdrift
              along the beach.

                   Littoral transport occurs not only by rolling bedload, as
              above, but also by the movement of suspended sediment. The waves
              generate a longshore current that flows through the area where they
              break (breaker zone).     Alone, it is generally too weak to move
              appreciable quantities of sediment; however, the turbulence from
              breaking waves suspends sediments that can then be moved downdrift
              by the longshore current.       This sediment generally settles out
              within a short distance, but the next wave provides additional
              movement. Therefore, longshore transport is caused by the zig-zag
              movement of bedload up and down the beach, and the turbulence and
              action of the wave-induced longshore current.

              Water Level Variations

                   The water surface elevation itself constantly changes with
              time.   The stillwater level, or the water level with no waves
              present, changes because of three processes; astronomical tides,
              storms, and periodic lake level variations.

                   Astronomical Tides. Tides are generated by the gravitational
              attraction between the-earth, moon, and sun, and are classified as
              diurnal, semidiurnal, or mixed. Diurnal tides have only one high
              and one low each lunar day.      Semidiurnal tides have two approxi-
              mately equal highs and two approximately equal lows daily. Mixed
              tides are intermediate between them and typically have two highs
              and lows that occur each day. However, in contrast to semidiurnal
              tides, there is a large inequality, or difference in height, be-
              tween either successive high or successive low waters. (Figure 4).
              Most Atlantic coast tides are semidiurnal and the heights of suc-
              cessive highs or lows are approximately equal.        Gulf and Pacific
              coast tides tend to be mixed, and in most cases, there is a dis-
              tinct inequality between successive highs or lows.

                                                11

                                  0        6         12        18         0         6      12         18        0         6        12 hours
                        - 12 ft.                                          I   -     I      I
                        -10                                    -Tidal     Day
                        -8                                                Tidal Period

                           6

                        -4

                        -2
                        -0-Datum
                        --2

                        --4 ft.

                                                                       SEMIDIURNAL

                                 0         6         12        18         0         6      12         18        0         6        12 hours
                        -12 ft.                                                 Flo Iad Tide            bb Tide
                        -10            High Tide,,,
                        -8

                        -6

                        -4

                                  1                                                                                      @40
                        - O-Daturn
                        --2
                        --4 ft.                                                     Tide

                                                                          DIURNAL

                                 0         6         12        18         0         6      12         18        0         6        12 hours
                        -12  f t.                                                         Tidal Day                       igher High WateF
                        -10                                                                 1 [-Tidal     Period
                        -8                                                               Lo er Hi     Water
                        -6                                Tidal Rise
                        -4

                        -2
                        -0-Dotum
                        --2                                                             Tidal Range           Higher Low Water
                                                         Lower Low Water
                             f t.                              I      ---1-                 1         1         1         1    ,   1.      1
                                                                             MIXED
                                                       Figure 4                     Types of Tides
                                                                                                      1
                                                                                    Wiegel                53)]
                                                               rN

                                                                                                                          H
                                                                                                         Pe,,od-,

                                                                                                           r
                                                                                                      Aote

                                                                                    12

                  In addition, the tidal range, or difference in elevation
             between the high and low waters, tends to fluctuate throughout the
             month.   These tidal range variations are caused by changes in the
             distance between the earth and moon (perigean and apogean tides),
             the declination of the moon (equatorial and tropical tides), the
             declination of the sun, and the phase of the moon (spring or neap
             tides).   (See GlossarV.)     The tides are highest during spring,
             perigean and tropical tides and are particularly high when these
             are approximately in phase.
                  Tides are also present on the Great Lakes, but they are small
             and not significant for practical problems of shore protection
             design.
                  Some key tidal datums, shown on Figure 5, are important be-
             cause of their wide use. Not shown are datums for the Great Lakes,
             where all levels are ultimately referenced to the International
             Great Lakes Datum (see GlossarV). Each lake has a designated chart
             datum [Low Water Datum   (LWD)] based on the IGLD.

                 MHHW    A  A   A    A                             A   A
                  MHW It 11 It 11 11   It R A                   It I
                  MSL  A   A      A
                  MTL
                 MLW                     11 If V_                V
                MLLW          V           V V

                                     5             9             13
                                               D A Y S

                        Figure 5          Illustration of Tidal Datums
                                             [After Harris (1981)]

                  Storm Ef fects.    The passage of storms tends to increase the
             stillwater level through two principal mechanisms:             atmospheric
             pressure effects, and stress caused by storm winds blowing across
             the water.   Atmospheric pressure differences across a large water
             body cause a rise in the water level in the lower pressure area
             (inverse barometer effect). Water surface rises of one or two feet
             are common in niany areas under this effect.

                  Enclosed water bodies (such as the Great Lakes) can also
             respond to storm forces by seiching. This       occurs when storm winds
             or pressure effects drive the water surface higher at the downwind
             end of a lake. The passage of the storm front releases this water,
             and causes a periodic oscillation within the basin that will con-
             tinue for several cycles.       On the Great Lakes, seiching is most
             pronounced on Erie, because its long axis more closely matches
             predominant storm tracks and its relatively shallow depths lead to
             higher storm setup levels.

                                                13

                   Wind stress also tends to drive the water on shore to above
              normal heights (storm setup). This continues until the tendency
              for the water to flow back to its normal level balances the forces
              driving it on shore.   The high winds associated with storms also
              generate large waves, with their effects being felt in addition to
              the elevated storm surge levels.

                   Lake Level Variations.   Water levels in the Great Lakes are
              also subject to periodi-C changes.   Records of lake levels dating
              from 1836 reveal seasonal and annual changes which are due to
              variations in precipitation annually, and from year to year. Lake
              levels (particularly Ontario and Superior) are also partially con-
              trolled by regulatory works operated jointly by Canadian and U. S.
              authorities, and these may result in minimizing lake level changes.
              Average monthly lake level elevations showing data for the past
              calendar year and present year-to date, and a forecast for the next
              six months, are published monthly by the U. S. Army Corps of Engi-
              neers, Detroit District (see Other Help Section).

                                               14

                                      THE EROSION PROBLEM

              THE IMPORTANCE OF SHOREFORM

                   The land-sea boundary in characterized by many shapes and con-
              figurations.   Geologists have devised elaborate classification
              systems to describe these various features.      For the purposes of
              understanding basic shoreline processes and for designing appro-
              priate corrective measures, however, it will only be necessary to
              informally classify shorelines as either bluffs, low erodible
              plains (including sandy beaches), or wetlands. Many shorelines, of
              course, contain two or even all three of these basic features.

              Bluff Shorelines

                   A distinction will be drawn between bluffs and cliffs. Cliffs
              will be defined as shorelines composed of relatively sound rock.
              These rarely undergo severe or sudden erosion problems, but may
              experience slow, steady retreat over a long period of years. Such
              shorelines generally cannot be treated with low cost solutions
              because available alternatives are usually less durable than the
              cliff rock itself.

                   On the other hand, bluffs are composed of sediments such as
              clay, sand, gravel, or erodible rock and erosion problems are often
              present along these kinds of shorelines. The most prevalent causes
              of bluff erosion are toe scour by wave action, surface runoff, and
              drainage and infiltration problems that lead to slope stability
              failures.

                   An important factor to consider is whether a bluff is high or
              low.  While no precise definition is possible, many writers have
              described high bluffs as those being greater than 20 or 30 feet
              high or, using a different criterion, a low bluff might be clas-
              sified as one that can stand alone, while a high bluff must either
              be protected, or otherwise treated, to remain standing.

                   In evaluating conditions at a site, it is necessary to deter-
              mine which of the above processes is primarily responsible for the
              erosion problem. Slope stability problems that are not aggravated
              by toe undercutting should be treated using established civil
              engineering techniques of slope stability analysis and design.
              Typical solutions could include vertical or horizontal drains,
              slope regrading and terracing, surface drainage controls, elimi-
              nation of unnecessary surcharges at the top of the slope, and
              buttressing the toe.

                . Wave action at the toe which undermines the bluf f can be
              treated using a low cost shore protection device.      Important fac-
              tors in selecting a device will include the relative steepness of
              the offshore bottom slope, and whether a sand beach is present at
              the base of the bluff. These are often derived from bluff materi-
              als that have fallen from above, and they provide a buffer against

                                               15

              normal wave action and may serve as a suitable foundation for
              various protective devices. During severe wave activity, however,
              waves can reach the bluff itself and erode or undercut the toe.
              Depending on the strength and characteristics of the bluff materi-
              als, this may cause the bluff to fail in a relatively short time.

                   The slope of the offshore bottom is also important.       I f the
              offshore slopes are steep, deep water is closer to shore, larger
              waves can reach the bluff, and maintenance of a protective beach is
              more difficult.    Conversely, flat offshore slopes inhibit heavy
              wave action at the bluff and provide for potentially better protec-
              tive beaches.

              Low Erodible Plains and Sand Beaches

                   These are the most common shoreforms throughout most areas of
              the United States. They are primarily composed of sands and grav-
              els that gently rise from the water's edge and seldom attain a
              height of more than five to ten feet above the stillwater level.

                   Figure 6 is a definition sketch of an ideal  ized beach profile.
              Waves approach from offshore, finally breaking and surging up the
              foreshore. Above the foreshore, the profile flattens considerably
              to form a broad berm which is not reached by normal wave activity.
              The beach berm will sometimes be backed by a low scarp leading to a
              second berm and eventually to a bluff or sand dune.

                   The profile will reach some equilibrium shape in response to
              normal water levels and wave activity. This equilibrium will be
              disturbed   and erosion will begin if the long-term water level
              rises  or predominant wave heights increase.      For a water level
                                                  - NEARSHORE(littoral) ZONE
                      UPLANDW-       BEACH          (extends through breaker zone)
                                 BACKSHORE  __F70RE-                       OFFSHORE
                                             SHORE

               BLUFF or
                                      RM
               ESCARPMENT
                                                SURGE
               BEACH SCARP                                    BREAKERS

               HIGH WATER LEVEL
               LOW WATER LEVEL
                       CREST OF BERM----/

                                           PLUNGE POINT

                                                                      BOTTOM

                           Figure 6        An Idealized Beach Profile
                         [After U.S. Army Corps of Engineers (1977c))

                                                1.6

             rise, a new equilibrium profile will eventually form with the same
             shape as the old, but shifted landward and upward.           Similarly,
             increased wave activity causes a nearshore bar to grow as the beach
             erodes.  Eventually, as this bar grows and the depths of water
             decrease, the larger waves will break farther offshore.            This
             weakens their attacks on the beach and equilibrium is restored.

                  At open coast sites, the return to normal water levels and
             waves will initiate a healing process that may return the profile
             to essentially its initial position.       This is because the flat
             swells tend to move sand back to the beach from the nearshore bar.
             At sheltered sites, however, these swells are not present, so the
             healing process  never occurs, and storm-caused erosion losses tend
             to be permanent.

                  Changes in  the sediment supply from updrift will also cause
             movement of the  profile. A decrease in the supply will cause the
             beach to erode,  and the profile will retreat landward, while still
             maintaining the  same shape. Conversely, an increase in the supply
             will cause accretion and the profile will advance toward the water.

             Wetlands and Marshes

                  Although they are treated separately in this section, wetlands
             and marshes usually occur in combination with sand beaches or low
             erodible plains.    For federal regulatory purposes, wetlands are
             defined as:

                       "Those areas that are inundated or saturated by surface
                  or groundwater at a frequency and duration sufficient to
                  support, and under normal circumstances do support, a pre-
                  valence of vegetation typically adapted to life in saturated
                  soil conditions. Wetlands generally include swamps, marshes,
                  bogs, and similar areas."       [U. S. Army Corps of Engineers
                  (1977b)]

                  Marsh plants are primarily herbaceous (lack woody stems) and
             include grasses, sedges and rushes. The species present depend on
             location and whether the marsh is low (regularly flooded) or high
             (irregularly flooded).

                  Until recently, marshes were considered undesirable and regu-
             larly drained and filled for new development or agriculture. Their
             value has now been recognized as an important environmental re-
             source, but they also protect the shore by absorbing the energy of
             approaching waves and trapping sediment that is being carried along
             by currents.    These shore protection qualities     are particularly
             important when the marsh fronts a sandy beach or other area where
             erosion is to be prevented.      In that case, the   marsh provides a
             front line of defense for the shore. While it may not provide full
             protection, it may, at least, partially dampen wave action and
             allow for less massive and costly backup protection.

                                               17

               THE CAUSES OF EROSION

               Wave Action

                    Wave action is the most obvious cause of shoreline erosion.

               Littoral Material Supply

                    Stable shorelines    are in a state of dynamic equilibrium.
               Waves keep the littoral   materials in constant motion in the down-
               drift direction, and the  shoreline remains stable provided there is
               an equal supply of material from updrift. When the updrift supply
               is deficient, the shoreline erodes.

                    A substantial portion of the littoral material supplied to
               shorelines is the result of updrift erosion.       If large amounts of
               the updrift shoreline are suddenly protected, material is lost to
               the littoral system.    This decreases the supply to the downdrift
               shore, resulting in erosion problems unless that land is also
               protected.

                    Determining the longshore transport direction is sometimes
               necessary. This is usually a difficult task because it depends on
               wave directions that can vary considerably with the seasons.
               Summer winds (and waves) may be from one predominant direction,
               while winter storm winds may be from an entirely different quad-
               rant.  When the winds and waves change direction, the transport
               direction also changes (transport reversal).

                    The gross longshore transport rate is the quantity of sand
               (usually in cubic yards per year) that moves past a fixed point in
               either direction. The net longshore transport rate is the quantity
               that moves in the predominant direction minus the quantity that
               moves the other way. The net transport rate is specified by both
               quantity -and direction (e.g., 10,000 cubic yards per year to the
               east).

                    Transport rates are important when considering accretion
               .devices such as breakwaters and groins because it is necessary to
               judge the effects of device construction on the littoral system,
               particularly with respect to potential downdrift damages. A pre-
               cise estimate will not usually be possible, but it may be feasible
               to examine similar structures or harbor works that have been con-
               structed in the past for evidence of accretion over known periods
               of time.    If nothing else, this should reveal the predominant
               transport direction and a crude measure of the possible transport
               rate.  This should be an acceptable level of precision for small
               scale, low cost devices.

               Slope Stability

                    Slope stability analysis is covered in standard geotechnical
               engineering textbooks [e.g., Lambe and Whitman (1969) and Winter-

                                                 18

           korn and Fang (1975)]. Major stability problems are most likely at
           high bluff shorelines where the heights are 20 feet or more.
           Except where toe protection is needed, slope stability problems on
           high bluffs tend to be beyond the range of low cost solutions.

                                           19

                                     A LOOK AT THE OPTIONS

                   Three basic choices are possible in response to an erosion
             problem: no action, relocation of endangered structures, and posi-
             tive corrective measures.     The latter includes devices that di-
             rectly armor the shore, those that intercept and dissipate wave
             energy, and those that retain the earth slopes against sliding.
             Each alternative requires an evaluation of the planned land uses,
             money and time available, and other effects that may result from
             the decision.

             NO ACTION

                   This is a decision-aid that can be used to evaluate different
             alternatives.   Because even low cost solutions can require sub-
             stantial investments, it is preferable to closely estimate poten-
             tial losses using this alternative, particularly if no dwellings
             are directly threatened, and only undeveloped land or inexpensive
             structures are in danger.     Also, erosion problems are sometimes
             caused by temporary factors (e.g., unusually high Great Lakes
             levels) that may abate. The resulting erosion, therefore, may slow
             before any action is taken.      This could eliminate the immediate
             need for protective devices, or it could mean choosing a smaller
             scale, less expensive, device.

             RELOCATION

                   In most cases, some action is necessary.        It may be less
             expensive to relocate endangered structures than to invest in shore
             protection. Relocation can be to an entirely different site or it
             can be a setback farther from the water at the present site. The
             required setback must be carefully evaluated because the consid-
             erable expense of moving a building could be wasted if the setback
             is insufficient.

                   The first step is to evaluate the long-term erosion rate.
             This  is difficult because reliable historical data on past shore-
             line  positions is often lacking. Possible sources of data include
             a time sequence of aerial photographs or shoreline maps.        If the
             property owner has occupied the site for many years (say 25 or
             more), and has observed slow shoreline retreat during that time,
             the annual erosion rate could be approximated by dividing the total
             amount of retreat by the number of years of observation.            For
             instance, if the shoreline steadily receded     300 feet in 30 years,
             the estimated average erosion rate is about     10 feet/year. A set-
             back of 100 feet could produce an additional   10 years of life for a
             structure, provided erosion continues at the   same rate.

                   Conversely, if the shoreline was stable   for years and suddenly
             retreated 300 feet in only 5 years, relocation on the same site may
             be risky and not generally advisable unless considerable setback
             room is available.

                                               21

              BULKHEADS AND SEAWALLS

                   The terms bulkhead and seawall are often used interchangeably.
              In a strict sense, however, bulkheads are retaining walls whose
              primary purpose is to hold or prevent sliding of the soil while
              providing protection from light-to-moderate wave action. Seawalls,
              on the other hand, are structures whose primary purpose is to
              protect the backshore from heavy wave action. Their massive size
              generally places them beyond the low cost range. Also, they are
              not generally needed in sheltered waters where large waves are not
              generated (except perhaps in the Great Lakes).

                   Bulkheads can be used to protect eroding bluffs by retaining
              soil at the toe, thereby increasing stability, or by protecting the
              toe from erosion and undercutting. They are also used for reclama-
              tion where a fill is needed in advance of the existing shore.
              Finally, bulkheads are used for marina and.other structures, where
              deep water is needed directly at the shore .(Figure 7).

                   Construction of a bulkhead does not insure stability of a
              bluff.   If a bulkhead is placed at the toe of a high bluff steep-
              ened by erosion to the point of incipient failure, the bluff above
              the bulkhead may slide, burying or moving the structure toward the
              water. To increase the chances of success, the bulkhead should be
              placed lakeward of the bluff toe, and if possible, the bluff should
              be graded to a flatter, more stable slope.

                   Bulkheads protect only the land immediately behind them and
              offer no protection to adjacent    areas up- or downcoast, or to the
              fronting beach.   In fact, their  vertical faces reflect wave energy
              which may cause increased scour and could lead to a loss of any
              existing fronting beach.    If the downdrift beaches were previously
              supplied by erosion of the land    now protected, they may erode even
              more quickly.   If a beach is to   be maintained adjacent to a bulk-
              head, additional structures such   groins or detached breakwaters may
              be required.

                   Bulkheads may be either cantilevers or anchored (like sheet
              piling), or gravity structures (like sand-filled bags). Cantilever
              bulkheads require adequate embedment to retain soil, and are used
              where low heights are sufficient. Toe scour reduces their effec-
              tive embedment and can cause failure.         Anchored bulkheads are
              usually used where higher structures are needed. They also require
              adequate embedment (although less than cantilever bulkheads) to
              function properly, but they tend to be less susceptible to toe
              scour.

                   Gravity structures eliminate the need for heavy pile driving
              equipment and are often appropriate where subsurface conditions
              hinder pile penetration. However, they require strong foundation
              soils to adequately support their weight, and they normally do not
              sufficiently penetrate the ground to develop reliable soil resis-
              tance on the offshore side.     Therefore, they depend primarily on
              shearing resistance along the base of the bulkhead to support the

                                                22

                                                    RETAIN BLUFF

                  LAND  RECLAMATION                   DOCKING STRUCTURE

                             Figure 7       Uses of Bulkheads

            applied loads.   Gravity bulkheads also cannot prevent rotational
            slides in materials where the failure surface passes beneath the
            structure.  Their use, therefore, is generally limited to rela-
            tively low heights where their cost is comparable to cantilever
            sheet pile bulkheads.

                                            23

              REVETMENTS

                   A revetment is placed on a slope to protect it and adjacent
              uplands against scour (Figure 8).      It depends on the underlying
              soil for support, so it must be built on a stable slope. An un-
              stable bank must first be properly graded before construction.
              Fill material, when needed to achieve a uniform grade, must be
              adequately compacted.

               OVERTOPPING
                    APRON

                                                  ARMOR LAYER

                                                                              M H W

                                                                TOE
                                                                              MLW
                                                             PROTECTION
                   GRADED STONE
                       FILTER

                           Figure 8         Typical Revetment  Section

                   Revetments protect only the land immediately behind them and
              provide no protection to adjacent areas. Erosion may continue on
              adjacent shores, and near the revetment may be accelerated by wave
              reflection from the structure, although not as seriously as with
              vertical-faced bulkheads. Also, the downdrift shore may experience
              increased erosion if it was formerly supplied with material eroded
              from the now protected area.     If a beach is to be maintained in
              front of a revetment, additional structures such as groins or
              detached breakwaters may be required.

                   A revetment consists of an armor layer, filter and toe. The
              armor must resist the waves, and the slope must be sufficiently
              flat to provide stability. Typical armor materials include quarry-
              stone and 'various concrete blocks. The filter supports the armor
              against settlement, provides drainage of groundwater through the
              revetment, and prevents the retained soil from being washed through
              the armor layer by waves or groundwater     seepage.   Toe protection
              prevents displacement of the seaward edge   of the revetment.

                   Overtopping by green water (not white spray) may cause erosion
              at the top of the revetment.      Problems from overtopping can be
              minimized by choosing a structure height    that is greater than the

                                                24

            expected runup height, or by providing an overtopping apron at the
            top of the revetment.

                 Flanking is another potential problem that can be prevented by
            tying each end of the revetment into adjacent shore protection
            structures or the existing bank. However, if the bank recedes, the
            ends will have to be periodically extended to maintain contact.

            BREAKWATERS

                 Breakwaters are constructed offshore to dissipate the energy
            of approaching waves and form a protected shadow zone on their
            landward sides.    (Figure 9).   The ability of waves to transport
            sediment is a function of the wave height-squared, so a relatively
            modest decrease in incoming wave heights can have a major effect on
            sediment transport. For instance, if incoming waves are reduced to
            70% of their original height after passing a breakwater, their
            ability to move sediment will decrease to 0.70 x 0.70 or 49% of
            their original capacity.       Therefore, longshore-moving littoral
            drift will tend to accumulate behind the structure. The ability of
            a breakwatpr to trap sand is a function of its distance offshore,
            length parallel to shore, porosity, and spacing (where more than
            one breakwater is used).

                                           ORIGINAL
                                           SHORELINE                DOWNDRIFT
                                                                    EROSION

                                                     1_@RESULTING SHORELINE
                                                -.Ole     (NATURAL ACCRETION)
               APPROACHING
               WAVE CRESTS

                                                 BREAKWATER

                          Figure 9        Plan View of a Breakwater
                                    """rM 0 C @Al 1A1 A 'I

                                              25

                            If accretion continues until the breakwater is joined to the
                    shore, the resulting system would act as a large groin that would
                    totally block the sand supply to the downdrift beach. This could
                    cause significant erosion damages. Therefore, the area landward of
                    the breakwater.should be partially filled with sand after construc-
                    tion is completed. This may allow sand to continue past the struc-
                    ture and on to the downdrift beach without causing serious erosion
                    problems.

                            Breakwaters are either fixed or floating. Fixed breakwaters
                    are large masses of heavy material that rest on the bottom. Float-
                    ing breakwaters are constructed of buoyant materials such as logs,
                    hollow concrete boxes and scrap rubber tires. The latter are most
                    popular because of their durability and ready, no-cost availa-
                    bility. Floating breakwaters are generally effective in sheltered
                    waters where short-period (less than five seconds) waves are dis-
                    sipated as they pass floating structures.                                Such waves have short
                    lengths that may be less than the width of the breakwater.

                    GROINS

                           Groins are constructed perpendicular to shore and extend,
                    finger-like, out into the water. Used singly or in groups known as
                    groin fields, they trap sand or retard its longshore movement
                    (Figure 10).           Sand tends to accumulate on the updrift side of a

                                                                       WAVE CRESTS

                           NO rE.
                             rhe resulting shoreline will
                             gradually transition to Ineel
                            the original shoreline on
                            either side of the groin field

                                                   BREAK POINT
                                                   FOR LARGE WAVES

                                                             X*M

                                                     RESULTING SHORELINE
                                                        (pre-f illed)

                                       ORIGINAL                             RESULTING
                                       SHORELINE                            SHORELINE
                                                                            (natural accretion)

                                                Figure 10               Effects of Groins

                                                                          26

             groin while erosion occurs downdrift. This will cause the shore-
             line to rotate and aline itself with the crests of the incoming
             waves, gradually decreasing the angle between the waves and the
             shore. In turn, the longshore transport rate will decrease and the
             shoreline will stabilize. The fillets of sand that collect on the
             updrift sides of the groins act as protective buffers. Storm waves
             attack these accumulations first, before reaching the unprotected
             backshore.

                  Without the sand fillets, groins cannot protect the shoreline
             from wave action, nor are they effective where the waves approach
             perpendicular to shore.     Groin installations also require an ade-
             quate sand supply and are not effective where the littoral mater-
             ials are finer than sand.     Silts and clays tend to move in suspen-
             sion and are not retained by groins on the beach.
                  When a groin is first built, the sand trapped on its updrift
             side is no longer available to downdrift beaches and erosion may
             result.   When the updrift fillet is completely formed, the sand
             will pass around or over the groin to the downdrift shore, but at a
             slower rate than before it was built. If erosion of the downdrift
             shore is unacceptable (it usually is), an alternative is to build
             more than one groin and fill the area between with sand. This
             minimizes the downdrift damages and limits the erosion at the
             groin's shoreward end.

                  Groins can be built either high or low with respect to the
             existing beach profile. High groins effectively block the supply
             of sand to downdrift beaches, provided sand cannot pass through
             them.  Low groins, built to be overtopped by waves either during
             storms or at a given tide level, permit sand to pass over them and
             nourish downdrift beaches.

                  A groin's length must be sufficient to create the desired
             beach shape while still allowing sand to pass around its outer end.
             If a groin extends seaward past the breaker zone, the sediment
             moving around the structure may be forced too far offshore to
             return to the adjacent downdrift beach. If it is too short, it may
             not trap enough sand to provide the desired beach.

                  The correct spacing of individual groins within a field is
             often difficult to determine and is a function of their length and
             the desired final shoreline shape.       If groins are too far apart,
             excessive erosion can occur between them.       If spaced too closely,
             they may not function properly. This is particularly true for long
             groins where sand passing around their ends must follow a curved
             path back to the beach. If the groins are too close toqether, the
             sand will be unable to reach the beach before it is again forced
             seaward by the next downdrift groin.

                  A groin must be built to resist wave forces, currents, the
             impact of floating debris, and earth pressures created by the dif-
             ference in sand levels on both sides.       As with other structures,

                                                27

              groins must resist toe scour, and must be constructed to prevent
              failure due to flanking (erosion at their landward end).

              BEACH FILLS

                  Beach fills are quantities of sand placed on the shoreline by
              mechanical means, such as dredging from offshore deposits or over-
              land hauling by trucks. The resulting beach provides some protec-
              tion to the area behind it and also serves as a valuable recrea-
              tional resource.

                  The beach fill functions as an eroding buffer zone.          Its
              useful life will depend on how quickly it erodes; a rapid succes-
              sion of severe storms can completely eliminate a new fill in a
              short time.  The owner must then be prepared to periodically re-
              nourish (add more fill) as erosion continues. Beach fills gener-
              ally have relatively low initial costs but periodic maintenance
              costs needed for adding new fill.

              VEGETATION

                  A planting program to establish desired species of vegetation
              is an inexpensive approach to shoreline protection and erosion
              control. Depending on where stabilization is desired, species from
              one of two general groups should be selected to insure adequate
              growth.

                  Found on parts of shorelines flooded periodically by brackish
              water, species of grasses, sedges, and rushes occur in marshes of
              moderate to low energy shorelines.  once extensive and widely dis-
              tributed, marsh areas were viewed  in the past as useless and were
              subjected to filling and diking.    However, their destruction has
              lessened as their importance in    the ecosystem and to shoreline
              protection has been realized.

                  upland species (shrubs and trees but particularly grasses) are
              especially adapted to growing in the low-nutrient, low-moisture
              environment of the higher beach elevations, where they are subject
              to abrasion by windblown sand particles. Used to trap sand and
              stabilize the beach, upland vegetation also improves the beauty of
              a shoreline, prevents erosion during heavy rain, diminishes the
              velocity of overland flow, increases the soil's infiltration rate,
              and provides a habitat for wildlife.

                  Even though vegetation provides significant help in stabiliz-
              ing slopes and preventing erosion, vegetation alone cannot prevent
              erosion from heavy wave action or prevent movement of shoreline
              bluffs activated by groundwater action. In these instances, struc-
              tural devices augmented with vegetation are recommended.
                  The effectiveness of vegetation is also limited by character-
              istics of the site.    For instance, the site requirements which

                                              28

            determine the effectiveness of 'a tidal marsh planting include:
            elevation and tidal regime, which determine the degree, duration,
            and timing of plant submergence; slope of the site; exposure to
            wave action; type of soil; salinity regime; and oxygen-aeration
            times. Plants which are specially adapted for higher beach eleva-
            tions must tolerate rapid sand accumulation, flooding, salt spray,
            abrasion by wind-borne sand particles, wind and water erosion, wide
            temperature fluctuations, drought, and low nutrient levels. Appro-
            priate species also vary with geographical location, climate, and
            distance from the water (vegetative zone).

            INFILTRATION AND DRAINAGE CONTROLS

                 Infiltration and drainage controls are often needed to achieve
            stability along high bluff shorelines. Although many factors lead
            to slope stability problems, the presence of groundwater is one of
            the most important, since the majority of slope failures and land-
            slides occur during or after periods of heavy rainfall or increased
            groundwater elevations.    Infiltration controls prevent water from
            entering the ground, while drainage controls remove water that is
            already present in the soil.

                 Infiltration can be controlled by appropriate ditches and
            swales, and by sealing the ground surface.        Surface cracks that
            develop when a slope begins to f ail can be an easy path for water
            to enter, exert hydrostatic pressures, and lead to further insta-
            bility.   Such cracks should be promptly filled with compacted,
            relatively impermeable soil (preferably clay) to reduce the poten-
            tial for such detrimental effects.

                 Drainage of the subsurface can be accomplished using vertical
            or horizontal drains.    Standard design techniques and methods are
            described in civil engineering references such as Winterkorn and
            Fang (1975).

            SLOPE FLATTENING

                 A bluff slope may be flattened to enhance its stability when
            adequate room exists, and there is no interference with the desired
            land use.   Freshly excavated slopes should be planted to prevent
            erosion from surface runoff.     It may also be necessary to build a
            revetment or bulkhead at the toe of the slope to protect against
            wave action.

            PERCHED BEACHES

                 A perched beach (Figure 11) combines a low breakwater or sill
            and a beach fill perched, or elevated, above the normal level.

                                              29

                             SPLASH
                             APRON
                     MHW

                     ROCK
                     SILL                             BEACH FILL

                             FILTER
                            CLOTH

                                    CROSS- SECr101V 4-A

                                                       MHW

                                                       BEACH FILL
                            ROCK SILL

                                         PLAN VIEW

                                Figure 11       Perched Beach

             This alternative provides a broad buf fer against wave action while
             offering a potentially excellent  recreational site. The sill can
             be constructed of various materials, but it must be impermeable to
             the passage of the retained beach sand by using, for instance, a
             filter cloth behind and beneath the structure. The cloth prevents
             the fill from escaping through any large voids in the sill and also
             stabilizes the structure against settlement. While a graded stone
             core could also be used in a rock sill in place of filter cloth,
             the limited height of such sills generally precludes use of multi-
             layered structures of this kind.   The figure also shows a splash
             apron which is provided to prevent scour and erosion of the beach
             fill from overtopping waves.
                                                               Al

                                              30

                 Perched beaches can be provided where offshore slopes are mild
            enough to permit the use of a sill in shallow water at a reasonable
            distance from shore.

            STRUCTURES AND FILLS

                 In addition to perched beaches, fills can also be incorporated
            in groin systems and with breakwaters.      in fact, auxiliary fills
            are almost mandatory in most cases, otherwise serious erosion
            problems can occur downdrift.

            STRUCTURES AND VEGETATION

                 While vegetation is one means of controlling shoreline ero-
            sion, its most serious deficiency is its restriction to areas of
            limited fetch because it cannot become established in heavy wave
            environments.   Vegetation can be used in areas experiencing con-
            siderably heavier wave activity, however, if it is placed in the
            shadow of a structure such as a breakwater. The use of temporary
            structures is particillarly appealing because they provide protec-
            tion while the plants need it, and can then be removed later when
            the plantings have matured.

                                              31

                                        THE DESIGN PROBLEM

              FUNCTIONAL DESIGN

              Shoreform Compatibility

                   Certain approaches are better suited to particular shoreline
              configurations than others.      It is important to choose a method
              appropriate to the dominant shoreform at the site.

                   Bluff Shorelines.     The no action alternative can be appro-
              priate for blufFs---slr-nce it does not disrupt natural shoreline pro-
              cesses and requires no investment for protective structures.
              Eventually, however, the property may be totally destroyed by ero-
              sion.  While relocation does not disrupt shoreline processes, and
              it can permanently eliminate any threat to buildings, it can cost
              as much as or more than a protective structure.            Bulkheads are
              ideally suited, either for full-height retention of low bluffs, or
              as toe protection for high bluffs. Constructed of readily avail-
              able materials and easily repaired if damaged, they are parti-
              cularly useful where offshore slopes are steep. They can, however,
              induce toe scour and loss of beach material. Revetments are mar-
              ginally effective in bluff situations.         Low bluf fs that can be
              flattened to a stable slope may be effectively protected by revet-
              ments, but high bluffs generally cannot be regraded.           Revetments
              can protect the toes of high bluffs, either alone, or in conjunc-
              tion with another device. Breakwaters reduce wave energy reaching
              the bluff but do not provide positive toe protection.           They may
              build or maintain a beach (if an adequate sand supply exists) which
              provides some protection against normal waves, but would be inef-
              fective against storm waves. Use of breakwaters generally requires
              gentle offshore slopes. Groins protect only to the extent they can
              build or hold a beach.       since they require a sand supply, they
              would not work in an area of clay or silt bluf fs unless sand were
              imported. Beach fills provide some protection against normal wave
              action but would be ineffective during storms.         Vegetation would
              provide little protection until well established and even then,
              does not positively protect against large storm waves.            Drainage
              controls are mandatory if groundwater adversely affects slope sta-
              bility. However, they provide no toe protection and can be expen-
              sive.   Slope flattening provides     a permanent solution for slope
              stability problems, but does not protect against continued wave
              action. It also requires adequate     room at the top of the bluff for
              the slope. A perched beach would      protect against normal waves but
              would be ineffective during storms. A combination approach can be
              the best solution. For instance, drainage controls should be used
              as needed, possibly with slope flattening. Toe protection could be
              provided with a revetment and a fronting sand beach to provide
              additional protection (provided offshore slopes are mild). Vegeta-
              tion planted on the regraded slope would prevent erosion from
              runoff,, and other species could be used to stabilize the beach
              fill.
                   Sand Beaches.    The no action and relocation alternatives are
              applicable as they were for bluffs. Bulkheads are generally inap-

                                                 33

              propriate unless an elevated featurej, such as a promenade or
              parking lot, is needed.     Vertical bulkheads induce toe scour and
              wave reflections, and could cause erosion of the beach fronting the
              bulkhead.   Revetments are better for protecting features directly
              behind the beach since they absorb wave energy better and are more
              flexible when settlement occurs.      They have an adverse aesthetic
              effect on the beach, however, and they can limit use or access to
              the shore.    Use of   revetments by a single landowner is often a
              problem because they   are subject to flanking. Breakwaters are also
              well suited because    they trap and hold sand moving along-, on- or
              offshore.   They can cause extensive downdrift damages, however,
              because the trapped    sand cannot reach adjacent beaches. They are
              also expensive to build. Groins can effectively build beaches on
              their updrift sides but can also cause accelerated downdrift ero-
              sion.  Their functional behavior is complex and difficult to pre-
              dict.   Beach fills retain the natural form and character of the
              beach and enhance its recrdational potential.         Local sources of
              suitable sand are not always available, however,      and fills require
              periodic renourishment.     Vegetation, effective in many sheltered
              areas, has low initial costs and enhances the natural appearance
              and beauty of the shoreline.       Unfortunately, foot and vehicular
              traffic damage plantings.     Drainage controls and slope flattening
              are not applicable.     Perched beaches can be used in some areas
              where fills alone would be too large to be economical, or where
              larger wave action is a problem. Combination approaches are often
              excellent, such as a perched beach that is further stabilized by
              vegetation.

                   Wetlands.   Structures built near wetlands are usually placed
              at a low bluf f or beach behind the marsh. For protection of the
              marsh itself, vegetation is the only appropriate alternative. To
              assist in establishing plantings, however, small temporary break-
              waters may be required. Beach fills or perched beaches may also be
              used to provide , a suitable substrate for planting in some areas.

              Applicability to Shoreline Uses

                   Some methods lend themselves more readily than others to
              particular shoreline uses. It is important to choose a method that
              performs its function and does not interfere with the planned use
              of *the shoreline.   No action obviously does not enhance shoreline
              uses, although continued erosion may have an adverse impact.
              Relocation involves similar considerations.       Bulkheads create an
              access problem unless stairs are provided. Vertical structures may
              also cause wave reflections that can erode the remaining beach
              material. Bulkheads are necessary when some water depth for boat-
              ing activities is needed at the shore.         Revetments of randomly
              placed rough stone may hinder access to the beach.        Smooth struc-
              tures, such as concrete blocks, cause less difficulty for walkers.
              Breakwaters provide an area sheltered from waves, but they can
              hinder circulation and cause water quality problems. Beaches built
              behind breakwaters have enhanced recreational potential.            Rough
              stone structures may provide an improved habitat for certain fish

                                                 34

             species but may be hazardous to climbers. High structures may also
             intrude on the view of the water and be aesthetically undesirable.
             Groins may hinder travel along the beach, but any sand they trap
             improves the beach conditions.     Beach fills enhance recreational
             uses of the shore, but increased turbidity during construction can
             temporarily harm certain fin and shellfish species.         Vegetation
             greatly improves the natural habitat but hinders other uses of the
             beach because traffic through the plantings must be restricted.
             Drainage controls have little impact on shoreline uses and slope
             flattening reduces the available land at the shore.            Perched
             beaches provide a recreational beach. A vertical sill may 'pose a
             hazard to bathers because of the sudden step to deeper water, but
             it may provide improved access for fishing. A rock sill may pro-
             vide a natural habitat for fin and shellfish and may not be as
             hazardous to bathers.

             Conditions in the General Area

                  Conditions in the local area can strongly influence the selec-
             tion of an alternative.    One of the most important considerations
             is the possible effects on downdrift properties. Accretion devices
             (breakwaters and groins) trap sand moving along the beach and tend
             to starve the downdrift shoreline.    If this would cause damages to
             neighboring properties,  the area behind the breakwater or updrift
             from the groin must be   partially filled so that littoral material
             bypasses the structure,  and downdrift damages are avoided.

                  shoreline composition is also important. Accretion devices do
             not function in areas where little sand is in transit because they
             do not sufficiently calm the water to permit settlement of silts
             and clays.    Slopes and soil composition are also important for
             determining appropriate plant species.

                  Finally, climatic and other environmental conditions must be
             considered.   Plant species obviously must be planted where the
             climate permits survival and growth. Salinity is critical for many
             species which can only tolerate changes of salinity within a narrow
             band. Warm salt water more easily corrodes steel and other metals
             than cold fresh water.     Warm salt water is also the habitat of
             marine borers that attack submerged timber structures.        On the
             other hand, fresh water lakes freeze in the winter, subjecting
             structures to large forces and abrasion from ice sheets.      In some
             areas this may require more sturdy construction than would be
             required for resisting wave action at the site.

             Summary

                  The factors relating each available alternative to shoreform
             and shoreline use are summarized on Tables 1 and 2.

                                               35

                                                                      Table

                                                     METHODS APPLICABLE TO VARIOUS SHOREFORMS

                              Alternative*               High Bluffs         Low Bluffs          Beaches           Wetlands
                    No Action                           Rarely             Rarely             Rarely             Rarely
                    Relocation                          Sometimes          Sometimes          Sometimes          Sometimes
                    Bulkheads                           Usually            Almost always      Sometimes          Rarely
                    Revetments                          Sometimes          Almost always      Almost always      Rarely
                    Breakwaters                         Rarely             Rarely             Almost always      Sometimes
                    Groins                              Almost.never       Almost never       Almost always      Almost never
                    Beach Fills                         Almost never       Almost never       Almost always      Rarely
                    Vegetation                          Almost never       Almost never       Sometimes          Almost always
                    Infiltration and Drainage
                       Controls                         Almost always      Usually            Almost never       Almost never
                    Slope Flattening                    Rarely             Usually            Almost never       Almost never

                    Perched Beaches                     Rarely             Rarely             Almost always      Sometimes

                     Applicability is for the alternative used alone in    the given situation. Combination devices are
                     not included.

                                                                      Table 2

                                               COMPATIBILITY OF ALTERNATIVES WITH SHORELINE USES

                              Alternative                 Strolling          Bathing            Fishing            Boating

                    No Action                           Sometimes          Sometimes          Usually            Usually

                    Relocation                          sometimes          Sometimes          Sometimes          Sometimes

                    Bulkheads                           Usually            Sometimes          Almost always      Almost always
                    .Revetments                         Usually            sometimes          Usually            Usually

                    Breakwaters                         Almost always      Almost always      Almost always      Usually

                    Groins                              Usually            Almost always      Almost always      Usually

                    Beach Fills                         Almost always      Almost always      Usually            Almost always

                    Vegetation                          Almost never       Almost never       Almost always      Rarely

                    Infiltration and
                      Drainage Controls                 Almost always      Almost always      Almost always      Almost always
                    slope Flattening                    Almost always      Almost always      Almost always      Almost always
                    Perched Beaches                     Almost always      Almost always      Almost always      Usually

                 STRUCTURAL DESIGN

                          If the chosen alternative involves construction of a physical
                 shore protection device, several key problems must be resolved
                 before an adequate structural design is completed. The first step
                 is an evaluation of the potential water level and design wave
                 height at the site.                  Other considerations include toe protection,
                 filtering, flank protection, structure height, and various environ-
                 mental factors.

                                                                         36

             Water Levels

                  A design water level must be determined before the wave height
             used to design structures can be found.            In tidal waters, the
             elevation of the mean spring or diurnal tide is a sufficient star-
             ting point for low cost protection.          Table 3 is reproduced from
             Tide Tables published by the National ocean Survey (See Water
             fe__Veli___1T_nthe OTHER HELP Section).   For instance, at Station       37,
             6R-ford, Maryland, the mean tide range is 1.4 feet, the spring         range
             is 1.6 feet, and the mean tide level is +0.7 feet above chart          datum
             (MLW). The average spring tide, therefore, is +1.5 feet above MLW
             (Figure 12).    An increment should be added to account for storm
             setup effects. Local experience should dictate, but values of two
             or three feet are probably reasonable for storm setup.

                  Attention should be drawn to the use of Mean Low Water (MLW)
             as datum in the previous discussion. This has been the datum used
             by the National Ocean survey in the past for east coast navigation
             charts.    In the future, however, the NOS will begin to adopt Mean
             Lower Low Water (MLLW) as datum for all nautical charts in the
             United States.      This change will occur gradually as charts are
             periodically revised and reissued.

                   On the Great Lakes, the Monthly Bulletin of Lake Levels for
             the Great Lakes (see Water Leve_ls-@1_nthe Other Help Sec on) sum-
             i-ar-ii-eswat-e-F-Tevels for the previous year and the current year to
             date, as well as projected lake levels for the next six months.
             For each lake, a curve is also given for the long-term average lake
             level (1900 to the present) (See Figure 13).           A suggested design
             water level is the greater of (a) the water level midway between
             the long-term average and the recorded maximum average monthly
             water level or (b) the highest monthly water level that has oc-
             curred during the preceding year. For instance, on Lake Michigan,
             the highest average water levels occur in July when they are about
             2.0 feet above chart datum (576.8 feet). (Low Water Datum (LWD) is
             +576.8 feet IGLD for Lake Michigan.) The maximum observed monthly
             water level for July on Lake Michigan was observed in 1974 at +4.2
             feet. A water level midway between them is +3.1 feet. The maximum
             observed monthly water level during the previous year was +3.0
             feet, so the chosen water level should be the greater of the two or
             +3.1 feet (579.9 feet).

                   Storm setup or seiche values should be added to obtain a final
             water level.     Figure 14 contains suggested values from Help Your-
             self [U. S. Army Corps of Engineers (1978d)] superimposed on a map
             of the Great Lakes. The design lake level, therefore, will be the
             sum of the lake level found in the previous step and the storm
             setup value.

             Wave Heights

                   Waves at a site are generated either by wind action or moving
             vessels. At most locations, however, wind action is more critical

                                                  37

                                                                                                                     POSITION                   DIFFERENCES                 RANGES
                                                  No.                                PLACE                                                   Time            Height                        Mean
                                                                                                                                                                                           Tide
                                                                                                                     Lot.         Long.                                     Mean   Spring  Level

                                                                                                                     .  I         . I                                       feet   feet    feet
                                                                   VIRGINIA - Continued
                                                        Chesapeake Bay, Eastern Shore                  Con.          N.           W. on HAMPTON ROADS, p.88
                                                                    Time meridian, 75'W.
                                               1959     Occohannock Creek            -------------------             37 33        75 55 +2   02 +2  32     -0.8      0.0    1.7    2.0     0.9
                                               1961     Pungoteague Creek            -------------------             37 40        75 50 +2   22 +2  37     -0.8      0.0    1.7    2.0     0.8
                                               1963     Onancock, Onancock Creek            ------------             37 43        75 45 +2   52 +3  09     -0.7      0.0    1.8    2.2     0.9
                                               1965     Watts Island--7       ---------------------                  37 48        75 54 +2   59 +3  02     -0.9      0.0    1.6    1.9     0.8
                                               1967     Tangier Sound Light          -----------------               37 47        75 58 +2   51 +2  48'*0.64      *0.64     1.6    1.9     0.8
                                               1969     Muddy Creek Entrance         ----------------                37 51        75 40 +3   14 +3  43     -0.3      0.0    2.2    2.6     1.1

                                                                              MARYLAND
                                                              Chesapeake Bay, Eastern Shore
                                               1971     Ape Hole Creek, Pocomoke Sound               ------          37 58        75 49 +3   24 +3  48     -0.2      0.0    2.3    2.8     1.1
                                                        Pocomoke River
                                               1973           Shelltown       -----------------------                37 59        75 38 +3   29 +4  06     -0.1      0.0    2.4    2.9     1.2
                                               1975           Pocomoke City          -------------------             38 05        75 34 +5   46 +6  05     -0.9      0.0    1.6    2.0     0.8
                                               1976           Snow Hill, city park          ------------             38 10        75 24 +7   32 +7  43     -0.6      0.0    1.9    2.3     1.0
                                               1977     Janes Island Light           ------------------              37 58        75 55 +3   51 +3  50     -0.7      0.0    1.8    2.2     0.9
                                               1979     Crisfield, Little Annemessex River-                          37 59        75 52 +3   47 +3  55     -0.5      0.0    2.0    2.4     1.0
                                               1981     Long Point, Big Annemessex River               ----          38 03        75 48 +4   16 +4  36     -0.4      0.0    2.1    2.5     1.0

                                               1983     Teague Creek, Manokin River              ---------           38 06        75 50 +4   35 +4  55     -0.4      0.0    2.1    2.5     1.0
                                               1985     Ewell, Smith Island          -----------------               38 00        76 02 +3   56 +4  21  *0.64     '0.64     1.6    1.9     0.8
                                               1987     Solomons Lump Light          -----------------               38 03        76 01 +4   13 4-4 15     -0.8      0.0    1.7    2.0     0.8
                                               1989     Holland Island Bar Light            ------------             38 04        76 06 +4   13 +4  20  *0.56     *0.56     1.4    1.7     0.7
                                               1991     Sharkfin Shoal Light         ----------------                38 12        75 59 +4   43 +4  56     -0.3      0.0    2.2    2.6     1.1
                                               1993     Great Shoals Light, Monie Bay               -------          38 13        75 53 +4   57 +5  12     -0.2      0.0    2.3    2.8     1.2
                                                        Wicomtco River
                                               1995           Whitehaven      ----------------------                 38 16        75 47 +5   24 +5  37     -0.1      0.0    2.4    2.9     1.2
                                               1997           Salisbury       -----------------------                38 22        75 36 +6   18 +6  14     +0.5      0.0    3.0    3.6     1.5
                                                        Nanticoke River
                                               1999           Roaring Point          -------------------             38 16        75 55 +4   57 +5  25     -0.2      0.0    2.3    2.8     1.2
                                               2001           Vienna   --------------------------                    38 29        75 49 +7   30 +7  36     -0.2      0.0    2.3    2.8     1.2
                                               2003           Sharptown       -----------------------                38 32        75 43 +8   16 +8  18     0.0       0.0    2.5    3.0     1.3
                                               2005     Fishing Point, Fishing Bay             ----------            38 18        76 01 +5   01 +5  24     0.0       0.0    2.5    3.0     1.2
                                               2007     Hooper Strait Light          -----------------               38 14        76 05 +4   52 1+4 57     -0.8      0.0    1.7    2.0     0.8
                                                                                                                                             on BALTIMORE, P.80
                                               2009     Hooper Island Light          -----------------               38 15        76 15 -5   07 -5  23     +0.4      0.0    1.5    1.8     0.7
                                               2011     Barren Island         -----------------------                38 20        76 16 -4   52 -5  07     +0.2      0.0    1.3    1.5     0.6
                                                        Little Choptank River
                                               2013           Taylors Island, Slaughter Creek-                       38 28        76 18 -3   27 -3  14     +0.2      0.0    1.3    1.5     0.6
                                               2015           Woolford, Church Creek           ----------            38 30        76 10 -3   25 -3  10     +0.3      0.0    1.4    1.6     0.7
                                               2017           Cherry Island, Beckwiths Creek-                        38 34        76 13 -3   21 -3  11     +0.2      0.0    1.3    1.5     0.6
                                               2019           Hudson Creek           --------------------            38 35        76 15 -3   49 -3  31     +0.3      0.0    1.4    1.6     0.7
                                               2021     Sharps Island Light          -----------------               38 38        76 23 -3   51 -4  00     +0.2      0.0    1.3    1.5     0.6
                                                        Choptank River
                                               2023           Choptank River Light          ------------             38 39        76 11 -3   17 -3  18     +0.3      0.0    1.4    1.6     0.7
                                               2025           Cambridge       -----------------------                38 34        76 04 -2   54 -2  50     +0.5      0.0    1.6    1.8     0.8
                                               2027           Choptank        ------------------------               38 41        75 57 -2   13 -1  58     +0.5      0.0    1.6    1.8     0.8
                                               2029           Dover Bridge           --------------------            38 45        76 00 -0   57 -0  56     +0'.6     0.0    1.7    2.0     0.8
                                               2031           Denton   --------------------------                    38 53        75 50 +0   13 +0  22     +1.1      0.0    2.2    2.5     1.1
                                               2033           Greensboro      ----------------------                 38 58        75 49 +1   18 +1  08     +1.4      0.0    2.5    2.9     1.2
                                               2035           Wayman Wharf, Tuckahoe Creek             ----          38 53        75 57 +0   53 +0  25     +1.3      0.b    2.4    2.8     1.2
                                                        Tred Avon River                                              I               I                  I                   I      I
                                               2037           Oxford   --------------------------                    38 42        76 10 1-3  05- -3 00     +0.3      0.01   1.4    11.6    0.7   1
                                               2039           Easton Point           --------------------            38 46        76 06 -2   59 -2  50     +0.5      0.0    1.6    1.8     0,8
                                               2041     Deep Neck Point, Broad Creek               --------          38 44        76 14 -3   10 -3  01     +0.3      0.0    1.4    1.6     0.7
                                               2043     St. Michaels, San Domingo Creek                -----         38 46        76 14 -3   08 -3  06     +0.3      0.0    1.4    1.6     0.7
                                               2045     Avalon, Dogwood Harbor            --------------             38 42        76 20 -3   08 -3  03     +0.2      0.0    1.3    1.5     0.6
                                               2047     Poplar Island         -----------------------                38 46        76 23 -3   12 -3  18     +0.1      0.0    1.2    1.3     0.6
                                               2049     Ferry Cove, Eastern Bay             -------------            38 46        76 20 -3   01 -3  04     -0.1      0.0    1.0    1.2     0.5

                                                                              Table 3                                Sample          Tide Table
                                                                        [U.-S. Department                            of Commerce                    (1976)]

                                                                                                                     38

                                                              + 1.1MLW

                                                              + 1.4' M LW
                                                                 (MEAN HIGH WATER)

                     0. 7'   0.8' (MEAN SPRING RANGE  2)

                                                                   MLW
                                                                (MEAN TIDE LEVEL)

                        0.7' (MEAN TIDE RANGE - 2)

                                                              +0.0' MLW

                 Figure 12        Reference Water Levels at Oxford, Maryland

                                                 39

                                                                                                                                        1980                                                                                                              1981                                                                   1982
                                                                                                                                        MAY                               OCT NOV DEC                                              MMAY JUN @ JUL AUG S                          OCT NOV '                       JANTFEB W..JUN Ft.
                                                                                I         @--- ---.,-T             - -.-,                                                 -,I                 ---                                                                      -                                         - -TE-C
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                                                                                                                                                                                                                                                          T97
                                                                                                                                                                                                                                                                                                                                                          wn 5
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                                                                                                                                                                                                                                   in

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                                                                                                                                                                                                                                   .. . .........                     ......... . ..                             ..........
                                                                                                                                                                                                                                   ..........                                                                    ... .... . . . .......
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                                                                                                                                                                                                      ioj6 -
                                                                                          T                                             77ii=i=,17-2@--                   ..... .........

                                                                                                                                        1980                                                                                                              1981                                                                   1982
                                                                                                                                                                                                                                                                                                                                                          JUN
                                                                                JAN       FEB MAR                  APR                  MAY                                                                                                                   AUG
                                                                                                                                        JUN i JUL AUG 1 SEP               OCT NOV    DEC      JAN FEB                              MMART PR KAY           UN           SEP       RT                              V_@EC JWIFEBMARI@F@              IIAIT
                                                                                                                                                                                                                                                                                                                         .. ....... .
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                                                                                                                                                                                                                                   . . . . . ...........                                                         ... ..........
                                                                                                                   -F-I                 ........... i, --                 pi
                                                                                                                                        1974                                                                                                                                                                                                   4
                                                                                                                                                                                                                                                                     . ............ .
                                                                                                                                                                                                                                                                                                                                               im                  +4
                                                                             +4
                                                                                                                                                                                                                                                                              1P.I. 77-
                                                                                                                   -IV3                                                                                                            1:                                                                            19                            3
                                                                                                                                                                                                          52 ly/3                  . ........... ....                                                            II AS2 V
                                                                                                                                                                                     1973 lo-3-ft,�
                                                                                                                                                           ...........                                    .......                  . ..........           ...... . ..
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                                                                                                                                                                                                                                                          .. . . .........
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                                                                                          LAKE-8                   MI                                                                                                              1064-"                                                                                                      '1964
                                                                             17,7                i=q.=7T-                                                                                                                                                                                                        19@4 _TM 19-
                                                                                                                                                                                              196S                                 41.96                                                                                                       2196E
                                                                                                                                                                                                                                                                       =F17
                                                                                                                                                                                                                                                          .. ........ ...

                                                                                                EXAMPLE
                                                                                          CHOOSE GREATER OF.'
                                                                                          (a) Midway between long term average (Thin Line) and highest recorded
                                                                                                  monthly level. These are points (a)
                                                                                          W Highest water level recorded in previous 12 months (Thick Line).
                                                                                                  These ore points (b).

                                                                                          LEGEND

                                                                                                                   Actual monthly water levels for post 15 months
                                                                                          =No                      Projected monthly water levels for next 6months
                                                                                          -                        Average monthly water levels; 1900 to present
                                                                             ,
                                                                                          @QAT E)                  Extreme monthly high and low water levels                                                                                                                                                     I                             tR
                                                                             4

                                                                                                                                        Figure 13                                                   Design Lake Levels
                                                                                                [After U.S. Army Corps of Engineers (1981a)j

                                                                                                                                                                                                                                   40

                                                                                                      NOTE'
                                                                                                      Values of storm setup are in feet.

                                                                  S
                                        /.0)        X,  .
                                      .0          (/.0)

                                                   41

                                                                                    (0-9) (0.8)

                                                             (2.2                                      (08) f-I* -P

                                                                                                                                                            00
                                                                                                             -0)                             ONTARIo
                                                                         0 0)                                                             X, -     (0.7)

                                                                          0-0)                                                      (4.8)                 VL

                                                                     <
                                                                     .j                                   2,0            (2.0
                                                                   0.7)                                  0)
                                                                                                                 03
                                                                                                            (19)                     P E N N.

                                                                      I N D I A N A                     0   H I o

                                                    Figure 14                   Storm     Setup values for the Great Lakes
                                                                                [After U. S. Army Corps of Engineers (1978d)]

              for design. The design wave will be the lesser of (a) the maximum
              height generated by wind acting along the critical fetch or (b) the
              maximum breaker height that can reach the site during design water
              level conditions. In other words, if the wind can produce a larger
              wave than can be supported at the site, the available depth will
              control, not the wind.

                   The height of wind-driven waves depends on several factors:
              wind speed, duration, fetch length and depth.         When considering
              wind speed, it is important to realize that there must be sustained
              wind action to effectively generate waves.        Brief gusts reaching
              high velocities do not last long enough to cause wave growth. The
              fastest-mile is a convenient way to characterize both wind speed
              and duration.    The maximum fastest-mile is the highest speed that
              occurs with a sufficient duration for the wind to travel one mile.
              In other words, a 60 mile/hour wind must last for one minute to
              travel one mile, whereas a 30 mile/hour wind must last for two
              minutes.    Figures 15 and 16 are maps of the continental United
              States, including Alaska, which display the maximum fastest-mile
              wind speed contours for 10- and 25-year return periods. For exam-
              ple, the 10-year fastest-mile wind speed at New York City is
              60 mph, and at Charleston, South Carolina it is 75 mph.

                   A brief review of the concept of return period is needed
              because the public   ,tends to be confused about its meaning.        For
              instance, when told that a device will withstand the 10-year wave
              at a site, most people will probably conclude that the structure
              will be safe for the next ten years. Or, if design wave conditions
              have occurred recently, they may assume that these will not occur
              again for another ten years.        Neither of these perceptions is
              correct.   What is really meant can be illustrated by an example.
              For instance, if over a long time (e.g., 100 years), 10 episodes
              with waves of a certain size were observed, the return period for
              that wave height, based on the available statistics, would be 10
              years (100 years of record/10 observed episodes).

                   Return periods can be used to assess the risk involved in a
              particular decision.    The probability, P,    that-a particular-event
              with return period, Tr,, will occur during     a period of time, 1, is
              given by,

                                         P    1     1        x 100                  (4)
                                                        TJ I

              Table 4 contains probabilities of occurrence (percentages). for
              events with 10- or 25-year return periods as a function of various
              project durations. For example, consider an individual who wishes
              to protect his shoreline for 10 years.         Using methods explained
              later, the designer chooses a 10-year design wave. The chance of
              experiencing the design wave during a structure's 10-year life is
              65 percent. If this is an unacceptable level of risk, the designer
              may then provide protection against a larger design wave, say 25
              years.   In that case, there is an 34-percent chance of the 25-year

                                                 42

                                90       0
                                                                                       0                                              60
                              80                                                                         0                                c
                              7       ......
                                                                     ..........           . ........                 6

                                                                                                                                 0

                                                                                  7
                                                                          ............                                         0
                                                                                                                              80

                                                                      ..........
                                    5
                                                                               1, . ........ .*                          0
                                         5                                               .........
                                      9                   6                                                i.........

                                                                    6                                 0     70           0
                                                        0                             70

                                                                                                                   8
                                    90                                         60

                                    80
                                    40                         8                                 [After Thom (1968))

                         Figure       15              Fastest-Mile Wind Speeds:10-year Return Period

                                10    7

                                00                                                                                                      70
                              80                                                                                                        80
                                                                             70

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

                                                     ......    80                                                  ......

                              6
                                                                              0                                                 0
                                                           ...... .......                                                       100
                                                                                        ...........
                                    5
                                                                                                                           00
                                      50   0                                                                             0

                                      1
                                                                          0                                  ........

                                                                                                                         100
                                                        70                        8
                                                                                                                 90
                                                                                                                 10

                                    90                            0
                                    96                                                              [After Thom (1968)]

                         Figure       16              Fastest-Mile Wind Speeds:25-year Return Period

                                                                                   43

              wave occurring during the structure's 10-year life. If this is an
              acceptable level of risk, the design can proceed on that basis.

                                           Table 4

                         PERCENT CHANCE OF DESIGN  EVENT OCCURRENCE

                      Project Life          Design Condition Return Period
                         (years)                        (years)
                                                   10                 25

                           1                       10                  4
                           2                       19                   8
                           5                       41                 18
                           10                      65                 34
                           15                      79                 46
                           20                      88                 56
                           25                      93                 64
                           30                      96                 71
                           40                      99                 80
                           50                      99                 87

                   Returning  to the problem of    the design wave,   the critical
              fetch must be   identified before it is possible to     calculate the
              wave height.   Fetch length is the distance across water that wind
              blows to generate waves. At a constant wind speed, the longer the
              fetch, the larger the generated waves, up to an equilibrium point
              beyond which there is no further wave growth unless the wind speed
              increases. Figure 17 shows a proposed site for a shore protection
              project.  The critical fetch must be determined in order to esti-
              mate the design way height. The longest fetch is labeled Q in
              the figure.   Line @b   , although shorter than Line           crosses
              significantly deeper water.
                   In general, greater depths along the fetch will cause greater
              wave heights because of decreased bottom frictional effects. The
              fetch lines on Figure 17 have been divided into a series of equal
              length segments.   As shown on the figure, by noting the depth at
              each division point, the average depth along the fetch can be
              determined.   Care should be taken, however, to avoid including
              depths which are the result of small-scale depressions or rises
              that are not typical of the area, but which the fetch line happens
              to cross.   Small features such as rocks would not significantly
              affect wave growth and should be excluded in favor of a depth that
              is more typical to that area. The average depth must also be
              adjusted to correspond with the design water level.       If, for in-
              stance, the design water level is +2.8 fee MLW, then the average
              fetch depth would be 10. 0 feet for Line 1         and 14.4 feet for
              Line

                   The final step in determining wind-driven wave heights is to
              refer to Tables 5, 6, 7, 8, and 9, and select the tables that
              bracket the average fetch depth. The wave height can then be found
              by using the fetch length and the fastest-mile wind speed. In the

                                               44

                                                           FETCH LINE                                                                                                    4

                                                                                          2
                                               DEPTHS                              DEPTHS
                                               5           6                       3              10             12@                                                            7`                    6 5
                                                                                                                   W9                                                        18 S#'.
                                                                                                                                                                               .9-
                                               1           1                       12             10          1.5--@jfa    2
                                               6           1                       18             6           .. . 9' 11
                                                                                                              '2 `- 11                                                       &....
                                               9           3                       18                                    PA                                                          R   '14-                                                       SCA
                                                                                                                                         10
                                         27                10                      14                               w     10        12                   do                         2                 4
                                         12                5                       13                                                        12 12 %-2               1
                                                                                                                                                                                                                               0
                                                                                                                                             Marke,
                                      Avg:        7.21       MLW Avg:                 11.6' MLW                                              .........
                                                                                                                                                     13

                                                                                                                                                      14
                                     Fetch Length: Fetch Lengt                                                                                                               'I 2r*                                                    NAUTICA
                                                                                                     h:
                                                                                                                                                                                              V5
                                               2.80        nm                      2. 10 nm
                                                                                                                                                   Pile PA      t:PiI*-PA'Z--- 10  12    ii,
                                                                                                                                                   12:
                                               3.20        mi                      2.40 mi
                                                                                                                                                        -7    9               36
                                                                                                                                                                  bleto    1.
                                                                                                                                                             R
                                               V,,

                                                                                                                                                                       2

                                                                                                                                                                                                                  J@
                                                                                                                                                            16.                                                        4                            3
                                               wg@                                                            R                                         - -
                                                                                                                                                                     2                                                                              4
                                                                                                                                                        14                                   -4@

                                                                                                                                         3 W
                  LrI
                                                                                              9                                                                Ito    I
                                                                                                           14                                                                                         9
                                                                                                                                                            R
                                                  9 0                                   . .......                                                                                             8
                                                                          10
                                               Z,- --% 9          lu               S*      12                                            -5                    _7
                                                                                                                           M                                                                                       2
                                                                                   10
                                                                                                                                         el
                                                                                                                                                                                                                       GI
                                          4                                                                                                            3      3
                                                                                                                                                                   2
                                                                                                                                                                                                                                  .4

                                                                                                                         7
                                                                                                                                             4143
                                                                                                                                                                                                                                   3%               ."2
                                                                                                                                20..'    18,
                                                                                                                                                   4

                                                                                                                                                   3
                                                                                                                              15
                                                                                                                                         15               Film    U
                                                                                                                                                   Doi?,.      V;
                                                                                                                                                                                                                                                    3
                                                                                                                               14
                                               Z7 Eel n                                           3                                                   @-t`fsft note 6)
                                                                                                                                             8     ..-6  4 R,i2,,
                                                           R                                                             19,                                                                           5                                      3
                                                           -4-                                                                      ::9                              atI%I-
                                                           A?'PA":                                                              @6:            3
                                                           7                                                                                                                                             s1k
                                                                                       4                                                                                                                 4
                                                    2'
                                                                      A
                                                                                                     19                           W      4                                                                                             NO    -E 8
                                                                      2- PA . .....
                                                                                      9                                                                                                                                   Bridge Creeki privately
                                                                                   14see 15ft 4 M 1                                                2
                                                                                   F
                                                                                                  . 4@                              :    4                                                                             tained channet is marked b
                                                                                   Piles PA 13         21
                                                                                                                                                                                                                       beacorls I thru
                                                                                   Figure            17                     Identification of                                    Fetch Lengths at a Site

                                                                                               Table 5

                                                                         WIND-GENERATED WAVE HEIGHTS AND (PERIODS)
                                                                        FETCH LENGTHS WITH AVERAGE DEPTHS = 5 FEET

                            Wind
                            Speed                                                              Fetch Length (miles)
                            (mph)    0.5       1.0       1.5      2.0       2.5       3.0      3.5       4.0       4.5      5.0       6.o       7.0      8.0       9.0      10.0

                            10       0.5       0.5       0.5      0.5       0.5       0.5      0.5       0.5       0.5      0.5       0.5       0.5      0.5       0.5      0.5
                                     (1.0)     (1.0)     (1.0)    (2.0)     (2.0)     (2-0)    (2.0)     (2.0)     (2.0)    (2.0)     (2.0)     (2.0)    (2.0)     (2.0)    (2.0)

                            20       0.5       0.5       1.0      1.0       1.0       1.0      1.0       1.0       1.0      1.0       1.0       1.0      1.0       1.0      1.0
                                     (1.0)     (2.0)     (2.0)    (2.0)     (2-0)     (2.0)    (2-0)     (2.0)     (2.0)    (2.0)     (2.0)     (2-0)    (2.0)     (2.0)    (2.0)

                            30       1.0       1.0       1.0      1.0       1.5       1.5      1.5       1.5       1.5      1.5       1.5       1.5      1.5       1.5      1.5
                                     (2.0)     (2.0)     (2-0)    (2.0)     (2.0)     (3.0)    (3-0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     0.0)     (3.0)

                            40       l.'O      1.5       1.5      1.5       1.5       1.5      1.5       1.5       1.5      1.5       1.5       1.5      1.5       1.5      1.5
                                     (2.0      (2.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)    (3.0)

                            50       1.5       1.5       1.5      1.5       1.5       2.0      2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0      2.0
                                     (2.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3-0)     (3.0)    (3.0)

                            55       1.5       1.5       2.0      2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0      2.0
                                     (2.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.01     (3.0)    (3-0)     (3.0)    (3.0)

                            60       1.5       2.0       2.0      2.0       2.0       2.0      2.0       2.0       2.0      2.0@      2.0       2.0      2.0       2.0      2.0
                                     (2.0      (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (4.0)    (4.0)     (4.0)    (4.0)

                            65       1.5       2.0       2.0      2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0      2.0
                                     (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3-0)    (3.0)     (3.0)     (3.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4:0)    (4.0)

                            70       2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0      2.0
                                     (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (4.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)    (4.0)

                            75       2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0      2.0
                                     (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)    (4.0)

                            80       2.0       2.0       2.0      2.5       2.5       2.5      2.5       2.5       2.5      2.5       2.5       2.5      2.5       2.5      2.5
                                     (3-0)     (3.0)     (3.0)    (3.0)     (3.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)    (4.0)

                                                                                               Table 6

                                                                         WIND-GENFRATED WAVE HEIGHTS AND (PERIODS)
                                                                        FETCH LENGTHS WITH AVERAGE DEPTHS = 10 FEET

                            Wind
                            Speed                                                              Fetch Length (miles)
                            (mph)    0.5       1.0       1.5      2.0       2.5       3 0      3 5       4 0       4 5      5 0                 7 0      8 0       9 0      10.0

                            10       0.5       0.5       0.5      0.5       0.5       0.5      0.5       0.5       0.5      0.5       0.5       0.5      1.0       1.0      1.0
                                     (1.0)     (1.0)     (1.0)    (2.0)     (2.0)     (2.0)    (2.0)     (2.0)     (2.0)    (2-0)     (2-0)     (2-0)    (2.0)     (2.0)    (2.0)

                            20       0.5       1.0       1.0      1.0       1.0       1.0      1.0       1.5       1.5      1.5       1.5       1.5      1.5       1.5      1.5
                                     (2.0)     (2.0)     (2.0)    (2.0)     (2.0)     (2.0)    (2.0)     (2.0)     (2.0)    (2-0)     (2.0)     (3.0)    (3.0)     (3.0)    (3.0)

                            30       1.0       1.5       1.5      1.5       1.5       1.5      2.0       2.0       2.0      2.0       2.0       2.0      2.0       2.0      2.0
                                     (2.0)     (2.0)     (2.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3-0)    (3.0)     (3.0)     (3-0)    (3.0)     0.0)     (3.0)

                            40       1.5       1.5       2.0      2.0       2.0       2.0      2.5       2.5       2.5      2.5       2.5       2.5      2.5       2.5      2.5
                                     (2.0)     (2.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (3-0)    (4.0)     (4.0)    (4.0)

                            50       1.5       2.0       2.5      2.5       2.5       2.5      2.5       2.5       3.0      3.0       3.0       3.0      3.0       3.0      3.0
                                     (2.0)     (3A)      (3.0)    (3.0)     (3.0)     (3.0)    (3.0)     (4.0)     (4.0)    (4.0)     (4-0)     (4.0)    (4.0)     (4.0)    (4.0)

                            55       2.0       2.5       2.5      2.5       2.5       3.0      3.0       3.0       3.0      3.0       3.0       3.0      3.0       3.0      3.0
                                     (3.0)     (3.0)     (3.0)    (3.0)     (3.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)    (4.0)

                            60       2.0       2.5       2.5      3.0       3.0       3.0      3.0       3.0       3.0      3.0       3.0       3.0      3.5       3.5      3.5
                                     (3.0)     (3.0)     (3.0)    (4.0)     (4.0)     (4.0)    (4-0)     (4.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)    (4.0)

                            65       2.0       2.5       3.0      3.0       3.0       3.0      3.0       3.5       3.5      3.5       3.5       3.5      3.5       3.5      3.5
                                     (3.0)     (3.0)     (3.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)    (4.0)

                            70       2.5       3.0       3.0      3.0       3.5       3.5-     3.5       3.5       3.5      3.5       3.5       3.5      3.5       3.5      3.5
                                     (3.0)     (3.0)     (3.0)    (4.0)     (4-0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)    (4.0)

                            75       2.5       3.0       3.0      3.5       3.5       3.5      3.5       3.5       3.5      3.5       3.5       3.5      3.5       3.5      3.5
                                     (3.0)     (3.0)     (3.0)    (4.0)     (4.0)     (4.0)    (4-0)     (4.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4.0)     (4.0)    (4.0)

                            80       2.5       3.0       3.5      3.5       3.5       3.5      3.5       3.5       3.5      4.0       4.0       4.0      4.0       4.0      4.0
                                     (3.0)     (3.0)     (4.0)    (4.0)     (4.0)     (4.0)    (4-0)     (4.0)     (5.0)    (5.0)     (5.0)     (5.0)    (5.0)     (5.0)    (5-0)

                                                                                                      46

                                                                                        Table 7

                                                                    WIND-GENERATED WAVE HEIGHTS AND (PERIODS)
                                                                   FETCH LENGTHS WITH AVERAGE DEPTHS = 15 FEET

                         Wind
                         Speed                                                          Fetch LeZ!th (miles)
                         (mph)    0 5      1 0      1 5      2 0      2 5      3 0      3 .5         0    4 5      5 0      6 0      7 0      8 0      9 0      10.0

                         10       0.5      0.5      0.5      0.5      0.5      0.5      0.5      0.5      0.5      0.5      0.5      1.0      1.0      1.0        1.0
                                  (1-0)    (1.0)    (1.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)

                         20       0.5      1.0      1.0      1.0      1.0      1.5      1.5      1.5      1.5      1.5      1.5      1.5      1.5      2.0      2.0
                                  (2.0)    (2.0)    (2.0)    (2.0)    (2-0)    (2-0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (3.0)    (3.0)    (3-0)    (3.0)

                         30       1.0      1.5      1.5      1.5      2.0      2.0      2.0      2.0      2.0      2.0      2.5      2.5      2.5      2.5      2.5
                                  (2.0)    (2.0)    (2.0)    (3-0)    (3.0)    (3-0)    (3.0)    (3-0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)

                         40       1.5      2.0      2.0      2.0      2.5      2.5      2.5      2.5      3.0      3.0      3.0      3.0      3.0      3.0      3.0
                                  (2.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)

                         50       2.0      2.0      2.5      2.5      3.0      3.0      3.0      3.5      3.5      3.5      3.5      3.5      3.5      3.5      4.0
                                  (2.0)    (3.0)    (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4-0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)

                         55       2.0      2.5      3.0      3.0      3.0      3.5      3.5      3.5      3.5      3.5      4.0      4.0      4.0      4.0      4.o
                                  (3.0)    (3.0)    (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)

                         60       2.0      2.5      3.0      3.5      3.5      3.5      3.5      4.0      4.o      4.0      4.0      4.o      4.o      4.0      4.5
                                  (3.0)    (3.0)    (3.0)    (4.0)    (4-0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5.0)

                         65       2.5      3.0      3.5      3.5      3.5      4.0      4.o      4.0      4.0      4.0      4.5      4.5      4.5      4.5      4.5
                                  (3.0)    (3.0)    (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4-0)    (4.0)    (4.0)    (5.0)    (5.0)

                         70       2.5      3.0      3.5      4.0      4.0      4.0      4.0      4.5      4.5      4.5      4.5      4.5      4.5      4.5      4.5
                                  (3.0)    (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)

                         75       2.5      3.5      3.5      4.0      4.0      4.5      4.5      4.5      4.5      4.5      4.5      5.0      5.0      5.0      5.0
                                  (3.0)    (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5-0)    (5.0)    (5.0)    (5-0)

                         80       3.0      3.5      4.0      4.0      4.5      4.5      4-.5     4.5      5.0      5.0      5.0      5.0      5.0      5.0      5.0
                                  (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5-0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)

                                                                                        Table8

                                                                   WIND-GENERATED WAVE HEIGHTS AND (PERIODS)
                                                                  FETCH LENGTHS WITH AVERAGE DEPTHS = 20 FEET

                         Wind
                         Speed                                                          Fetch Leuth (miles)
                                                                                          .5     4.0
                         (mph)    0 5      1 0      1 5      2 0      2 5      3 0      3 5               4 5      5 0               7 0      8 0      9 0      10.0

                         10       0.5      0.5      0.5      0.5      0.5      0.5      0.5      0.5      0.5      0.5      1.0      1.0      1.0      1.0      1.0
                                  (1.0)    (1.0)    (1.0)    (2.0)    (2-0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2-0)    (2.0)    (2.0)    (2.0)

                         20       0.5      1.0      1.0      1.0      1.0      1.5      1.5      1.5      1.5      1.5      1.5      1.5      2.0      2.0      2.0
                                  (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)

                         30       1.0      1.5      1.5      1.5      2.0      2.0      2.0      2.0      2.5      2.5      2.5      2.5      3.0      3.0      3.0
                                  (2.0)    (2.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (4.0)    (4.0)

                         40       1.5      2.0      2.0      2.5      2.5      2.5      3.0      3.0      3.0      3.0      3.5      3.5      3.5      3.5      3.5
                                  (2.0)    (3.0)    (3.0)    (3.0)    (3-0)    (3.0)    (3-0)    (4-0)    (4.0)    (4.0)    (4.0)    (4-0)    (4.0)    (4.0)    (4.0)

                         50       2.0      2.5      2.5      3.0      3.0      3.5      3.5      3.5      3.5      4.0      4.0      4.0      4.0      4.5      4.5
                                  (3.0)    (3-0)    (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)

                         55       2.0      2.5      3.0      3.0      3.5      3.5      4.0      4.0      4.0      4.0      4.5      4.5      4.5      4.5      4.5
                                  (3.0)    (3.0)    (3.0)    (4.0)    (4.0)    (4-6)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5.0)    (5.0)

                         60       2.0      3.0      3.0      3.5      4.0      4.0      4.0      4.0      4.5      4.5      4.5      5.0      5.0      5.0      5.0
                                  (3.0)    (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5-0)

                         65       2.5      3.0      3.5      4.0      4.0      4.5      4.5      4.5      4.5      5.0      5.0      5.0      5.0      5.0      5.5
                                  (3.0)    (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5.0)    (5.0)    (5-0)    (5.0)    (5-0)

                         70       2.5      3.5      4.0      4.0      4.5      4.5      4.5      5.o      5.0      5.0      5.0      5.5      5.5      5.5      5.5
                                  (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)

                         75       3.0      3.5      4.0      4.5      4.5      5.0      5.0      5.0      5.0      5.5      5.5      5.5      5.5      6.0      6.0
                                  (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5-0)

                         80       3.0      4.0      4.5      4.5      5.0      5.0      5.5      5.5      5.5      5.5      5.5      6.0      6.0      6.0      6.o
                                  (3-0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5-0)    (5.0)    (5.0)    (5-0)    (5.0)    (5.0)

                                                                                              47

                                                                                           Table 9

                                                                        WIND-GENERATED WAVE HEIGHTS AND (PERIODS)
                                                                      FETCH LENGTHS WITH AVERAGE DEPTHS = 25 FEET

                            Wind
                            Speed                                                          Fetch Length (miles)
                            (mph)    0 5      1 0      1 5      2 0      2 5      3 0      _3 5     4 0      4 5      5 0      6.0      7.0      8.0      9.0      10.0

                            10       0.5      0.5      0.5      0.5      0.5      0.5      0.5      0.5      0.5      0.5      1.0      1.0      1.0      1.0      1.0
                                     (1-0)    (1-0)    (1.0)    (2.0)   (2.0)     (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2.0)    (2-0)    (2.0)    (2.0)    (2.0)

                            20       0.5      1.0      1.0      1.0      1.0      1.5      1.5      1.5      1.5      1.5      1.5      2.0      2.0      2.0      2.0
                                     (2.0)    (2.0)    (2.0)    (2.0)   (2.0)     (2.0)    (2.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3.0)

                            30       1.0      1.5      1.5      2.0      2.0      2.0      2.0      2.5      2.5      2.5      2.5      2.5      3.0      3.0      3.0
                                     (2.0)    (2.0)    (2.0)    (3.0)   (3.0)     (3.0)    (3.0)    (3.0)    (3.0)    (3.0)    (3-0)    (3-0)    (4.0)    (4.0)    (4.0)

                            40       1.5      2.0      2.0      2.5      2.5      3.0      3.0      3.0      3.0      3.5      3.5      3.5      4.0      4.0      4.0
                                     (2.0)    (3.0)    (3.0)    (3.0)   (3.0)     (3.0)    (3.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4-0)    (4.0)    (4.0)    (4.0)

                            50       2.0      2.5      3.0      3.0      3.5      3.5      3.5      4.0      4.0      4.0      4.5      4.5      4.5      4.5      5.0
                                     (3.0)    (3.0)    (3.0)    (3.0)   (4.0)     (4.0)    (4-0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5-0)

                            55       2.0      2.5      3.0      3.5      3.5      4.0      4.o      4.0      4.5      4.5      4.5      5.0      5.0      5.0      5.0
                                     (3.0)    (3-0)    (3.0)    (4.0)   (4.0)     (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5-0)    (5.0)    (5.0)    (5.0)

                            60       2.0      3.0      3.5      3.5      4.0      4.0      4.5      4.5      4.5      5.0      5.0      5.0      5.5      5.5      5.5
                                     (3.0)    (3.0)    (3.0)    (4.0)   (4.0)     (4.0)    (4.0)    (4.0)    (4.0)    (4.0)    (5.0)    (5-0)    (5.0)    (5.0)    (5.0)

                            65       2.5      3.0      3.5      4.0      4.5      4.5      4.5      5.0      5.0      5.0      5.5      5.5      5.5      6.0      6.0
                                     (3.0)    (3.0)    (4.0)    (4.0)   (4.0)     (4.0)    (4.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5-0)    (5.0)    (5.0)    (5.0)

                            70       2.5      3.5      4.0      4.5      4.5      5.0      5.0      5.0      5.0      5.5      5.5      6.0      6.0      6.0      6.5
                                     (3.0)    (3.0)    (4.0)    (4.0)   (4.0)     (4.0)    (4.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5-0)    (5.0)    (5.0)    (5.0)

                            75       3.0      3.5      4.0      4.5      4.5      5.0      5.5      5.5      5.5      6.0      6.0      6.0      6.5      6.5      6.5
                                     (3.0)    (3.0)    (4.0)    (4.0)   (4.0)     (4.0)    (5.0)    (5.0)    (5-0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5-0)

                            80       3.0      4.0      4.5      5.0      5.0      5.5      5.5      6.0      6.0      6.0      6.5      6.5      6.5      7.0      7.0
                                     (3.0)    (4.0)    (5.0)    (5.0)   (5-0)     (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5.0)    (5-0)    (5-0)    (6.0)    (6.0)

                         example,             fetch line                1 was 3.@ miles                      long with an average depth of
                         10.0 feet (design wa@er level at +2.81 MLW). Assuming a                                                                            10-year,
                         fastest-mile wind speed of 65 miles/hour, the wave height                                                                         would be
                                                                                                  2 , with an average depth of 14.4
                         3.0 feet (Table 6). Along Lineo
                         feet, the wave height would be 3.5 feet (interpolating between
                         Tables 6 and 7), despite the fact that its fetch length is                                                                        only 2.4
                         miles. This should be used for design. The wave periods are given
                         in parentheses on the tables below the wave heights.                                                                                In both
                         cases, the wave period is 4.0 seconds.
                                     Alternate, more precise, methods of determining the wave
                         height and period by using shallow water wave forecasting equations
                         are given in U. S. Army Corps of Engineers (1977c) (1981b) and
                         (1981c).               The two later references will eventually supersede the
                         first and are preferred by many coastal engineering specialists.
                         Their use, however, involves more elaborate procedures so, for the
                         sake of brevity and simplicity, only the equations from the first
                         reference will be given.                                     Either the tables or the equations are
                         adequate for design of low cost shore protection.

                                     The wave height, H, is,

                                                                                                 48

                                                                 0.0125 (@F  0 42
             H = 0.283 U 2 tanh 0.530     d) 0.75  tanh                   2)         (5)
                    9                   @U2               tanh   0.530  @d  0.71
                                                                        U 2)

             and the period, T, is
                                                                 0.077 (_qFy .25
                        U              (gdY.375                         U 2
             T = 2.40 1- tanh 0.833      -         tanh                              (6)
                        9               U2                              (_gd
                                                          tanh  10. 833 U 2T*375

             where U = the wind speed in feet/second;
                   F = the fetch length in feet;
                   d = the depth in fee@;
             and   g = 32.2 feet/second .

             Note: The above equations are in dimensionless form and can be
                    used with any consistent set of units.

                  Wave heights so determined should then be checked against the
             maximum possible breaking wave at the design water level.             This
             should be evaluated using Figure 18 and the depth at the toe of the
             structure, or if appropriate, the minimum depth offshore from the
             structure.   With the design water depth at the toe of the struc-
             ture, d ; the wave period, T; and the fronting bottom slope, m; the
                     s
             breaker height, H       can be found as a function of d           For   @n-
                               ,b'
             stance, if d  s = 3.0 feet, m = 1:33, and T       4.0 secone?s,' d /gT
             0.00582, and H /d = 0.98; therefore H            3.0 x 0.98 = 2N (say
             3. 0) feet.   TR minimum depth along 'feibch line          is near Cedar
             Point where the depth is 1 foot at MLW, and 3          .@)feet under the
             design water level.     This would not control for this case (it is
             greater than d ), but it should be checked in every instance.
             Fetch line ('D &es not cross similar shoal areas.
                  If the wind-driven wave height was 3.5 feet, it should not be
             used for design because only a 3.0-foot wave can be supported-B-ased
             on the available minimum depth at the structure. The final design
             wave height, therefore, should be 2.9 (3.0) feet in this case. To
             restate the rule, the design wave height should be the lesser of
             the maximum wind-generated wave along the fetch, or thei-m-a-'ilimum
             possible. breaking wave at the structure or at points offshore.
                  Figure 19 gives appropriate locations for measuring the depth
             at the structure, d  s

                                                49

                                    3.5
                                                       I-       ff   +I-f+i-
                                    - -------- --                                Ow
                                    3.0                                                              breaker travel
                                                          III                                          distance

                                                                                      6
                                                                                                                Hb
                                                                                                                                          Design SWL
                                                                        Uff
                                                                                         . .............
                                                                                 :j           ..4. d,

                                                                                                                                        Nearshore slope
                                    2.0                      af
                               Hb
                                d

                                    1.5

             Ln
                                                                                                                                                                J.
                                             T:

                                                                                                                                                                T,
                                                                                                     MINE song=
                                    1.0
                                                                                             MEIN
                                                                                                                noun

                                    0.5

                                            ----------

                                      0     --------
                                       0         0.002       0.004       0.006       0.006        0;010       0.012        0.014       0.016       0.018       0.020
                                                                                                   d
                                                                                                   9T'

                          Figure 18                Dimensionless Design Breaker Height Versus Relative Depth at Structure
                                                            el
                                                   [Wegg         (1972)]

                   ds
                                                       ds

                                                              M

                                                    REVETMENTS

                  BULKHEADS
                                                             ds

                                                               M
                                                     GROINS

                                                                   d
                                                                    S

                                                     PERCHED BEACHES

                    BREAKWATERS

                 Figure 19      Depth at Structure for Various Devices

           Strength

                Shore protection structures must be strong, and this can only
           be achieved by using either massive and heavy components that
           cannot be dislodged by waves, or smaller components that interlock
           to form a large mass. The problem with small interlocking units,
           such as concrete blocks, is that they exhibit little reserve
           strength. That is, once damages occur, they generally progress to
           complete failure.

           Flexibility

                Flexibility is also desired because it allows structures to
           compensate for settlement, consolidation and toe scour. The revet-
           ment shown on Figure 20 illustrates this point. The massive indi-
           vidual concrete slabs could not be moved by waves, but the struc-
           ture failed because it was not able to adjust to erosion that
           occurred around the ends and through cracks between the slabs.

           Toe Protection
                   @ds
                         M

                                              __""4@ds M
                                                     r

                Toe protection is supplemental armoring of the beach surface
           in front of.a structure which prevents waves from scouring or

                                           51

                                                         21 June 1979

                       Ong,

                                                         7 August 1979
                                                        4W

                    Figure 20      Flexibility as a Structural Requirement

              undercutting it. Failure to provide toe protection invites almost
              certain failure. A typical example is shown on Figure 21.

              Filterin

                   Filtering, although one of the most important technical design
              details of shore protection structures, is probably the most ne-

                                              52

                                                        BULKHEAD
                    BULKHEAD                         (WITH TOE PROTECTION)
                  (NO TOE PROTECTION)

              SCOUR AT                                     FILTER
                TOE                                        CLOTH

                      Figure 21        Typical Example of Toe Protection

            glected, and leads to more failures than any other cause. The con-
            sequences of not providing proper filtering are illustrated on
            Figure 22. Without filtering, the soil particles are easily trans-
            ported through the armor layer, which continues to settle as the
            bank erodes. A properly designed f ilter blocks the passage of the
            soil particles while still allowing for hydrostatic pressure relief
            beneath the structure (Figure 23).

                 A filter layer can be provided through the use of either
            graded aggregates or a synthetic filter fabric.         Filter criteria
            for graded filters are covered in standard references such as
            Winterkorn and Fang (1975). Bertram        (1940) developed one widely
            used criterion as given below:
                             D15 (filter)  < 4 to 5 <  D15( filter)                (7)
                             D85 (soil)                D15 (so")

                  The left side of the equation is   intended to prevent piping of
            fine-grained soil through   the filter. That is, the 15-percent size
            of the filter material, D       (percent  finer by weight), must be no
            more than 4 or 5 times          D85  size of the protected soil. The

                                               53

                                                                                             MLWV
                          INI TIA L
                         POSITION        Soil and water posses through        GRA DED
                                         gaps between stones                   STONE
                           MLW                                               FIL TER

                                                                                                           4_/-Soil particles
                                                                                                               cannot penetrate
                                                                                                              filter.
                                                                              Water easily flows throug
                                                    @Groundwater              structure
                                                        f low

                                                                                           MLW V

                        FIAIA L                                              S)`NrHE r/C
                        POSMON           Erosion                             FIL TER
                                         continu'es                           CLOTH                                   SSW
                            M L W

                                                                                                       Synthetic filter cloth

                                                                                                Water can pass throuah filter
                                                                                                cloth but soil particles cannot

                                         Figure 22                                           Figure 23
                          Inadequate or No Filtering                                 Proper Filter Design

                    right side of the equation provides for adequate permeability of
                    the filter (several times greater than the adjacent soil).                                                 It
                    requires the D              size of the filter to be-at least 4 or 5 times the
                    D       f the soil.            This criterion should provide adequate permea-
                    bility for structural bedding layers, but may be insufficient for
                    groundwater drains.

                         . Several organizations have developed further restrictive
                    criteria for filters.                    For instance, the Bureau of Reclamation
                    allows no filter aggregates larger than 3.0 inches, and the Corps
                    of Engineers specifies that,

                                                           D
                                                             50 (filter)        < 25                               (8)
                                                             D50 (soil)

                    In other words, the D                    of the filter cannot be greater than 25
                                                        50
                    times the D             of the soil.            This is intended to insure that the
                    gradation cUves of the filter and soil are generally parallel.

                                                                         54

                  For perforated or slotted pipe, the D      of the filter must be
             greater than the hole width or slot diameteP

                                       D85 (filter)  > (1.0 to 1.2)       (9)
                                      Hole Diameter

                                      D85 (filter) >  (1.2 to 1.4)       (10)
                                      Slot Width

                  These and other criteria for graded filters are illustrated on
             Figure 24.

                  The above criteria also apply to the armor layer in relation
             to the filter layer.    That is, the armor layer must retain the
             filter layer as the filter retains the soil. In some cases, two
             filter layers may be required to provide the necessary transition
             from the soil to the armor.

                  Synthetic filter fabrics, available in woven and non-woven
             varieties, can be used in place of graded stone filters.         Woven
             cloths, manufactured of high strength nylon or other synthetic
             fibers, provide a uniform mesh with a constant opening size which
             can be matched to the soil characteristics.        Non-woven cloths,
             manufactured from masses of somewhat randomly oriented fibers
             bonded together by chemicals, heat or pressure, come in various
             standard thicknesses.    Unlike woven cloths, however, they lack
             uniform-sized openings, their principal advantage being lower cost.

                  Guidance on the selection of filter fabrics is contained in
             Plastic Filter Fabric [U. S. Army Corps of Engineers (1977a)].
             Selection is based on the equivalent opening size (EOS), which the
             Corps defines as "the number of the U. S. Standard Sieve having
             openings closest in size to the filter fabric openings". Material
             will first be retained on the sieve whose number is equal to the
             EOS. The EOS of commonly used filter fabrics is given in Table 10.
             The appropriate filter fabric should be selected as follows:

                  For granular soils with less than 50 percent by weight fines
             (minus No. 200 materials)
                            85% Passing Size of Soil        >
                          Opening Size of the E57ssieve    -

                  For other soils, the EOS should not be less than 70
             (0.0083 in.).   Furthermore, to reduce problems with clogging, no
             fabric should be used whose EOS is greater than 100 (openings
             smaller than the mesh of a No. 100 sieve). Also, no filter fabric
             should be used alone if the underlying soil contains more than 85
             percent of particles finer than the No. 200 sieve. In those cases,

                                              55

                                            CLEAR SQUARE OPENINGS                     US STANDARD SiEVE NUMBERS
                                            10. Sn2"Ihe' r'WW,W 1                     Be- 1@@ 30 40 50 70 100          200           HYDROMETER ANALYSIS
                                                                                                                       II I          TYPICAL
                                                                                                                                                  MATERIALS
                                                                                                                                                  FILTER

                                                                                                    SHEET ASPHAL
                                            so                                                      SAND,              ASTMOK)73D    10                  K
                                                                   CONCRE                                              AVERAGE
                                                                      SAN             00@                              PROPERT
                                                                                                                       IES:                       M12 CU FTIMIN
                                     W                               ASTMD633                                          ASPHALT SAND .15 .35       .03   .03
                                                                                                                       :ONCRETE SAND .3 .75       24    .07

                                                                                                                       CONCRETE GRAVEL
                                                                                                                       WTONO4 7      12           2.5  > 50
                                                                                                                                                  It
                                     W                               ICONCRETE        GRAa                             2.. 70 314    25           35 2.5
                                                                          ASTM 3 3
                                     U.                                               C                                21/2"TO I Ve* 40 52        56 1.5
                                                                        V4"TO NO.4
                                     W          Al                      2" TO 3/4"
                                                          r
                                                                        2 1/2"TO I W                                   if- APPROXIMATE FINEST LIMJT
                                            20                                                                         OF FILTER MATERIALS

                                            0
                                            100 8 6 4 3 2        108 6   -4 3         2  16 6 4 3 2                    .1 8 64 3 2   .0 1 1)      643 2 .001
                                                                                      GRAIN SIZE MILLIMETERS
                                     COWES [@SE            --I FINE I CO-A-RSTT-MOIUM               I FINE             SILT OR CLAY(PLAS          OR NON-
                                                        GRAVEL                            SAND
                                                                                                                                                  PTr TIC,
                                                                                                                                                  LAS
                                            100                          4            810 16  30 4D50 70 100           200
                                                                                                                                     RELATION     OF FILTER
                                                                                                                                                  AND BASE
                                                                \,.fINEST    LIMIT    OF
                                                                                      SAN                              D             R BASE OF    PLASTIC CLAY
                                                                   Ncol!@!!@          ESN                              658           WITH LOW PERMEABILITY,
                                            so                               ALT A                                                   CONCRETE SAND FILTER
                                                              k I ["KWILTERS
                                                                                                                                       MAY BE USED.

                                                                                                                                                  OR BASE OF
                                            )-60-                                                                                                 NONPLASTIC SILT',-
                                                                                                                                                  ROCK FLOUR
                                                                                                                                                  VARVED SILT, IN
                                                                                         D                                 D500
                                            z                                                                                                     THIS RANGE USE
                                            U. COARSEST MATERIAL                                                                                  ASPHALT SAND
                                              TO BE USED                                                                                            FILTER.
                                            z AGAINST C014CRE74
                                            U                                                                          INEST BASE
                                            W SAND FILTER LAYER
                                            1K                           i                I 1@                                       , .1(              1
                                                                      MOST FAVORA                                      FOR CONCRET
                                                                                      IT BLE                           SAND FILTER,
                                            Q. 20                        COMPOS E FILTER      -. X@                                               @4           -
                                                                                      VIb'SAND                         FOR 70% SAM;
                                                                                      30% GRAVEL DI! F                 30%GR&'El-FILTERA
                                                                     N      I I' -        - .                          9\            -            D
                                            0                        1 N I I I I . I I 1111-@-Jx I I I I
                                            106-8 6 4 3 2         108 6 4 3 2             18   6 4    3                2.1 8 6 4 3   2.01 8 6 4 3 2 .001

                                            General requirements:
                                                                        D
                                            1. To avoid head loss in filter:  015B    > 4, and permeability of filter must be large enough to suffice for the partic-
                                            ular drainage system.
                                                                                                    ;,0 F
                                                                                                    D _                D
                                                                                                    50 B               < 25, ;1 E
                                            2. To avoid movement of particles from base: D85 B < 5,                    11
                                                                                                                       5B < 20
                                            For very uniform base material (C. < 1.5): DIS F/D85 D may be increased to 6
                                            For broadly graded base material (C. > 4): ' DIS F/1315 B may be increased to 40
                                            3. To avoid movement of filter in drain pipe perforations or joints:
                                            N5 F/slot width > (1. 2 to 1. 4)          D85 F/hole diameter > (1.0 to 1. 2)
                                            4. To avoid segregation filter should contain no sizts latter than 3*-
                                            5. To avoid internal movement @bf fines, filter should have no more than 57. passing No. 200 sieve.
                                                            I
                                                                     CO                                                FT @3         FO
                                                             %                                                                                    I

                                                                                               F@
                                                                                                                       INE
                                                                                                                       S
                                                                                                                       FOR
                                                                                                                       SAI

                                            Figure 24                  Design criteria for Protective Filters
                                   [U.S. Navy, Naval Facilities Engineering Command (1971)]

                                                                                                    56

                                             Table 10

                            FILTER FABRIC EQUIVALENT OPENING SIZES

                                    Fabric                           EOS

                        Filter X                                     100
                        Laurel Erosion Control Cloth                 100
                        Monsanto E2B                                 80
                        Polyfilter X                                 70
                        Mirafi 140                                   50
                        Nicolon 66424                                50
                        Nicolon 66429                                40
                        Polyfilter GB                                40
                        Nicolon 66487                                30
                                          [U.S. Army Corps of Engineers (1977a)]
               *Note:   Manufacturer's  product lines are subject to change.
                       Check with the   supplier to verify current products and
                       specifications.

             an intermediate sand layer may provide the necessary transition
             layer from the in-situ soil to the filter fabric.

                  The Corps of Engineers also limits the gradient ratio of the
             filter fabric to a maximum of 3. This is defined as the hydraulic
             gradient through the fabric and the one inch of soil immediately
             above the fabric (i ) divided by the hydraulic gradient over the
             two inches of soil 16e`tween one and three     inches above the fabric
             (i 2).

                                        Gradient Ratio      < 3,                  (12)
                                                         12 -

             Where i and i are measured by a constant head permeability test
             conduct@d as s@lcified by the Corps in the earlier cited reference.

             Flank Protection

                  Flank protection is important because any shore protection
             structure, such as a revetment or bulkhead, is vulnerable as ero-
             sion continues around its ends.     if not prevented by flank protec-
             tion, the land eventually erodes from behind      the structure, which
             then fails to function adequately.         Figure 25 illustrates what
             happens when flank protection is not provided.

                  Return sections can be provided either        during the original
             construction or later, as erosion progresses. For instance, sheet
             pile bulkheads along low bluffs can easily be      tied into the exist-
             ing bank during the initial work. This is not generally possible
             for high bluffs.    Revetments must nearly always be progressively
             lengthened as erosion continues. They should be tied to the exis-
             ting bank or high ground during initial construction, however.

                                                57

                                                   F><1

                      EXISTING
                         RELINE               BULKHEAD--,,,
                                                Z

                                       (initial Construction)
                                                       "M"*'@@@BREA7KING@@
                                                                     WAVES

                                                                 RETREATED
                                                                  SHORE@@...___
                        ...................... . . . . ....................................
                                              BULKHEAD--\

                     BREAKING
                     WAVES            (Without Flonk Protection)

                                                     A%

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

                 RETURN                       BULKHEAD                       RETURN
                  WALLS                                                      WALLS

                            BREAKING WAVES

                                       (With Flonk Protection)

                                Figure 25       Flank Protection
                                                                             RETURN
                                                                             WAL  LS

                                                58

              Structure Height

                    Waves breaking against an inclined structure will run up to an
              elevation higher than the stillwater level depending on the rough-
              ness of the structure.      Smooth concrete surfaces experience higher
              runup than rough stone slopes.          Vertical structures also cause
              splashing and can experience overtopping. If possible, the struc-
              ture should be built high enough to preclude severe overtopping.
              White spray does little damage, but solid jets of "green" water
              should be avoided.       The required height of the structure will
              depend on the computed runup height based on the wave and structure
              characteristics. Detailed guidance is presented in Stoa (1978) and
              (1979). The runup height, R, can be found by a more. approximate
              method as given below.

                    First, find the wavelength at the structure by using either
              Figure 26 or Equation (3) with the known depth at the structure and
              the design wave period. The definition         sketch for runup is shown
              on Figure 27.     For SMOOTH impermeable       slopes, the runup, R'. is
              given in Seelig (1980) by,
                                                   (C2 \fH/ds+ C3)
                               R = HC     0.12 1!                                      (13)
                                      1 (      H )'

              where:    L =    the local wavelength from Figure 26 or Eq. (3),
                       d =     the depth at the structure (feet),
                        R =    the approaching wave height (feet), and
              Cl. C 2"  C3 =   coefficients given below.
                         Structure Slope*           C1         C2          C3

                             Vertical              0.96       0.23       +0.06
                             1 on 1.0              1.47       0.35       -0.11
                             1 on 1.5              1.99       0.50       -0.19
                             1 on 2.25             1.81       0.47       -0.08
                             1 on 3.0              1.37       0.51       +0.04

                Interpolate  linearly  between  these values for   other slopes.

                    For ROUGH slopes, Seelig    (1980) gives    the runup as,
                                          R      0.69 @    ) H                         (14)
                                                1 + 0.5

              where:                           tan 0                            (15)
                                              NFH-/ L 0
                                          L0= 5.12 T   2                               (16)
              and                         6 = the structure slope (e.g., tan e
                                               0.25 for a slope of 1V on 4H).

                                                  59

                   14

                   13

                   12

                   10
                    9-                                                              12     14
                                                                             10
                    8-                                              8
                0                                  4
                Z   7-                        3
                w                       2
                CL
                    6-

                    5-                                                WATER  DEPTH, d
                    4                                                      (f t.)

                    3-

                    2

                    I

                    0
                    0   10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
                                                   Wavelength, L (ft.)

                               Figure 26      Local Wavelength Given Depth and Period
                                              [After Giles and Eckert (1979)]

                                                                           R

                   L               ds           M

                                   if  -0

                       Figure 27       Wave Runup Definition Sketch

                 For STEPPED slopes, Stoa (1979) recommends using 70 to 75
            percent of the smooth slope runup if the risers are vertical, and
            86 percent if the edges are rounded.

                 A rough approximation of the runup height can be obtained from
            Table 11.  However, the values in the table tend to represent the
            upper bound of the available data and may result in over design.
            Equations (13) and (14) or the methods given in Stoa (1978) and
            (1979) are recommended.

                 If it is impossible or undesirable to build a structure to the
            recommended height, a splash apron should be provided at the top of
            the structure.   These are generally constructed of rock and they
            prevent the ground at the top from being eroded and undermining
            that portion of the structure.

            Environmental Factors

                 Many different materials can be used to construct shore pro-
            tection structures, including rock, concrete, timber, metal and
            plastics.  The choice often depends on the desired permanence of
            the protection.   Durable materials usually cost considerably more
            than shorter-lived materials used for temporary protection.        The
            choice of materials is important because the coastal environment is
            a harsh testing ground for all man-made structures.       Aside from
            wave forces, which are formidable in and of themselves, a host of
                                      z
                                                M

                                             61

                                       R                              m                   R
                               m              SWL wn                   1.5               2.25 H
                                            1   10                   2.5                 1 .75 H
                            SMOOTH FACE                              4.0                 1 .50H

                                                                      m                  E-
                                  .1 TR      SWL, -ai-F                - 5               1.25H
                                                             H
                                                            -L       2.5                 1.00H
                                               10                    4.0                 0.75H

                            ROUGH FACE

                                              SWL V
                               m                                       1.5               2.OOH
                                                             L

                            STEPPED FACE

                                            -SWL   V       HF
                                                                                         2.00 H

                                         10

                            V4FRT/CAL FACE
                                                W L         TH

                                                10

                                             SWI

                                              SWL

                                             Sw@L
                                       1@
                                         'o

                                     Table 11            Wave Runup Heights

                                                           62

            chemical, biological and other factors can degrade structural
            materials. A brief review of these follows.
                 Corrosion and Freezina.  Corrosion is a primary problem with
            metals in bra    h and saline water. This is particularly true in
            the splash zone, where the materials are subjected to continuous
            wet-dry cycles.  Plain carbon steel, for instance, probably has a
            life of less than five years under some conditions.        Corrosion-
            resistant steel marketed under various trade names is useful for
            some applications. Aluminum sheet piling can also be used in many
            areas in place of steel.     Stainless, galvanized, or other cor-
            rosion-protected steel, or wrought iron can be used for bolts and
            other fasteners.   However, care should be taken not to mix dis-
            similar metals in structures where they directly contact each
            other. The resulting galvanic action will.quickly corrode the more
            active metal of the pair (e.g., aluminum is more active than stain-
            less steel).

                 Concrete can be degraded by chemical reaction with salt water
            and by freeze-thaw cycles.    Guidance on producing suitable high
            quality concrete is presented in Mather (1957). Aggregates should
            be durable and not reactive with cement. Dense (cement rich) mixes
            should be used, typically about 7 bags of portland cement per cubic
            yard. Types II or V should be used in salt water, while Types I or
            II are, acceptable in fresh and brackish water.       Potable water
            should generally be used, but brackish or salt water may sometimes
            be acceptable for mass concrete.      Fresh water, however, should
            always be used for reinforced concrete.      Maximum water content
            should be no more than 5 1/2 gallons per bag of cement, including
            the moisture content of the aggregates. Finally, air entrainment
            (typically 4 to 7% of the concrete volume) is necessary to minimize
            damages from freeze-thaw cycles.

                 Marine Borer Activity. Timber structures submerged in brack-
            ish and salt water are subject to damage from marine borers. Any
            wood or timber used for bulkhead or other construction in areas of
            moderate borer activity should be treated with 20 pounds of creo-
            sote or 2.5 lbs. of preservative salts per cubic foot of timber.
            Where borer activity is severe, 20 pounds of creosote and 1.5
            pounds per cubic foot of preservative salts in a dual-treatment
            process is recommended for all lumber.      Timber piles should be
            dual-treated with 20 pounds of creosote and 1.0 pound of preserva-
            tive salts per cubic foot in such areas [American Wood Preservers'
            Association (1977)].

                 Ultraviolet Light.   The ultraviolet component of sunlight
            rapidly degrades untreated synthetic fibers such as those used for
            filter cloth or sand bags, totally deteriorating them in less than
            one season if heavily exposed. Any fabric used for shore protec-
            tion devices should be stabilized against ultraviolet light. This
            typically involves adding carbon black to the synthetic compound
            which gives the finished product a black or dark color in contrast
            to the white or light gray color of unstabilized cloth.          Even
            filter cloth covered by a structure should be stabilized since

                                             63

              small cracks or openings in the. structure could admit enough light
              to destroy the cloth.

                   Abrasion.    Abrasion damage occurs in all structures where
              waves move coarse sediments such as sand and gravel back and forth
              across their faces.     Coarse gravels and cobbles can also cause
              impact damages when hurled by large waves.      Little can be done to
              prevent abrasion damages beyond the use of      durable rock and con-
              crete as armoring in critical areas such as     along the sand line of
              sheet pile groins.     It is here that such structures typically
              experience the greatest amount of abrasion.

                   Ice Forces. Ice forces are primarily a problem on cold region
              waterbodies such as the Great Lakes.        Ice covers will typically
              vary with the size and location of the waterbody, and local cli-
              matic conditions.    Large bodies, such as the Great Lakes, usually
              develop partial ice covers, while smaller embayments within them
              may be totally covered.
                   The ice covers are never totally stationary and movement
              creates several categories of ice forces on structures.        For in-
              stance, dynamic forces result from wind and current-driven ice
              sheets or floes.    Vertical-faced structures will experience large
              horizontal forces, while inclined faces will tend to reduce the
              total force acting on the structure. Static ice forces result from
              thermal expansion and contraction of relatively stationary ice
              sheets.   Fractured ice forces arise from broken pack ice driven
              against a structure.     Uplift and drawdown forces are associated
              with the adhesion of floating ice sheets to structures.

                   Water level fluctuations caused by seiches, tides, or reser-
              voir operation can result in significant damage to pile-supported
              structures. Water level recession can cause considerable downward
              loadings that force the piles deeper into the bottom. Conversely,
              water surface rises will pull the piles upward. I As this occurs,
              the soil will collapse beneath the pile tips and will prevent
              return to their original positions. A series of such actions can
              jack the piles completely out of the bottom.

                   Possible preventative measures include air bubbler systems and
              pile sleeves, but these must be evaluated on an individual case
              basis.   Relatively comprehensive summaries of current methods. for
              evaluating ice forces on structures are given in Neill (1976),
              Wortley (1978) and the U. S. Army Corps of Engineers (1980b).

                   Vandalism and Theft.    The final factor is the susceptibility
              of the structure to vandalism. If this may be a problem, materials
              should be selected which cannot easily be cut, carried away, dis-
              mantled or otherwise damaged.       For instance, sand-filled fabric
              bags are easily slashed by knives, small concrete blocks can be
              stolen, and wire mesh baskets can be opened with wire cutters and
              the contents scattered.

                                                64

                                 SHORE PROTECTION METHODS

                 This section will examine specific devices, including struc-
            tures and vegetation, in more detail. Where past performance data
            are available, these will be incorporated in the discussion.

            BULKHEADS

                 Because bulkheads normally have vertical faces for ease of
            construction and cost efficiency, wave reflections are maximized,
            increasing the potential for overtopping and scour in front of the
            structure. Since scour can be a serious problem, toe protection is
            necessary for stability.     Typical toe protection consists of
            quarrystone large enough to resist movement by wave forces, with an
            underlying layer of granular material or filter cloth to prevent
            the soil from being washed through voids in the scour apron.

            Sheet Pile Bulkheads

                 Wave Height Range: Above five feet.

                 Sheet piling is available in different materials, including
            steel, aluminum and timber. These are used in structures that may
            be either cantilevers or anchored (Figure 28).      Detailed design
            procedures are available in standard references such as the Steel
            Sheet Piling Design Manual [U. S. Steel Corporation (1975)].

                                                    Fill        Cop
                     Fill,_/_'@ CCap       Original
                                                                     Sheet Pile
                                          ground surface"

                                                                      Wale
                                Sheet Pile

                                                                        //777-
               Originall          -777W07               Tie-Bock
               ground surface
                                              Anchor-
                                             (dead man)

                                                               Li

                                                       ANCHORED

               CANFILEVER

               Figure 28       Cantilever and Anchored Sheet Pile Bulkheads

                                             65

                   A cantilever bulkhead derives its support solely from ground
              penetration; therefore, the sheet piles must be driven deep enough
              to resist overturning.      Cantilever bulkheads are susceptible to
              failure due to toe scour because this reduces the effective embed-
              ment of the piling.

                   An anchored or braced bulkhead gains additional support
              against seaward deflection from embedded anchors or from battered
              structural piles on the seaward side. Anchors are commonly a row
              of piles or deadmen driven or buried a distance behind the bulk-
              head.   Connections between the anchors and wall should be wrought
              iron, galvanized or other suitably corrosion-protected steel.
              Plain carbon steel should not be used for long-term protection.
              Horizontal wales are generally located in the upper one-third of
              the wall height above the dredge line. For low bulkheads, they may
              be at or near the top of the structure. The wales distribute to
              the anchors, the lateral loads on the structure. An anchor system
              is not well suited to sites with buildings close to the shoreline
              because of the distance needed between      the bulkhead and anchors.
              In that case, brace piles may be used in place of anchoring.

                   Subsurface conditions determine the     type of sheet piling that
              can be used.   Steel sheet piling can be    driven into hard soil and
              some soft rock.     Aluminum and timber     sheet piling can only be
              driven or jetted into softer soil.

                   The advantages of sheet pile bulkheads are their relatively
              long and maintenance-free lives, and their uniform appearance.
              Their disadvantages include the special pile-driving equipment
              required to install them.

                   Treated Timber.    Well-designed and built timber structures
              have long been i7e-cognized as viable and economical materials for
              bulkhead construction (Figure 29).        Figure 30 illustrates the
              common types of timber sheeting used. As mentioned earlier, only
              specially treated timber should be used for marine construction. A
              plan view and cross section of a typical timber bulkhead are shown
              on Figure 31.   The actual dimensions will vary. depending on site
              conditions.

                   Granular material is preferred for backfill.       If anchor piles
              are used, backfilling should begin over them, and then proceed to
              the bulkhead. The joints between sheets should be kept as tight as
              possible.   The use of filter fabric is advisable as an added pre-
              caution to prevent loss of soil through cracks. Supplemental drain
              holes should be placed at regular intervals to further facilitate
              the movement of water from behind the structure, and th@se must
              always be backed with filter.cloth or properly graded crushed-stone
              T'Ilters.

                   only corrosion-resistant or protected metals should be used
              for hardware and fasteners. Wrought iron anchor rods with turn-
              buckles and bolts have good durability. Galvanized fasteners are
              also recommended. Carbon steel should not be used unless protected

                                                66

                                                                                   @3"
                     __ ;qo-

                                 Figure     29         Timber     Sheet  Pile   Bulkhead
                                 (Photo    Courtesy of Koppers Company, Inc.)

                                              716* DEEP BY        518.DEEP BY
                                              1 314* WIDE
                                              GROOVE.             1 116' WIDE
                                              EACH SIDE           TONGUE

                                                           0   01

                                                                                            3/4' DEEP BY
                  1 5/6' SQUARE                            E!L@                             1 1/4' WIDE
                    OAK SPLINE_____6-                                I' OFFSET              GROOVE

                                                           0   0                      1    FROM ONE 4*x10'
                                                                                         -OR 4*xl2' ROUGH
                                              FROM ONE
                                              6'x12'                 FROM THREE
                                           -ROUGH                    2'x10' OR
                                              FASTENED  WITH TWO     2'xl2* ROUGH
                                              112* DIAM. DOLTS AND
                                              TWO 30d NAILS AT
                                              18' CENTERS -

                                   SPLINED              WAKEFIELD           TONGUE AND
                                                                               GROOVE

                               Figure 30            Typical Timber Sheet Sections
                                                     [Winterkorn and Fang (1975)]
                                                                        -FS@E@
                                  FI'll                    \   '*'           JE QE
                                                           TH  WO
                                                           'LTS  AND
                                                              T
                                                           .3 A@

                                                               67

                                                                                                  1V

                                                                I" diam. x 18'-2" Tie Rods
                                                                with Turnbuckles
                              E@'x 8" x 10'- 0" Wale            spaced        10'-0"
                                                                                                         Wale 6" x 8" 16'-0'

                                                                                                                    NOTE.'
                                                                   Sheet  Piling T 8 G                              Actual dimensions
                                                                   3"x 12 ' or 3" x 10                              depend on site
                                                                   12' -0" long                                     conditions.

                                 Mean High Water

                                                                                                     'til"-First Stage
                                                                                                           of Filling
                                                                2 /2" Drain Holes
                                                                    20'- 0"
                                                                                            U -6" x 8" x 8' x 6" Tie
                                                                                                 0 10'-0"

                                        Figure 31                      Plan View and Cross Section of
                                                                        Typical Sheet Pile Bulkhead
                                           [American Wood Preservers Institute (1970)]

                     with special coatings, such as coal-tar epoxy or other bituminous
                     materials.               Minimize the number of washers under bolt heads and
                     nuts to reduce the length of exposed bolt shanks, and provide a
                   @tight fit between bolted timbers so that the bolt shanks are not
                     exposed in the gaps. Bolt holes should be no more than 1/16 of an
                     inch larger than the shank to insure a tight fit. Finally, washers
                     should be provided under bolt heads and nuts to insure that these
                     bear evenly on the timber members.

                               Steel.           Steel sheet piling, probably the most widely used
                     bulkhead material (Figure 32), can be driven into hard, dense soilsf
                     and soft rock. The interlocking feature of the sheet pile sections
                     (Figure 33) provides a relatively sand-tight fit that generally
                     precludes the need for filters. This close fit may also be essen-
                     tially water-tight, so regularly spaced weep holes are recommended.

                                                                                      68

                         Figure 32      Steel Sheet Pile Bulkhead

                                BETHLEHEM        FRODINGHAM
                                        Z-SECTIONS

                                         LARSSEN
                                        U-SECTION

                          Figure 33      Steel Sheet Pile Sections
                            [After  Winterkorn and Fang (1975)]

            These, and lifting holes in the piling, should be backed with
            properly graded stone filters or filter fabric to prevent the loss
            of backfill.

                 Aluminum. Aluminum sheet pile sections are similar to steel.
            Design and installation are accomplished using conventional methods
            and equipment.    Its primary advantages over steel are lighter
            weight and superior corrosion resistance. Individual sheets can be
            carried and maneuvered by one man, and most drilling and cutting
            can be performed with simple hand tools.     Its main disadvantage,
            compared to steel, is that it is less rugged when driven and cannot
            penetrate logs, rocks or other hard obstructions. Figure 34 is a
            photograph of an aluminum bulkhead.

                                             69

                                       F
                                        57

                                                   771

                  40'.

                                                                  z7____r

                        -A&L

                        Figure 34      Aluminum  Sheet Pile Bulkhead
                         (Photo Courtesy of Koppers Company, Inc.)

                 Asbestos-Cement. Sheet piling made of this material has been
            tried in several lo ations.   Indications are that it often suffers
            significant and rapid deterioration in a marine environment
            [Watson, Machemehl, and Barnes (1979) ] and should be used with
            caution when long life is desired.

            Post Supported Bulkheads

                 Post supported bulkheads consist of regularly spaced posts,
            usually timber, driven into the ground with an attached facing
            material that forms a retaining wall. The posts,. support compon-
            ents of the bulkhead, resist the exerted earth pressures. As with
            sheet piling, a post supported bulkhead can be - either a cantilever
            or anchored.

                 One advantage is that the posts can sometimes be installed
            using only an auger, and the facing material can then be placed by
            hand. The cost of the bulkhead depends on the required spacing of
            the posts, and the type of soil being augured.

                                             70

                 Hogwire Fencing and Stacked Bags

                 Wave Height Range: Below five feet.

                 Hogwire fencing attached to posts can be used to support sand
            bags stacked on the landward side of the fence (Figure 35) to form
            a relatively inexpensive structure.  The sand bags are vulnerable
            to tearing, however, if after being undercut   by toe scour, they
            slide against the hogwire fencing.

                  Figure 35      Hogwire Fencing and Stacked Bag Bulkhead

                 For best performance, use small-mesh wire with a PVC coating,
            because bare wire fencing tends to cut the bags. Tearing of the
            front row of bags can be prevented by filling them with a sand-
            cement mixture. Burlap bags can be substituted for the more expen-
            sive bags when a sand-cement mixture is used.    The material and
            seams of  all sand-filled bags must be resistant to ultraviolet
            light.

                 Place the bottom bags and fencing in a trench excavated to at
            least the  depth of anticipated toe scour.    Anchor or brace the
            posts, or embed them deeply, allowing for loss of support because
            of toe scour. Provide adequate drainage of the retained embankment
            and place stone at the toe of the bulkhead.

                                            71

                  Treated Timber

                  Wave Height Range: Below five feet.

                  Horizontal, pressure-treated planks can be spiked to the
             landward side of posts which are anchored to deadmen or piles in
             the backfill. The planks must be backed   by filter cloth or graded
             stone to prevent  soil losses through the cracks. Riprap toe pro-
             tection should be provided (Figure 36).

                                     Ur
                                                 1A

                                                    Z41*
                                                         J71@0

                                                        4%

                                                              --A

                           Figure  36      Treated Timber Bulkhead

                  Untreated Logs

                  Wave Height Range: Below five feet.

                  Horizontal, untreated logs can be attached to the landward
             side of posts in areas like the Pacific Northwest where there is an
             abundance of such logs.   The same precautions about adequate toe
             protection and filtering also apply.      However, the large gaps
             between logs make adequate filter design more difficult.       If a
             filter cloth is used, it should follow the log contours so that it
             is not excessively stressed by bridging large gaps. However, it is
             vulnerable to damage or vandalism, which would jeopardize the
             entire structure because of the resulting loss of retained fill.
                                               ,W* @
                                              I'A

                                              72

                  Used Rubber Tires

                  Wave Height Range: Below five feet.

                  Used tires can be strung over two rows of treated posts set in
            a staggered pattern, with the tires abutting each other and         filled
            with gravel (Figure 37). The posts can be tied back to logs         buried
            in the backfill with filter cloth placed behind the tires           before
            backfilling.    Under wave action, the gravel tends to wash         out of
            the tires, and the backfill can then escape. Although used tires
            can generally be obtained free, the      cost of the structure is pro-
            bably comparable to other bulkheads      because of the required close
            post spacing.

                                                      4

                                                M,
                                                    V
                                                            P

                     Figure 37        Used  Rubber  Tire and  Post Bulkhead

                  Railroad Ties and  Steel   H-Piles

                  Wave Height Range: Below five feet.

                  Steel H-piles can be driven at regular intervals and railroad
            ties  placed between the flanges of adjacent piles to form a bulk-
            head  (Figure 38). The toe of the structure should be protected by
            armor stone, and proper filtering and granular backfill are needed
            behind the structure. A 12-inch steel channel, welded to the top
            of the H-piles, serves to aline the piles and retain the railroad
            ties.   The structure has performed well and would be particularly
            useful  where subsurface rock prevents driving sheet piling. How-
            ever,  its cost is probably higher than other effective devices.

                                                73

                                                                    Wail

                                                      %N,

                                                             rob%,

                                                   -ViL IL
                                                 7V,
                                       qh Wa

                     Figure 38       Railroad Ties and Steel  H-Pile Bulkhead

              Miscellaneous Bulkheads

                   Longard Tu es

                   Wave Height Range:   Below five feet.

                   A Longard tube is a  patented, woven, polyethylene tube, filled
              with sand at installation (Figure 39) and available in 40- and
              69-inch diameters, and lengths up to 328 feet.       Like sand-filled
              bags, performance depends on the fabric remaining intact, and the
              tube completely filled. When filled, the tube is dense and heavy,
              yet flexible enough to settle if depressions occur. A properly in-
              stalled Longard tube is placed on a woven filter cloth extending
              10 feet seaward of the tube.        A small 10-inch tube, factory-
              stitched to the seaward edge of the filter cloth, settles under
              wave action to provide toe protection.

                   The primary advantage of a Longard tube is the ease and speed
              with which it can be filled once equipment and materials are in
              place.   Repairs are possible using sewn-on patches.        The . major
              disadvantage is its vulnerability to vandalism and damage by water-
              borne debris.   A sand-epoxy coating can be applied to      dry tubes
              after filling to provide significantly greater protection by deter-
              ring vandals and preventing puncture holes from enlarging.         This
              coating cannot be applied to wet tubes. However, the tube must not
              be allowed to roll after the coating is applied, as uncoated sur-
              face areas would then be exposed, and distortion of the tube may

                                                74

                             Figure 39       Longard Tube Bulkhead

            .cause the existing coating to flake off. other disadvantages are
             that a large supply of good quality sand is required to fill the
             tube, patented filling equipment must be used, and only specially
             licensed contractors can perform the work.

                  The Longard tube depends on its weight to resist overturning
             and on friction to maintain its position.       It is designed to pro-
             tect the toe of the bank from wave attack, and not necessarily to
             resist earth pressures.     The tube should not be placed directly
             against the base of a bank or overtopping waves may continue to
             cause erosion. It should be placed far enough from the toe so that
             overtopping waves will form a sand berm between the tube and the
             bank. Wave energy will be absorbed by this berm, and further bank
             erosion may  be prevented.    Placement of other devices or another
             tube on top, to increase the structure height and prevent overtop-
             ping, is not  recommended.

                  Stacked Used Tires

                  Wave Height Range: Below two feet.

                  Because used tires are readily available at most sites at no
             cost, many have tried to use them for shoreline protection devices.
             The bulkhead on Figure 40 was made with scrap tires interconnected
             (both vertically and horizontally) by galvanized spikes and push-
             nuts. The tires were stacked in a staggered pattern over a filter
             cloth, and granular material was       used both as backfill in low
             areas, and as fill in the tires.       Three rows of galvanized steel
             anchors secured the structure to the beach. The structure progres-
             sively failed because the interconnections between the tires were

                                                75

                                                A

                          Figure 40       Stacked Used  Tire Bulkhead

              inadequate to hold it together.       The gravel washed out of the
              tires, eventually allowing them to   be lifted by waves. This system
              is not recommended in view of better and less costly alternatives.

                   This structure illustrates a common problem with using scrap
              tires. While their availability is a strong temptation to use them
              in shore protection devices, tires are extremely rugged, and usu-
              ally cannot be securely fastened together except by considerable
              labor and expense.    In almost all cases, failure results because
              interconnections do not perform as expected.

                   Used Concrete Pipes

                   Wave Height Range: Below two feet.

                   This bulkhead is constructed by standing used concrete pipes
              on end, side-by-side, and then filling them with granular soil
              (Figure 41).   This bulkhead is economical and practical only when
              there is an available supply of used concrete pipes and where a low
              structure is adequate.

                   A filter must be provided behind the structure to relieve
              hydrostatic pressures.    If a filter cloth is used, it should be
              forced deeply into the grooves between pipes to avoid ballooning
              and bursting the cloth. The wall should not be more than two pipe
              diameters high without an anchoring system. Also, the pipes should
              be entrenched to provide stability and toe protection.         A con-
              tinuous concrete cap (not pictured) could be cast across the tops
              of all pipes to insure performance as a unit. This type of bulk-
              head may not last long because of possible rapid deterioration of
              the concrete pipes.

                                                76

                         Figure 41      Used Concrete Pipe Bulkhead

            REVETMENTS

                 The armor layer of a revetment maintains its position under
            wave action either through the weight or interlocking of the indi-
            vidual units.   Revetments may be classified as flexible, semi-
            rigid, or rigid. Flexible armors, such as quarrystone, riprap, or
            gabions, retain their protective qualities even if the structure is
            severely distorted, such as when the underlying soil settles, or
            scour causes the toe of the revetment to sink. A semi-rigid armor
            layer, such as interlocking concrete blocks, can tolerate minor
            distortion, but the blocks may be displaced if they are moved too
            far to remain locked to the surrounding units. once one unit'is
            completely displaced, such revetments have little reserve strength
            and displacement will generally continue to complete failure.
            Rigid structures may be damaged and fail completely if subjected to
            differential settlement or the'loss of support by underlying soil.
            Grout-filled mattresses of synthetic fabric and reinforced concrete
            slabs are examples of rigid structures.

            Rubble

                 Rubble revetments are constructed of one or more layers of
            stone, or concrete pieces derived from the demolition of sidewalks,
            streets and buildings.   Stone revetments are constructed of either
            two or more layers of uniform-sized pieces (quarrystone), or a
            gradation of sizes between upper or lower limits (riprap). Riprap

                                             77

                revetments are somewhat more difficult to design and inspect be-
                cause of the required close control of allowable gradations and
                their tendency to be less stable under, large waves. For that rea-
                son, graded riprap revetments should be used with caution, but they
                are acceptable for the majority of low cost shore protection appli-
                cations.    Quarrystone structures are more easily designed and in-
                spected and are recommended.

                      The primary advantage of a rubble revetment is its f lexibil-
                ity, which allows it to settle into the underlying soil or experi-
                ence minor damage and still continue to function. Because of its
                rough surface, it also experiences less wave runup and overtopping
                than a smooth-faced structure. The primary disadvantage is that
                placement of the stone or concrete armor material generally re-
                quires heavy equipment.

                      To insure good performance, prepare the existing ground to a
                stable slope.     in most cases, the steepest recommended slope would
                be 1 vertical on 2 horizontal (1:2). Fill material should be added
                where needed   to achieve a uniform slope, but it should be free of
                large stones    and should be firmly compacted before revetment con-
                struction proceeds.      Properly sized filter layers should be pro-
                vided to prevent the loss of the slope material through voids in
                the revetment stone. If using filter cloth, an intermediate layer
                of smaller stone below the armor layer may help distribute the load
                and prevent rupture of the cloth.

                      No individual armor unit should be longer than three times its
                minimum dimension.     In other words, avoid using plate-like or cyl-
                inder-shaped pieces; stones should be angular and blocky, not
                rounded.    The toe of the revetment should be located one design
                wave height (but at least three feet) below the existing grade line
                to prevent undercutting.       In lieu of deep burial, a substantial
                sacrificial berm of additional rubble (with filtering) should be
                provided at the toe.

                      Quarrystone and Riprap

                      Wave Height Range: Above five feet (Quarrystone).

                                            Below five feet (Riprap).

                      Stone revetments are a proven method of shoreline protection
                (Figure 42).    They are durable and can be relatively inexpensive
                where there is a local source of suitable armor stone. Quarried
                stone should be clean, hard, dense, durable, and free of cracks and
                cleavages.    Figure 43 shows a typical cross section of a stone
                revetment. The weight of the armor stones should be determined by
                the following formula as given in the Shore Protection Manual
                [U. S. Army'Corps of Engineers (1977c)].
                                                         w H  3
                                                          r
                                            W              1)3 cot  0                    (17)
                                                 KD (Sr

                                                    78

                                     AIL

                                                                           W'd

                               ELMO&.,,-

                            Figure 42       Quarrystone Revetment

            where W =  weight of an individual armor stone (pounds);
                  wr=  unit3weight (saturated surface dry) of the rock (lbs/
                       feet

                  H =  wave height (feet);
                  S =  specific/grav4ty of the armor stone    (wr/w );  where3 w
                  r    64.0 lbs feet   for salt water and 62.4 'Us/feet        Yor
                       fresh water;

              cot 0 =  Slope of the structure expressed as horizontal units/l
                       vertical;
                  KD=  Stability coefficient from Table 12.

                                          Table 12

                         Stability Coefficients for Stone Revetments
                               Armor Unit                  KD

                            Quarrystone

                              Smooth rounded               2.1
                                      ngul
                              Rough a    ar                3.5

                            Graded riprap                  2.2

                                              79

                                FIRST UNDERLAYER (STONE WEIGHT=W/10)

                                        ARMOR (2 LAYERS)
                                        (STONE WEIGHT =W)

                                                             NOTE.' Use either stone or
                                                                  filter fobric(Both are
                                                                  shown to illustrate
                                                                  their use -only one is
                                                                   needed)

                GRADED STONE                                                     MLW
                FILTER (IF USED IN
                PLACE OF FILTER FABRIC)

                                                                        TOE PROTECTION-
                                                                        BURY AT LEAST
                                                                        THREE FEET OR
                                                                        ONE DESIGN WAVE
                                    FILTER FABRIC (IF                j  HEIGHT BELOW THE
                                    (IF USED IN PLACE OF                BOTTOM
                                    GRADED STONE FILTER

                           Figure 43        Typical Quarrystone Revetment

                    Tables 13, 14, and 15 contain solutions for Equation 17 with
               an illustrative example of their use.

                    If uniform guarrystone is used, the individual stones should
               range from 0.75W to 1.25W with 75 percent of the stones weighing W
               or more.    For graded riprap, W corresponds to W        50      and the
               recommended gradation is 3.6 W    5.0 to 0 -22 W      RlpraVlrhhould be
               limited to areas where the de!.@_3:gn wave hei'gCn)t' is less than five
               feet.

                    If a graded stone filter is employed, it may be significantly
               more fine-grained than the armor layer. This may require the use
               of an intermediate layer of stone between the armor and the filter.
               This layer -should consist of units about 1/10 the weight of stone
               in the armor layer.     This intermediate layer is also recommended
               when a filter cloth is employed because it provides bedding and.
               resists tearing or puncturing of the cloth under the heavy armor
               stone.

                    Concrete

                    Wave Height Range: Below five feet.

                    A concrete rubble revetment utilizes. a waste product that is
               otherwise difficult to dispose of in an environmentally acceptable
               manner. The concrete should have the durability to resist abrasion
               by water-borne debris and ice pressure.       In addition, all protrud-
               ing reinforcing bars should be burned off prior to placement.
               Numerous concrete rubble revetments have failed in the past, but

                                                  80

                          TABLE 13                         TABLE 14                        TABLE 15
                     ESTIMATED WEIGHT                         CORRECTION                CORRECTION FOR

                      OF ARMOR STONE                          FOR SLOPE                      UNIT WEIGHT

                    WAVE           ESTIMATED SLOPE                CORRECTION             UNIT       CORRECTION
                   HEIGHT             WEIGHT                           FACTOR         WEIGHT           FACTOR
                        H                 W                                              Wr
                      (f 0               0b)           (ft/ft)             K I         0b/ft3)              K 2

                      0.5                    1          1:2                1.0           120                4.3
                      1.0                   10          1:2@               0.8           130                2.8
                      1.5                   20                            -0.7           135                2.4
                                                    0
                                                     'eel: 3  mmmelillOw
                      2.0                   50          1: 3@              0.6           140                2.0
                      2.5                 100   #4      1: 4               0.5           145                1.7
                      3.0 mmmmENSP-1 60**               1: 4@              0.4           150                1.5
                      3.5                 260           1: 5               0.4           155mmmogwo-1.3
                      4.0                 390           1: 5@              0.4           160                1.1
                      4.5                 550           1: 6               0.3           165                1.0
                      5.0                 750                                            170                0.9
                      5.5                1000                                            175                0.8
                      6.0                1300                                            180                0.7
                      6.5                1650                                            185                0.6
                      7.0                2100                                            190                0.6

                     EXAMPLE

                    GIVEN.' The wave height (H) is 3.0 feet and the structure
                               slope is 1 on 3 (1 Vertical on 3 Horizontal) and one
                               cubic loot of rock weighs 155 lbs (wr)

                      FIND:
                               The required weight of armor stone (W) from the
                               tables (Dashed Line)

                                          W = 160 lbs x 0.7 x 1.3 = 145 lbs

                                                                   81

              this has generally been attributable to neglect of f ilter require-
              ments.   Figure 44 shows two cross sections that would probably be
              more sucessful than random dumping on a slope. The upper section
              uses three layers of concrete rubble, shaped so that the longest
              dimension is no greater than three times the shortest, thus in-
              creasing stability and minimizing uplift on the slabs from wave
              forces. The revetment shown on Figure 45 is similar, except only
              one layer of rubble was used.      It subsequently suffered damages,
              but more than one layer of rubble may have improved its perfor-
              mance.   The lower 'section on Figure 44 utilizes shaped-rubble
              stacked on a slope to create a stepped face.

                                3 LAYERS OF
                                CONCRETE RUBBLE

                                                                           MHW

                       FILTER
                       CLOTH
                                                                 N\-EXISTING
                                                                     GROUND LINE

                           FILTER.                                            MHW
                           CLOTH

                                                              EXISTING
                                                              GROUND LINE

                       Figure 44      Concrete Rubble Revetment Sections

              Concrete Blocks

                   Concrete blocks for semi-rigid armor layers are designed with
              various intermeshing or interlocking features, and many of the

                                                82

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

                                                                        77

                                     AVI

                         77

                                     IL

                         Figure 45       Concrete Rubble Revetment

           units are patented (Figure 46).      Blocks have the advantage of a
           neat, uniform appearance. Many units are light enough to be in-
           stalled by hand once the slope has been prepared. The disadvantage
           of concrete blocks is that the interlocking feature between units
           must be maintained.     once one block is lost, other units soon
           dislodge, and complete failure may result. A stable foundation is
           required since settlement of the toe or subgrade can cause dis-
           placement of the units and ultimate failure. Also, some concrete
           block revetments have smooth faces that can lead to significantly
           higher wave runup and overtopping.

                Gobi (Erco) and Jumbo Blocks and Mats

                Wave Height Range: Below five feet (blocks).

                                     Above five feet (mats).

                Gobi blocks are patented units that weight about 13 pounds
           each. Erco blocks are similar but they are offered by a different
           licensed manuf acturer.   Jumbo blocks are large-sized Erco blocks
           that weigh about 105 pounds each.        The units are designed for
           hand-placement on a filter cloth or they are factory-glued to
           carrier strips of filter cloth.      The latter are called Gobimats

                                             83

                                                                      COBBLETOP

                                                                                      15

                                                                                                                                                                   2

                                                                      FILTER FABRIC

                                          JUMBO BLOCK                         GOBI (ERCO)         BLOCK                         SHIPLAP BLOCKS

                                                                     4

                                                                                                                           55/e
                                                                                            2.5'

             00                             MONOSLAB
                                          (TURFBLOCK)                                 NAMI RING
                                                         161-                                                                      LOK-GARD BLOCK

                                                                         8"

                                                               CONTROL BLOCKS
                                                                                                                                                          3.0

                                                                             16"

                                                             8                                                             1.55"R(TYP)
                                                                                                                    3.3"R(TYP)
                                                                                                                     4.5"R(TYP)
                                                     STANDARD CONSTRUCTION BLOCK                                              TERRAFIX BLOCK
                                                                        Figure 46                Revetment         Blocks'
                                                                                  ic@

                                                                                                                                                      R-3

                                                            [After U.S. ArMy Corps of Engineers (1981d)]

           (Etcomats) or Jumbo Ercomats, depending on the size of the units.
           If the blocks are glued to both sides of the carrier strip, back-
           to-back, they are called double Gobimats (Ercomats) or double Jumbo
           Ercomats. Mats are preferred at sites where vandalism or theft is
           possibile. Both single and double mats require machine placement.

                Block and mat revetments have generally performed well.         A
           large project on the Gulf of Mexico in Louisiana has weathered
           several hurricanes and tropical storms with only moderate damage to
           the block sections and little or no damage to the mat        portions.
           Figure 47 is a photograph of an existing revetment.

                                            41     vll@

                                                            7777,"

                             Figure 47       Ercomat Revetment

                Turfblocks or Monoslabs.

                Wave Height Range: Below five feet.

                Turfblocks are designed for hand placement on a f ilter with
           the long axis parallel to the shoreline (Figure 48).       Each block
           measures 16 x 24 x 4.5 inches and weighs approximately 100 pounds.
           Field installations have not yielded conclusive results, but their
           performance should be similar to Jumbo Erco blocks.       Their thin,
           flat shape requires a stable foundation, as any differential set-
           tlement beneath the blocks makes them susceptible to overturning
           under wave action.

                                             85

                              law",

                              lw@

                                   W"M             pad
                                             000.

                             AO* AMW
                                 44%,
                                4A __                           I t -., -*__
                                           *"I'-                     *rft@
                                                      @@Zl Pba           0   t n
                                                                t

                              Figure 48      Turfblock Revetment

                  Nami Rings

                  Wave Height Range: Below five feet.

                  The Nami Ring is a patented concrete block shaped like a short
             section of concrete pipe, 2.5 feet in diameter by 1-foot high, and
             weighing 240 pounds.    The rings are placed, side-by-side, on a
             slope over filter cloth. Better performance has been observed when
             the rings are joined together with tie rods. Sand or gravel caught
             up in the wave turbulence tends to be deposited inside the rings
             and in the'voids between adjacent rings, adding to the stability-of
             the section and protecting the filter cloth.      Because of their
             shape, Nami Rings are susceptible to severe abrasion and damage by
             water-borne cobbles and, therefore, should be used primarily in
             sandy environments.

                                              86

                  Control Blocks

                  Wave Height Range: Above five feet.

                  Control blocks come in various sizes and are similar to stand-
            ard concrete construction blocks, except that protrusions in the
            block ends provide a tongue- and-groove interlock between units.
            Designed to be hand-placed on a filter cloth with the cells ver-
            tical, the blocks can be alined with their long axes parallel to
            shore, but optimum     performance   probably results from placement
            perpendicular to the water's edge    (Figure 49).

                                PIZ

                                                             Figure 49
                                                     Control  Block Revetment
                                      Awe
                            IV
                                                     (Note:   Perpendicular orienta-
                                                     tion of  blocks with the water-
                                                     line   is preferred over the
                                                    parallel orientation shown in
                                                     this photograph.)

                  4
                  K

                  Concrete Masonry Blocks

                  Wave Height Range: Above five feet.

                  Standard construction masonry blocks should be hand-placed on
            a filter cloth with their long axes perpendicular to the shoreline
            and the hollows vertical. Their general availability is a primary
            advantage, but they are highly susceptible to theft. They form a
            deep, tightly fitting section which is stable provided the toe and
            flanks are adequately protected.        Their primary disadvantage is
            that standard concrete for building construction is not suffi-
            ciently durable to provide more than a few years service in a
            marine environment.     Special concrete mixes should be used when
            possible

                                               87

                                   Shiplap Blocks

                                   Wave Height Range: Below five feet.

                                   Shiplap- blocks are formed by joining standard concrete patio
                         blocks with an epoxy adhesive.                                      At 100 pounds or more per unit,
                         they are designed for hand placement on a filter. The same precau-
                         tions about concrete mixes apply here. These blocks are discussed
                         in Hall and Jachowski (1964). 'A photograph                                                  and     cross-section of
                         one revetment are shown on Figures 50 and 51.

                                                                                                                                           ki

                                                                                         E,
                                                                                              4
                                                                                                              "74       M'
                                                                                                                                           A

                                                                                             K

                                                                                 N,A

                                                     Figure 50                     Shiplap Block Revetment

                                                                                                                                      Wood railing

                                                           16                                                                         Concrete sidewalk
                                                                                                                                        3'- d' x 6" thick

                                                                                            Original ground line,
                                    EPOXY
                                    Glued
                                     Joint
                                                                      ts-
                                               C                      Z-
                                             Concrete Block Detoils                                                Woven plastic filter cloth

                                              MLW
                                       -Z@Stone     toe protection--_>                                 6' Layer    to 12 stone

                                     2" x 6" Timber
                                                             Toe cutoff wall would be required
                                                              for a sand beach.

                                              Figure        51              Shiplap Block Revetment Section
                                                     [U.S. Army Corps of Engineers (1977c))

                                                                                          88

                 Lok-Gard Blocks

                 Wave Height Range: Below five feet.

                 Lok-Gard blocks join together using a tongue-and-groove system
            (Figure 52).    The 80-pound,   patented units are designed to be
            hand-placed on a filter with their long axes perpendicular to the
            shoreline.   Since a Lok-Gard revetment has a smooth surface, in-
            creased runup heights must be  considered in the design.

                                                 01

                                               TK>

                                                      ItT

                           Figure 52       Lok-Gard Block Revetment

                 Terrafix Blocks

                 Wave Height Range: Above five feet.

                 Terrafix blocks are patented units that join together with a
            mortise and tenon system, and have two cone-shaped projections
            which fit holes in the bottom of the adjacent block (Figure 46).
            In addition, holes through the center of each block allow for
            stainless steel wire connection of many individual blocks.          The
            uniform interlocking of the 50-pound units creates a neat, clean
            appearance (Figure 53).

                 Stacked Bags or Mats

                 Wave Height Range: Below five feet.

                 Several manufacturers produce bags and mats in various sizes
            and fabrics that are commonly filled with either sand or a lean

                                              89

                                                           Figure 53
                                                    Terrafix Block Revetment

                                                  (Photo Courtesy of Erosion
                                                         Control Products, Inc.)

              mixture of concrete for use in revetments. While no special equip-
              ment is required for sand-filled units, a mixer, and possibly a
              pump, are needed for concrete-filled units. Bags should be filled
              and stacked against a prepared slope with their long axes parallel
              to the shoreline and joints offset as in brick work (Figure 54).
              Grout-filled bags can be further stabilized by steel rods driven
              through the bags.

                   The advantage of a bag revetment is its ease of construction
              and moderate cost.   Sand-filled bags are relatively flexible and
              can be repaired if some of the original bags are dislodged.        In
              addition, stacked bag's are suitable as temporary emergency protec-
              tion measures. Among their disadvantages, they are limited to low
              energy areas, have a relatively short service life compared to
              other revetments, and generally have an unattractive appearance.
              Since concrete-filled structures are rigid, any movement or dis-
              tortion from differential settlement of the subgrade can cause a
              major failure that would be hard'to repair.    Sand-filled bags are
              highly susceptible to damage and possible failure from vandalism,
              impact by water-borne debris and deterioration of material and
              seams by sunlight.    The smooth, rounded contours of bags also

                                              90

                                   I uclw
                                             low*

                          Figule 54      Stacked Bag Revetment

               Fig ure 55     Grout-Filled Mattress (Fabriform) Revetment
                    (Photo Courtesy of Construction Techniques, Inc.)

           present an interlocking problem and they should be kept flatter and
           underfilled for stability.

                Mattresses are designed to be laid flat on a prepared slope,
           joined together, and then filled (Figure 55).    They form a large
           mass of pillow-like concrete sections with regularly spaced filter
           meshes for the passage of water. They should always be installed
           according to the manufacturer's recommendations.

                                           91

                    Bags or mattresses should be placed only on a stable slope.
               While a stacked bag revetment can be placed on a steeper slope than
               a mattress, it should not exceed 1 vertical on 1.5 horizontal. A
               stacked bag revetment should be at least two bags thick, preferably
               with the outside layer concrete-filled and the interior bags sand-
               filled.   When sand is used as filler material, the bag or mat
               fabric, and its seams, must be resistant to ultraviolet light.
               Figure 56 shows a nonstabilized bag after six months of exposure.
               Where vandalism or   water-borne  debris are likely, only     concrete-
               filled units should be  used.

                                                 Al

                                   7,

                                             AF

                                                 AW

               Figure 56       Deterioration of Sand   Bags Under Ultraviolet Light

                    Some  form of toe protection should     be provided, or the toe
               should be buried well below the anticipated scour depth. Also, an
               adequate  filter system, such as a properly installed and sized
               filter cloth, should be installed.

                    some types of bags and mats which have been used in the past
               are described below.

                         Burlap Bags.    Burlap bags are recommended only when
                    filleT @witn concrete because of rapid deterioration in the
                    shoreline environment and the ease with which they can be
                    torn.

                         Sand Pillows.    Sand Pillows are ultraviolet-resistant
                    bags made from a woven acrylic fabric.       They weigh approxi-
                    mately 100 pounds when filled. Because of their resistance to
                    sunlight, they are suitable for sand-filling in some areas.

                                                 92

                      Dura BacLs. Dura Bags are large (4 x 12 x 1. 7 feet), and
                 must be filled in place using a pumped sand-slurry or con-
                 crete. Their large size makes them more resistant to movement
                 under wave attack. Fabricated of ultraviolet-resistant mater-
                 ial, they can be used in installations exposed to sunlight.

                      Fabriform Nylon Mat.    The mat is designed to be filled
                 with a highly fluid, lean-cement mixture. The exterior cloth
                 envelope serves primarily as a form until the grout hardens.
                 Fabriform is a patented product, available in several fabric
                 styles, including some with filter points (weep holes) to
                 provide slope drainage.     Fabriform mats should be installed
                 according to the manufacturer's instructions.

            Miscellaneous

                 Gabions

                 Wave Height Range: Above five feet.

                 Gabions are rectangular baskets or mattresses made of gal-
            vanized, and sometimes PVC-coated, steel wire, in a hexagonal mesh
            (Figure 57).    Subdivided into approximately equal sized cells,
            standard gabion baskets are 3 feet wide, and available in lengths
            of 6, 9 and 12 feet and heights of 1, * 1. 5 and 3 feet. Mattresses
            are either 9 or 12 inches thick. At the job site, the baskets are
            unfolded and assembled by lacing the edges together with steel
            wire. The individual baskets are then wired together and filled
            with 4- to 8-inch diameter stone. The lids are finally closed and
            laced to the    baskets,  forming a large, heavy    mass (Figure 58).

                     &

                                      e4
                                          461@*

                             Figure 57       Unassembled Gabions

                                              93

                                   41

                                                        -, Va",

                               Figure 58      Gabion  Revetment

                  One advantage of a   gabion  structure is that it can be built
             without heavy equipment.    Gabions are flexible and can maintain
             their function even if    the foundation settles.   They can be re-
             paired by opening the baskets, refilling them, and then wiring them
             shut again.

                  The disadvantage of a gabion structure is that the baskets may
             be opened by wave action.       Also, since structural performance
             depends on the continuity of the wire mesh, abrasion and damage to
             the PVC coating can lead to rapid corrosion of the wire and failure
             of the baskets.    For that reason, the baskets should be tightly
             packed to minimize movement of the interior stone and subsequent
             damage to the wire.    Rusted 4nd broken wire baskets also pose a
             safety hazard.   Gabion structures require periodic inspections so
             that repairs are made before serious damage occurs.

                  To insure best performance, use properly sized filler rock.
             Interior liners or sandbags to contain smaller sized material are
             not recommended.   The baskets should be filled tightly to prevent
             movement @of the stone and they should be refilled as necessary to
             maintain tight packing.

                  Gabions should not be used where bombardment by water-borne
             debris or cobbles is present, or where foot traffic across them is
             expected..

                                              94

                  Steel Fuel Barrels

                  Wave Height Range: Below five feet.

                  This type of revetment is limited to remote areas with an
            abundance of used fuel barrels of little salvageable value (Fig-
            ure 59). Due to rapid corrosion of the barrels in warm water, the
            system is only reliable in arctic regions. The barrels should be
            completely filled with coarse granular material to preclude damage
            by floe ice and debris, and the critical seaward barrels should be
            capped with concrete.      Also,  partial burial of the barrels in-
            creases stability.

                       ,low"

                         Figure 59        Steel Fuel Barrel Revetment

                  Concrete Slabs

                  Wave Height Range: Below five feet.

                  Photographs of a typical structure were shown on Figure 20.
            The structure failed for a number of reasons, including improper
            filtering, inadequate toe protection, and lack of flank protection.
            Placed on a flatter slope, and with due regard for proper design
            considerations, this type of structure can provide low cost protec-
            tion when large   slabs are available.

                  Fabric and  Ballast

                  Revetments  using a fabric filter cloth as the slope's armor
            layer, held in    place by some form of ballast, have not been suc-
            cessful and are   not recommended.

                                               95

              BREAKWATERS

                   Breakwaters are either floating or fixed.         Floating break-
              waters function at or near the water's surface and must be firmly
              anchored to prevent displacement. Fixed breakwaters are construct-
              ed on the bottom and may or may not pierce the water's surface.
              When they do not, they are called sills.    Their height and porosity
              determines how effectively they dissipate   wave energy.

                   By trapping sand on their landward     side, breakwaters protect
              the shore while simultaneously enhancing    recreational uses. Unlike
              groins, they are able to trap sand moving   both parallel and perpen-
              dicular 'to shore.    Unfortunately, this   sand-trapping (accreting)
              ability can also cause erosion of downdrift beaches. In most cases
              heavy construction equipment, often barge mounted, is necessary for
              breakwater construction.

              Floating Breakwaters

                   Wave Height Range: Below five feet.

                   Floating breakwaters can be constructed of virtually any
              buoyant material such as rubber tires, logs, timbers, and hollow
              concrete modules.    Floating breakwaters are particularly advan-
              tageous where offshore slopes are steep and fixed breakwaters would
              be expensive because of deep water.      They can also be used where
              the tidal range is large and fixed breakwaters would be subjected
              to widely varying degrees of submergence. Floating breakwaters are
              also excellent for temporary installations, such as where vegeta-
              tion requires protection while becoming established.

                   Floating breakwaters have several disadvantages as well. They
              are effective only against short-period waves (less than five
              seconds), which are those most commonly present in sheltered loca-
              tions where low cost protection is most appropriate.        Also, they
              may regarded as eyesores in some areas, they tend to collect float-
              ing debris, and they may require more maintenance than fixed break-
              waters.

                   Rubber Tires.    Two possible arrangements are shown on Fig-
              ure 60. The upper configuration, known as a Wave-Maze, is patented
              and cannot be used without payment of royalties (See Other Help
              Section).   The bottom configuration was developed by the Goodyear
              Tire and Rubber Company for promotional purposes and may be used
              without royalties. The use of other configurations is limited only
              by the imagination of the designer.

                   The basic elements of design for floating tire breakwaters are
              listed below.

                         Length.   The length parallel to shore should be suf-
                   f
                        'E
                    icie t- to provide the desired protection and will vary with
                   the structure's distance from shore.

                                                96

                                 NCHOR
                                 CHAIN

                                      WAVE-MAZE                                 +
                                       DESIGN

                                                                                 BOLTS

                                    If

                  Ff It

                                    BAY

                                 GOODYEAR
                                  DESIGN

                        Figure 60         Floating Tire Breakwater Modules
                         [After U.S. Army Corps of Engineers (1978b)]

                                                    97

                        Width.  The width should be chosen to yield a satisfac-
                  tory decrease in the transmitted wave height (the wave height
                  behind the structure). No definite criteria would apply, but
                  wave height reductions of 30 percent may be an acceptable
                  starting point for design.       This would reduce the energy
                  reaching the protected shoreline to about 49 percent of that
                  of the incident waves (0.7 x 0.7=0.49).       if later experience
                  shows this to be an unsatisfactory or excessive level of pro-
                  tection, the breakwater can be made wider or narrower by
                  adding or removing modules, or its distance from shore or
                  length can be changed.

                        The design breakwater width is a function of the wave-
                  length at the site. With a known water depth and wave period,
                  the wavelength can be found using either Figure 26, or Equa-
                  tion (3).   Figure 61 gives the wave transmission coefficient,
                  K    as a function of the design wave height. The transmitted
                  W@@e height is determined by multiplying the incident wave
                  height by K     For instance, if the local wavelength, L, is 80
                  feet, and V breakwater width, W         of 40 feet is proposed,
                  W /L is 0.50, and K is 0 90.      I?tLe incident wave height is
                  5@@ feet, the translitted* wave    will be 4.5 feet. This wave
                  will contain 0.9 x 0.9, or 81     percent of the energy of the
                  incident wave.    This may not be a satisfactory level of pro-
                  tection in many cases.

                        Draft.   Increased depth of penetration in the water
                  column increases the effectiveness of floating breakwaters.
                  In general, the draft should be greater than one-half the
                  design wave height. Two-layer structures or the use of truck
                  or tractor tires will achieve greater draft.

                        Flotation.   The air trapped within the top of vertical
                  tires provides sufficient flotation in most cases.       In quiet
                  water, the air is eventually dissolved by the surrounding
                  water and the structure sinks.       wave action, however, re-
                  plenishes the air supply, but care must be taken not to use
                  tires with puncture holes.     More permanent flotation is pos-
                  sible with styrofoam blocks or foam injected into the crowns
                  of the tires.    In salt water, marine growth that is not peri-
                  odically removed will eventually sink the structure.           Sand
                  also collects in the tires and can sink them, but this can be
                  prevented by drilling holes in the bottoms of the tires.         In
                  that case, flotation aids such as styrofoam blocks should be
                  used.

                        Fastening Materials.    Stainless and galvanized steel
                  cable; polypropylene, nylon, Poly-D and Kevlar rope; gal-
                  vanized and raw steel chain; and rubber conveyor belt edging
                  have been used for tying tires together.       Davis (1977) pre-
                  sented the results of tests using all of these, and found that
                  conveyor belt edging was the most satisfactory.        The others
                  failed because of either corrosion, abrasion by the tires,
                  fatigue, or deterioration from other factors.        Steel cables
                  sawing through the tires have caused some, devices to fail.

                                                98

                  1.20

                  1.00                                                                        100

                  0.80                                                                        64

                                                                                                   M
                                                                                                   z
                                                                                                   M
               0 0.60                                                                         36

         @10
               0

               0

                                                                                                   z
               E 0.40                                                                          16

                                                                                                   rn
                                                                                                   0
                  0.20                                                                         4

                                                                                               0
                     0       0.20     OAO      0.60     0.80     1.00     1.20     1.40
                                    Ratio of Breakwater Width to Wavelength'(Wst/L)
                            Figure 61     Transmitted Wave Height Versus structure Width
                                           [Giles and Eckert (1979)]

                  Rubber belt edging, a scrap material derived from the manufac-
                  ture of conveyor belts, is available from several rubber
                  companies and comes in a wide range of widths and thicknesses.
                  For tire breakwater construction, the belting should be at
                  least 2 inches wide and 0.375 inches thick.

                       Anchorage.   Floating tire breakwaters must be securely
                  ancho:Fe-dto prevent displacement. Mooring loads can be deter-
                  mined from Figure 62. Danforth and other embedment anchors,
                  as well as screw anchors and large concrete blocks, have been
                  used with mixed results.    They are probably best suited for
                  seasonal use in a mild wave climate, but they tend to creep
                  over long periods in soft bottoms and are not always desirable
                  for permanent installations. In those cases, driven piles are
                  generally the best means of stable anchorage over long peri-
                 .ods.  Giles and Eckert (1979) provide guidance on anchorage
                  systems.

                       Other Materials. other floating materials can be used in
                  place of scrap rubber tires. Bundles of logs can be chained
                  together or other barriers can be fabricated from treated
                  timber. Modules of lightweight concrete filled with flotation
                  foam have also been successful. The proportioning and design
                  factors presented for rubber tire breakwaters would also apply
                  to these.

             Fixed Breakwaters and Sills

                  An important feature of a fixed breakwater is its height,
             which determines how much wave energy passes over the structure.
             In building a fixed breakwater, some settlement should be antici-
             pated in the structure's design height, the actual amount being a
             function of the soil type, the weight of the structure, and type of
             foundation.

                  Longard Tubes

                  Wave Height Range: Below five feet.

                  The advantages and disadvantages of Longard tube bulkheads
             generally apply to breakwaters. An added disadvantage is that the
             protective epoxy coating cannot be applied to wet tubes so that
             damages are more likely. Therefore, they should not be used where
             the tube may be exposed to vandalism or water-borne debris. Fig-
             ure 63 contains before and after views of a Longard tube slashed by
             vandals, eventually causing it to entirely deflate.

                  The tube should be installed over a layer of synthetic filter-
             cloth with factory-sewn, 10-inch Longard tubes on each edge to
             reduce the potential for failure due to toe or heel scour. Where a
             69-inch tube cannot provide sufficient height, an alternate break-
             water system should be used.

                                              100

                        120

                        100

                        80

                     V

                        60
                     C

                      0040

                        20

                                                                      [Giles and Eckert (1979)]
                          0
                          0                                                       4            5
                                                  Incident Wave Height (ft.)
                             Figure 62       Mooring Loads for Floating Tire Breakwaters

                                                        8 march 1979

                                            00
                                        7

                                                     F15 November 19791

                                                                     A
                                         Figure 63
                   Before and After Views of a Longard Tube Breakwater

                 Sand-Filled Bags

                 Wave Height Range: Below five feet.

                 Sand-filled bag breakwaters are constructed of stacked bags in
            a staggered pattern (Figure 64).   The integrity of the structure

                                            102

                         Figure 64       Sand-Filled  Bag Breakwater
            depends on the individual bags remaining in place and intact. The
            bags and seams must be resistant to ultraviolet light to preclude
            deterioration from prolonged sunlight exposure. They should not be
            used where vandalism is expected or where the structure will be
            exposed to water-borne debris.      Lighter bags (100-pound range),
            like those used for revetments, are displaced when exposed to even
            moderate waves.    Larger units, such as Dura Bags, are recommended
            even through they are more difficult to handle and require filling
            in place.

                 A filter cloth should be placed under the bags to reduce
            settlement in soft bottoms (Figure 65).         During construction,
            bag-to-bag abutment should be insured to minimize wave transmission
            through gaps between bags.

                                                         12-FOOT LONG NYLON SANDBAG

                                      1. 7'                          _?1HW

                     ANCHOR
                     SANDBAG

                         FILTER CLOTH                     10,
                                              201
                                               4

                         :G

                     Figure 65       Sand-Filled Bag Breakwater Section
                       [After U.S. Army Corps of Engineers (1978c)]

                                              103

                   Grout-Filled Bags

                   Wave Height Range: Below five feet.

                   The major advantage of grout-filled bags is that the units
              hold their shape after the fabric deteriorates or is torn. Again,
              use of larger bags is recommended because the smaller ones are
              susceptible to displacement.    In addition, larger units reduce the
              number of bag contact points where openings may develop.

                   The recommendations made for sand-filled bags also apply to
              grout-filled bags, except that vandalism is not a major concern.

                   Gabions

                   Wave Height Range: Below five feet.

                   The same basic design considerations for gabion revetments
              also hold here.    The wire mesh should be PVC-coated, the baskets
              should be tightly packed, and a filter cloth should be used beneath
              the structure to help control settlement. A gabion mat should be
              provided around the structure to protect against scour.           Tight
              packing of the stone is particularly important to avoid large
              distortion of the baskets under wave action.         A typical cross
              section and photograph of a gabion breakwater are shown on Fig-
              ures 66 and 67.

                                            18'_O
                        2'-0         9-0                 7'-Ok'
               wire              -0     3'- 0" 2'-d'
               Mes

                                                      OFFSHORE
                                                        SIDE

                                                                     DESIGN WATER
                                                    Stone            LEVEL
               0

               (.0

                                                  Existing Lake Bottom@@J
                                                  (depth from take bottom to bedrock varies)

                       Figure 66      Typical Gabion Breakwater Section
                        [After U.S. Army Corps of Engineers (1978a)]
                                                    S

                                               104

                                 At

                            Figure 67     Gabion Breakwater

                Z-Wall

                Wave Height Range: Above five feet.

                A Z-Wall is a patented device constructed with reinforced
           concrete panels set on edge in a zigzag fashion (Figure 68). The
           structure is designed  for placement close to the shore on the

                                                    . ...... ...
                           Figure 68      Z-Wall Breakwater

                                          105

              existing bottom without the use of a filter. A single bolt acts as
              a hinge that interconnects adjacent panels and allows for non-uni-
              form settlement, but with limited tolerance; so that Z-Walls are
              sensitive to bottom conditions.     If the tolerable differential
              settlement is exceeded, the panels tend to lean against or pull
              apart from each other, causing the concrete to spall in stressed
              areas. The nuts on the connecting bolts tend to unwind under wave
              agitation, and should be inhibited by the use'of double nuts and
              destruction of the exposed threads behind the nuts. Otherwise, the
              end units may fall away if the nuts unwind completely.

                  The Z-Wall performs best at a site with a firm bottom. The
              six-foot panel height limits its use to relatively shallow water.

                  Surgebreaker

                  wave Height Range: Above five feet.

                  A Surgebreaker is a modular device constructed with patented,
              3,700-pound, precast, reinforced concrete modules (Figure 69) with
              vent holes to release wave pressure buildup. The triangular mod-
              ules are 4 feet high and 7 feet wide -    They are designed to be
              placed side-by-side on the existing bottom with the flatter sloped
              face of the device toward the waves (Figure 70).

                                       V

                                                              4A

                                            4.2,

                             Figure 69      Surgebreaker Modules

                                              106

              iJ"
                                                             '@gzl

                                                                          qe

                   R,

                         Figure 70      Surgebreaker Breakwater

                Sandgrabber

                Wave Height Range: Below five feet.

                A patented configuration of interconnected concrete construc-
           tion blocks (Figure 71), the Sandgrabber is a device that allows

                                                         4,

                               Figure 71      Sandgrabber

                                           107

              for some differential settlement of the blocks by using U-shaped,
              galvanized-steel connecting rods. The hollow blocks allow waves to
              wash sand through, trapping the coarser, water-borne particles
              behind the structure.     The Sandgrabber must be installed by a
              franchised contractor.

                   The current design does not use any form of toe protection,
              nor is the structure placed on a filter. As a result, the struc-
              ture normally settles unevenly and rotates seaward into a scour
              trench.  Because of these movements, the allowable amount of dif-
              ferential settlement is sometimes exceeded and the resulting stress
              of the U-ties against the concrete blocks may crack or break them.
              This can eventually lead to complete collapse of the structure.
              Weak concrete hastens the process, so compressive strength tests
              should be performed on each batch of blocks before construction. A
              precaution when using a Sandgrabber, or any other breakwater, is to
              avoid downdrift erosion damages.       Backfilling with sand should
              prevent any potential problems.

                   Quarrystone

                   Wave Height Range: Above five feet.

                   A stone breakwater is structurally similar to a stone revet-
              ment (Figure 72) and stone sizes should also be selected by using
              Equation (17).   However, the stability coefficient, K   D   should be
              selected from Table 16, rather than Table 12.

                                                                        %V

                                             IrA

                                                      _'T
                                                         AT
                                                                      04

                       r

                             Figure 72       Quarrystone  Breakwater

                                               108

                                           Table 16

                                KD VALUES FOR STONE BREAKWATERS

                                                           Structure
                                        Structure Trunk    Head (End)     Slope
                  Armor        Layers          KD              K D        cot 0

            Quarrystone
              Smooth rounded     2             2.1             1.7      1.5 to 3.0

              Rough angular      2             3.5             2.9      1.5
                                                               2.5      2.0
                                                              12.0     13.0

            Graded riprap              Not Recommended

                 A major advantage of a quarrystone breakwater is that the
            structure does not necessarily fail when differential settlement
            occurs. Through the years, stone has been used for more breakwater
            construction than any other material. It is time-tested and can be
            quite economical if suitable rock is available locally.

                 Timber Piles and Brush

                 Wave Height Range: Below two feet.

                 A brush breakwater is constructed of two parallel rows of
            posts driven into the offshore bottom, connected across the top
            with timber crossties, and filled with brush. Brush should be cut
            longer than the space between the posts and placed parallel to the
            structure alinement.    Not suitable for permanent protection, this
            breakwater can be used for temporary sheltering of young vegeta-
            tion.

                 Used Tires and Timber Piles.

                 Wave Height Range: Below two feet.

                 Timber piles can be driven into the bottom, so that every
            three piles form a triangular pattern, and used automobile tires
            can then be stacked on the piles. Just above the top tires, the
            triangularly grouped piles should be interconnected using 2 x 6-
            inch planks bolted to the piles (Figure 73). The structure, whose
            stability depends on the depth of pile penetration, has proven
            effective against mild wave action.

                                              109

                     Figure 73      Used Tire and Timber Pile Breakwater

             GROINS

                  Important design considerations for groins include their
             height, length, spacing (if there are more than one) and the lit-
             toral transport rate. Their height determines how much sand can
             pass over the structure.   Low groins, which essentially follow a
             foot or two above the natural beach profile, are widely used be-
             cause they stabilize the beach but do not trap excessive amounts of
             sand and thereby cause downdrift damages. The groin length should
             not extend past the breaker zone or else it may force the bypassing
             sand too far offshore and cause downdrift erosion damages.       The
             groin spacing should generally be two or three times the groin
             length.

                  Groins can be built as sheet pile structures that depend on
             ground penetration for support, or as gravity structures that
             resist movement solely because of their weight. In either case, it
             is essential to prevent or adequately plan for bottom scour.     For
             sheet pile structures, scour reduces their amount of embedment and
             makes them vulnerable to tipping.     Rigid gravity structures can
             settle unevenly and be damaged if undermined by scour.

                                             110

           Stacked Bags

                Wave Height Range: Below five feet.

                A stacked bag groin is similar to a stacked bag breakwater
           (Figure 74).   The bags can either be sand- or grout-filled.          As
           with breakwaters, larger bags are recommended because lighter,
           smaller bags are too susceptible to displacement.        The recommen-
           dations for bag breakwaters also apply to groins. The bags in the
           photo were filled between wooden forms to achieve their blocky
           shape, but this was unnecessary. When installed properly, stacked
           bag groins have performed well; however,     they should only be con-
           sidered a short-term  solution when filled  with  sand.

                                                               Oy

                     ZANIMM

                              Figure 74       Stacked Bag Groin

           Gabions

                Wave Height Range: Above five feet.

                The recommendations for gabion revetments generally apply.
           The groin should be underlain with filter cloth to inhibit settle-
           ment, and all baskets should be made from PVC-coated wire mesh.
           Tiers of baskets should be tied together with appropriately sized
           wire to prevent shifting of upper tiers over lower tiers, and tight
           packing is needed to minimize distortion of the baskets and damage
           to the wire. Adequate toe protection is required to prevent set-
           tlement and basket distortion.      Thin gabion mattresses are ideal
           for this purpose.

                Figure 75 shows a gabion groin.

                                             ill

                                  Figure 75      Gabion Groin

              Steel Fuel Barrels

                   Wave Height Range: Below five feet.

                   The use of steel fuel barrels for construction is only econo-
              mical in remote arctic areas where used barrels are readily avail-
              able and they have no other salvage value.      Barrel groins have
              worked well where littoral transport characteristics are suitable
              for shore stabilization with a low groin.    The barrels should be
              completely filled with gravel to protect them from crushing by ice
              floes or from damage due to floating debris. They should also be
              capped with concrete for additional strength, and entrenched to
              prevent undermining by scour on the downdrift side.

              Quarrystone

                   Wave Height Range: Above five feet.

                   Quarrystone, a durable and time-tested material for shore
              protection, should always be considered where locally available.
              Figure 76 contains a typical crbss section and profile of a quarry-
              stone groin. The stone should be sized using Equation (17) and
              values from Table 16.   Figure 77 is a photograph of a quarryston%
              groin.

                                              112

                                                                            Variable

                                                                                                               Water Level Datu
                                                    w.,

                                                                              PROFILE

                                     NOTE: Dimensions and details to be         Vortes
                                            determined by particular
                                            site conditions.

                                                                                                               Armor Stone

                                                                        Core Stone (Quarry Run)

                                                                          CROSS-SECTION

                                   Figure 76                    Quarrystone Groin Section and Profile
                                                                [U.S. Army COrPs of Engineers (1977c)]

                                      a' @ �r

                                                                           A

                                                    Figure 77                    Quarrystone Groin

                                                                                113

              Longard Tubes

                   Wave Height Range: Below five feet.

                   Longard tubes have performed fairly well when remaining intact
              (Figure 78).   Failure has usually resulted from holes or tears in
              the fabric and loss of sand fill. Longard tubes are probably best
              as a short term or emergency measure because of their vulnerability
              to damage. When used as a groin, the Longard tube should be under-
              lain by a  filter cloth with 10-inch tubes factory-stitched to each
              side. The filter cloth helps to prevent     settlement, and  the small
              tubes hold the cloth in place.

                                         . . .. . ......

                                                                      14,

                               Figure  78      Longard Tube Groin

              Sheet Piling

                   Wave Height Range: Above five feet.

                   Sheet pile groins, an old and proven means of shore protec-
              tion, can be constructed of timber, steel, or aluminum sheeting.
              Toe protection or adequate embedment is required to insure the
              structure's stability. The general recommendations given for sheet
              pile bulkheads also apply to groins. Figure 79 contains a section
              and profile, and Figure 80 a photograph of a typical sheet pile
              groin.

                                               114

                                                         Riprop Along Updrift Face of Grain              Steel Cap
                                      Riprop Along Downdriff Face of Groin        A

                                        L. W. 0.
                                                                                                        ..Sand Fill
                                                                                                            wn,

                                                                                               Existing Lake Bottom
                                                                Assumed Clay Line                                             MEMO-

                                                                               -.j
                                                                                  A

                                                                                                    tone Toe Protection

                                                                                                _LWD@
                                                                                                -L-
                                                                                  Fi 11; i

                                                                       Assumed Clay Line

                                                                        Steel Sheet Pilin

                                                                                  SECTION A-A

                                                Figure 79                     Sheet Pile Groin Section
                                                 [U.S. Army Corps of Engineers                                (1977c)]

                                                tj,

                                                 Figure 80                     Timber Sheet Pile Groin
                                                                        Steel Sheet PH, 7g

                                                                                      115

              Timber and Rock

                   Wave Height Range: Below five feet.

                   Many structural forms are possible for timber and rock groins.
              Figure 81 shows a timber crib structure that retains a stone f ill.
              Care must be taken to insure that the rock is larger than the gaps
              between the timbers.   Rock has escaped from the offshore compart-
              ment of the groin in the figure for that reason. Treated timbers
              should be used; and to insure structural stability, they should be
              securely fastened together with long wrought iron or coated steel
              rods, threaded at the ends to accommodate washers and nuts.

                   Alternate arrangements for timber groins are possible.      Two
              rows of round structural piles can be driven or augered deep into
              the beach, with timber planking spiked to the piles. The piles can
              be placed close together with the planking set in the space between
              (Figure 82), or the piles can be more widely separated to form a
              crib-type structure (Figure 83).

                                            Q_

                               Figure 81      Timber Crib Groin

                                              116

                                                f fjAp
                                                                                           Nio

                                                                                           NO

                                                     Figure 82                    Timber Plank              Groin

                                                                                                            -71

                                                     Figure        83              Timber Plank              Groin
                                                        f@, Av

                                                                                   117

               BEACH FILLS

                     Beach fills are constructed by mechanical means such as dredg-
               ing and pumping from offshore deposits, or by overland hauling and
               dumping by trucks. The resulting beach provides some protection to
               the area behind it, while also serving as a valuable recreational
               resource.

                     An excess of fill will have to be placed initially because the
               finer material will be lost from the beach as the waves sort the
               deposit.    The amount of overfill needed to account for these ini-
               tial losses depends on the textural characteristics of the fill and
               the in-place material. These are compared by using measures of the
               mean grain size and sorting of the sand.samples as given by Hobson
               (1977).    Sorting is an indication of the range of particle sizes
               that are present. A well sorted sample contains particles that are
               approximately the same 'size.        A poorlg sorted sample contains a
               gradation of particle sizes.

                     Mean grain sizes and sorting are expressed in phi units.
               These are defined as,
                                           -1092  d (mm)                                  (18)
               where, d          the particle diameter in millimeters.
               Note,     (mm)
                                    1092 d(mm) =  logio d   (mm) /loglo(2).
               Therefore,
                                           -3.32 loglod  (mm)                             (19)
                     Table 17 compares the millimeter and phi size scales.

                                                  Table 17

                                  PHI VERSUS MILLIMETER PARTICLE SIZES
                                        d (mm)

                                         256                   -8
                                           64                  -6
                                           8                   -3
                                           4                   -2
                                           2                   -1
                                           1                    0
                                         0.5                    1
                                        0.25                    2
                                       0.125                    3
                                      0.0625                    4

                                                     118

                   An estimate of the mean particle size is
                                               M = 084 + 016                          (20)
                                                        2

             where 084   and 016  are points on the gradation curve that represent
             the  percentage of the sample that is coarser than the particular
             phi size. Phi sorting can be estimated by
                                               S =084 - 016                           (21)
                                                       2

                   Figure 84 provides a fill factor that specifies the amount of
             fill material needed to produce a given volume of in-place materi-
             al. The axes are defined in terms of the mean particle size of the
             borrow (fill) and native (in-place) material (Mb and Mn),   and the
             sorting of the borrow and native material (Sb  and Sn).    For in-
             stance, if Mb  = 3. 0, Sb = 2.0, M = 3.50 and S = 1.00;  the fill
             factor from figure 84 is 1.2.  Therefore, if a  beach containing

                      Figure 84      Fill Factors for Beach Fills
                                     [After Hobson (1977)]

    							119

               1, 000 cubic yards of sand is desired, it will be necessary to
               initially place about 1, 200 cubic yards of sand from the borrow
               source.

                     Figure 85 illustrates the important design factors to consider
               when constructing a beach fill.          The berm elevation should be
               chosen to decrease the likelihood of overtopping by waves during
               storms.   The berm width is determined by geometry to provide for
               the volume of fill to be placed, or for the shoreline use require-
               ments.   The beach s.lope should be chosen to parallel the existing
               profiles and slopes.       This is based on the assumption that the
               existing beach   is in equilibrium with the wave forces and that the
               new beach will eventually assume a similar shape. The shaping of
               the beach fill    profile can either be done by equipment at the time
               it is placed,     or it can be reshaped by waves.          The final equi-
               librium slope    will depend on the texture of the fill material,
               coarser-grained sand resulting in a steeper beach slope than pre-
               viously existed.

                     If fill is placed over a short length of shoreline, it will
               create a projection that will be subject to increased wave            attack.
               Therefore, it is generally preferable to make the transition to the
               existing shoreline over a longer distance.            This may require a
               cooperative effort involving a number of landowners.             If this is
               impractical, protective structures such as groins may be required
               to retain the fill.
                        BERMt

                         EXISTING
                         BOTTOM                                             -DESIGN WATER
                                                                                  LEVEL

                                                                               LOW WAT E R

                                      INITIAL FILL PLACEMENT

                                  ERODED BOTTOM EQUALS
                                  DEPOSITED VOLUME

                                                                         -;;-,-DESIGN WATER
                                                                                  LEVEL

                       FINAL SLO E                                         -LOW WATER
                                C
                       DEPENDS ON COARSENES
                        OF THE SAND

                                 FILL RESPONSE TO STORM WAVES
                                      Figure 85         Beach Fill

                                                   120

            VEGETATION

                 Vegetation has been used for stabilizing shorelines either as
            a substitute for, or supplement to, structures. Vegetation is an
            inexpensive, and generally easy, approach to providing erosion
            control.   It is not, however, applicable to all situations.          it
            cannot always prevent erosion, nor can it stop the recession of
            bluffs caused by groundwater seepage.      In order to confront these
            types of problems, it is necessary to consider a combination solu-
            tion such as a structural device and vegetation.

                 Vegetation uses are limited by site characteristics such as
            climate, soil properties, wave exposure, and salinity regimes. The
            following discussion will focus on species which may be used for
            marsh, beach, dune and slope plantings.        For each species, the
            applicable geographical region and planting    specifications will be
            described.   Further information on these      and other species not
            mentioned in this report can be obtained from county offices of the
            Soil Conservation Service, state coastal zone management programs,
            or Corps of Engineers districts.

            Marsh Plants

                 Coastal marshes are those herbaceous plant communities which
            are normally inundated or saturated by surface or groundwater.
            They may be narrow fringes along steep shorelines or they may cover
            wide areas in shallow, gently sloping shore regions typically found
            in bays and estuaries (Figure 86).     In saltwater marshes, salinity
            is generally equal to or slightly less than seawater (35 parts per
            thousand salt).    Freshwater marshes experience water level fluc-
            tuations resulting from groundwater table and seasonal climatic
            changes.

                 To establish a coastal marsh, the site must be evaluated based
            on geographic area, tidal elevation and range, salinity, fetch
            length, and soil properties.      The vegetation prevalent in three
            saltwater marsh regions and the Great Lakes are discussed below.
            Planting specifications are summarized in Table 18.        The suita-
            bility of a site for marsh plantings can be evaluated using Fig-
            ure 87.

                 Atlantic Coast Marshes.    Common vegetation found in Atlantic
            coast marshes is describe    riefly below.

                       Smooth Cordgrass (Spartina alternaflora).      This is the
                 dominant marsh grass from Newfoundland to about central
                 Florida.   It is well adapted to soils not exposed to air that
                 range from coarse sands to silty clays. Three distinct height
                 forms are recognized. The tall form is generally found along
                 tidal creeks and drainage channels, the short form grows on
                 flat or gently sloping areas away from channels, and the
                 medium form, when present, is found in transition areas be-
                 tween stands of the short and tall forms.

                                              121

                                                                                      Table 18

                                                                     PLANTING SPECIFICATIONS FOR MARSH PLANTS

                                 Type                 Planting Time    Plant Form Recommended              Spacing              Tidal Range and Plant Location

                     Atlantic Coast Marshes

                     Smooth cordgrass                 March-May        sprigs                    31 apart                       < 4.51 range-plant MLW to MHW
                     (Spartina alternaflora)                           15 week old seedlings     1.51 apart                     > 4.51 range-plant MTL to MHW
                                                                       6 month old seedlings     1.5' apart
                                                                       or plugs
                     Saltmeadow cordgrass             March-May        Sprigs                    31 apart                       MHW to estimated highest tide
                     (Spartina patens)                                 15 week old seedlings

                     Black needle rush                Spring           Seedlings                 As 1-5 percent of cordgrass    Ab ove MHW
                     (Juncus roemerianus)                                                        plantings

                     Common reed                      Spring           Sprigs                    1.5'-3.01 apart                Above MHW
                     (Pbragmites communis)

                     Mangroves                        Late February-   Seedlings                 1.51 apart                     Generally MTL and above
                       Black (Avicennia germinans)    March            Established plants        61-101 apart
                       Red (Rhizophara mangle)
                       White (LaguncUlaria racemosa)

                     Gulf Coast Marshes

                     Gulf cordgrass                   March-May        Sprigs                    1.5'-3.01 apart                MHW and above
                     (Spartina spartinae)                              15 week old seedlings     1.51 apart
                                                                       6 month old seedlings     1.51 apart

                     Saltgrass                        spring           Seedlings                 1.5'-3.01 apart                MHW and above
                     (Distichlis spicata)

                     Pacific Coast Marshes

                     Pacific cordgrass                April            sprigs                    1.5'-3.01 apart                Below MTL
                     (Spartina foliosa)

                     Pickleweed                       spring           sprigs                    0.51-3.01 apart                MHW to estimated highest tide
                     (Salicornia spp.)                                 Seeds                     5-10 seeds/sq ft.

                     Sedge                            April-June       Seedlings                 1.4'-3.01 apart                Above MTL
                     (Carex lyngbyei)

                     Tufted hair grass                April-May        Seedlings                 1.5'-3.01 apart                Above MLHW
                     (Deschampsia caespitosa)

                     Arrowgrass                       April-June       Seedlings                 1.51-3.01 apart                Above MTL
                     (Triglochlin maritima)

                 A

                             Figure 86      Marsh Vegetation

                     Smooth cordgrass can be planted with a better chance of
                success than any other coastal marsh species native to the
                United States. Its ideal salinity range is 10 to 35 parts per
                thousand. Two to four weeks after planting, 30 to 45 lb/ac of
                a fertilizer which contains equal parts of available nitrogen
                and phosphate should be applied.

                     Saltmeadow Cordgrass (Spartina patens).   This species is
                extensive in the irregularly flooded high marsh zone along the
                Atlantic coast.   It is able to withstand extended periods of
                both flooding and drought, growing in spots where the surface
                drainage is poor and water ponds during rainy periods.        it
                cannot, however, tolerate the daily flooding of the intertidal
                zone.   Saltmeadow cordgrass is a valuable stabilizer in the
                zone between smooth cordgrass and the upland grass species.

                     Two to four weeks after planting, 30 to 45 lb/ac of
                fertilizer containing equal parts of nitrogen and phosphate
                should be applied.

                                           123

                                       I* SHORE                                              2., DESCRIPTIVE CATEGORIES                                                                               3*
                                                VARIABLES                                                                    (SCORE AS INDICATIRM )
                                             FETCH -AVERAGE                                  Score: 0 Score: 2 Score: 4 Score: 6 Score: 8 Score: 10
                                       AVERAOI MIANU                                               LIEU             3.1                6.1             9.1               12.1            awmat
                                       � UMFTM (MILES)                                                              11.91              13.81           13.71             (7.6)
                                       � OPEN WATER SEAMED                                                                                                                                THAN
                                                                                                                    to                 to              to                to
                                       KOMCM TO                                                    30                                                                                     1S.0
                                       ME NMI Of 4S                                                11.81
                                                                                                                    6.0
                                                                                                                                       9.0             12.0              IS.0              (9-41
                                       EITKISOWM?EBKKAI
                                                           ____NZE7                                                 13.71              IS.6)           (7.51             19.4)
                                       b.FETCH-LONGEST                                       SCOW 0 ScoEs: 2 Score: 4                            1 Score: 6          Score: 8 Score: 10
                                       MUST DISTANCE                                               LESS             4.1                8.1             12.1              16.1            mmAnn
                                       IS UNETERS (MILES)
                                                                                                   THAN             12.6)              IS.11           (7.61             110.11
                                       OF OPEN RAT" ND"u                                                                                                                                   THAN
                                       KWMUW Is                                                    .4.0             to                 to              to                to               20.0
                                                                                                   (2.5)
                                       ME UWE IM as                                                                                                                                       112.6)
                                                                                                                      .0               12.0            16.0              20.0
                                                      PER
                                       DIM SIDE If      PENDICULAN.                                                 (5.0)              17.51           (10.01            (12.61
                                       c. SHORELINE                                          Score: 0                           Score: 2 -                           Score: 4
                                                GEOMETRY                                                              COVE                      NWWU1T                                HUD"ND
                                                                                                                                                sixwom                                                OR
                                                                                                                                                                                      ST"mm
                                                SENERAL SRAPE Of ME SNOOELINI                                                                                                        S1101miNE

                                                AT ME PONT OF INTEREST

                                                PLUS 211 METERS (no FT

                                                ON EITNIER SIDE                                                     . . . . . . . . . . . . . . . .
                                                                                                                                                                                                      ZN

                                                                                             Score       0
                                       d. SHORE SLOPE                                                                                            I Score: 4
                                             SLIM OF ME PLANTM6 AREA,                                        GRADUAL
                                             I VERTICAL To NORinmik )                                                         LESS                                   STEEP
                                                                           5;;;;;;w                   1 to IS ON                                       MORE THAN 1 to                          is
                                       a.    SEDIMENT                                        Score: 0               Score: 2           1 Score: 4                1 Score: 6       1 Score: 8
                                                   61ARE SITE of S[glMENIS                         SILT a                 FINE              MIEDIUM               COASISE
                                                                                                   CLAY                   SAND         I       SAND                  SAND         I     GRAVEL
                                       f.    BOAT TRAFFIC                                    Score : 0                           Score : 8                           Score: 16
                                             PROXIMITY Of SITE TO 1AVIUIIOj CMAMNELS               NO NAVIGATION                       NAVIGATION CHANNEL                NAVIGATION CHANNEL
                                                                                                   CHANNEL WITHIN
                                             FIR LAASE VESULS                                       I KILOMETER                        WITHIN I KILOMETER                WITHIN 100 METERS
                                             It SOUL RECREATIONAL CUR                              10.6 MILES 1                        10.6 MILES I                             133OPF)
                                       g. WIND                                               Score: 0                            Score : 4                           Score: 8
                                                                                                        SHIELTIENIIED                  DOES NOT FACIE                           FACES 0
                                                ME ORIENTATION Of ME gf[                                                               IN THE DIKCTION OF                THE DIIIIECTION OF
                                                10 RELAIIIIII 11 LOCAL WINDS                               FROM                        PWEVAIUNG WINDS                   MVAIUNG WINDS
                                                                                                           WIND                                 on                                  on
                                                                                                                                  FIIIEQUENT STORM WINDS             LFREQUENT STORE WINDS
                                                                4, CUMULATIVE WAVE CLIMATE SCORE

                                       SCORE                   1 TO 10: USE SPRIGS AT 3-FOOT SPACINGS IN 10-FOOT
                                                                                             (MINIMUM) ZONES.
                                                            11 TO 20:                        USE SPRIGS*OR 15-WEEK SEEDLINGS AT D2-FOOT
                                                                                             SPACINGS IN 10-FOOT (MINIMUM) ZONES.
                                                            21 To 30: USE 5-7 MONTH SEEDLINGS OR PLUGS AT D2--FOOT
                                                                                             SPACINGS IN 20-FOOT (MINIMUM) ZONES.
                                                           ABOVE 30:                         DO NOT PLANT

                                                    Figure 87                                      site Evaluation Form for Marsh Plants
                                                                                        [After U.S. Army Corps of Engineers (1980)]

                                                                                                                          124

                       Black Needle Rush (juncus roemerianus). This species is
                  extensive along the Ttlantic coast south of New England.           It
                  is found in high marshes where it is f looded only by wind-
                  driven tides or in areas near the edge of uplands where fresh-
                  water seepage regularly occurs.        It is a good stabilizer,
                  although difficult to propagate, yet under favorable condi-
                  tions it will invade areas already populated by cordgrasses.

                       Common Reed (Phragmites communis). The common reed grows
                  4.5 to 12 feet    tall and is widely distributed in brackish
                  (salinity range   1 to 35 ppt) to freshwater areas above the
                  mean high water   level.   It is easy to transplant and provides
                  good stability;   however, it does tend to compete with other
                  plants and may   become a nuisance by crowding out more desir-
                  able species.

                       Mangroves.    Three species of mangrove--black (Avicennia
                  germinans), red (Rhizophora mangle), and white (Laguncularia
                  racemosa) --occur along the south Atlantic coast, primarily in
                  Florida.   Mangroves are good stabilizers, but they require
                  considerably more- time (2 or 3 years) than grasses to become
                  established. During this time, - the plants are susceptible to
                  possible damage from tides, traffic, and browsing animals.
                  Mangrove seeds, seedlings, or plants are best planted in
                  established cordgrass stands, which provide stability until
                  the mangroves are established.

                       Slow-release (e.g., Osmocote) or a magnesium-ammonium-
                  phosphate fertilizer can be placed in the planting hole if
                  needed, especially for the larger transplants. Daily watering
                  may be required if flooding does not occur.

                  Gulf Coast Marshes.    The vegetation found in gulf coast mar-
            shes  does not substantially differ from south Atlantic coast mar-
            shes.   Grasses, primarily saltgrass and gulf cordgrass, are preva-
            lent, while smooth cordgrass, saltmeadow cordgrass, and black
            needle rush are also common.

                       Gulf Cordgrass (Spartina spartinae).       Gulf cordgrass is
                  found al-ong the gulf coast from southwest Louisiana to Texas.
                  It performs well above the mean high water level.             It is
                  propagated like saltmeadow, cordgrass, using the same pro-
                  cedure.

                       Saltgrass (Distichlis spicata).       Saltgrass is generally
                  limited to the more saline, high marshes along the gulf coast.
                  The plant is usually found in a mixture with saltmeadow cord-
                  grass or black needle rush, and is rarely the dominant species
                  except in poorly drained areas or in narrow bands. Saltgrass
                  is more difficult to establish than the cordgrasses and usu-
                  ally is allowed to volunteer into cordgrass plantings.

                  Pacific Coast Marshes.      Vegetation   in marshes along the
                  'T'_                                         the Atlantic coast.
            Pacific coast is more diverse than along

                                               125

              Pacific cordgrass is found along the central and southern Cali-
              fornia coasts.   Pickleweed! sedges, arrowgrass, and tufted hair
              grass are common along the northern Pacific coast.

                        Pacific Cordgrass (Spartina follosa).   It is similar to
                   smooth cordgrass, hilt, it takes longer to establish. It domi-
                   nates below the mean tide level of intertidal marshes. Plants
                   and sprigs should be inserted by hand in holes made in soft,
                   fine-textured soils. Fertilizers should contain equal quanti-
                   ties of available nitrogen and phosphate.

                        Pickleweed (Sallcornia spp. ).   From mean high water to
                   extrei'ehigh tide, various species of pickleweed can be used
                   upslope of Pacific cordgrass.    It will spread both by seeds
                   and vegetatively (by rhizomes and tillers), but because it is
                   shallow-rooted, it is probably not as useful for stabilization
                   as Pacific cordgrass. Pickleweed may be easily established by
                   seeding or by transplanted peat-pot seedlings, and in fact, it
                   often invades disturbed surfaces during the first growing
                   season.

                        Sedge (Carex 1Vngbgei).   Sedge marshes are usually found
                   in areas such as river deltas where silty soils exist. They
                   grow above the mean tide level and are not especially salt
                   tolerant. The plant may respond to nitrogen and phosphorous
                   under deficient conditions. It appears to be one of the best
                   marsh plants available in the Pacific Northwest.

                        Tufted Hair Grass (Deschampsia caespitosa).    This plant
                   predominates in high marshes subject to flooding' only by
                   higher high tides.    It is a   good sediment accumulator and
                   stabilizer once established.   It is generally easy to trans-
                   plant and quick to establish. Fertilizers should be applied
                   where nutrient deficiencies are suspected.

                        Arrowgrass (Triglochlin maritima).      This plant will
                   frequently invade and colonize disturbed     marshes, trapping
                   sediments and debris and helping to create a substrate for
                   other plants. Planting should follow the method described for
                   sedges.

                   Great Lakes Marshes. Marshes of the Great Lakes are generally
              limited in extent, and confined primarily to the protected shores
              of bays and inlets of Lakes Huron and Michigan. Establishing fresh
              water marshes may not provide as satisfactory a level of erosion
              prevention as saltwater marshes. ' The landowner interested in
              establishing fresh water marshes should consider the common reed,
              rushes (Scirpus spp. ) 'such as spike rush, bulrush, and great bul-
              rush, and, in some instances, upland grasses such as reed canary
              grass (Phalaris arundinacea).    More specific information may be
              obtained from those sources suggested at the beginning of this
              section.

                                              126

            Beach and Dune Plants

                 The protection of the upland portions of sandy shorelines can
            be accomplished through the creation of barrier dunes and the sta-
            bilization of present dunes.       Vegetation used to initiate the
            building of barrier dunes is specially adapted to the more severe
            environment of the beach area (Figure 88). Barrier dune formation
            can occur naturally, but it is usually slow and in some areas does
            not happen.    Utilization and proper management of the natural
            processes can accelerate the development.

               f

                 AV
                                                           ;YI

                                                                  NO

                                                                              IZ

                                                                               7,

                               Figure 88       Dune Vegetation

                 The beach provides a     generally  harsh environment for plant
            growth.   Plants must tolerate rapid     sand accumulation, flooding,
            salt spray, sandblasts, wind and water erosion, wide temperature
            fluctuations, drought, and low nutrient levels. Plants capable of
            stabilizing coastal dunes do, however, occur in most coastal
            regions where there is sufficient rainfall to support plant growth.
            These regions and several of the most successful species are dis-
            cussed below.

                                              127

                                 Planting specifications for several selected beach grass
                        species are summarized in Table 19.

                                                                                    Table 19

                                                             SELECTED BEACH AND DUNE GRASS PLANTING SPECIFICATIONS

                                                                                                          Species
                                                                                             Beach Grass
                                        Element                         American                Panic              European               Sea Oats

                          Planting Season
                            Late fall to early winter               Yes+                     Yes                Yes                    No
                            Midwinter                               Yes+                     Optimum            Yes                    Optimum
                            Late winter to early spring             Optimum+                 Optimum            Optimum                Yes
                            Early spring to mid-spring              Yes                      Yes                Yes                    No

                          Available Source
                            Transplants
                            Commercial                              Yes                      Yes                Yes                    Yes
                            Wild harvest                            Yes                      Yes                Yes                    Yes

                          Seed
                            Commercial                              No                       No                 No                     No
                            Wild harvest                            Yes                      Yes                Yes                    Yes

                          Planting Density
                            Eroding site                            18-inch centers          18-incb centers    18-inch centers        18-inch centers
                            Noneroding site                         24-inch centers          24-inch centers    24-inch centers        24-inch centers
                            Stems per transplant                    3                        1                  3                      1

                          Fertilization, Fi st Growing Season             o
                            Composition NPK6                        3-1-0                    2-1-1              7-0-0                  2-1-1
                            Rate lbs/acre (annual)                  200                      24                 40                     240
                            Application periods                     March                    April              April                  April
                              (equal applications in                May                      June                                      Julie
                             months indicated)                      July                     August                                    August
                                                                    September

                          Illegal to harvest in some states.
                          +Season not recommended for Great Lakes.
                          "NPK--Nitrogen-Phosphorous-Potassim.
                          o
                          3-1-1 in Great Lakes.               [After U.S. Army Corps of Engineers (1977c)ll

                                 North Atlantic Region. Extending from the Canadian border to
                       the Virginia capes, American beachgrass is the dominant dune sta-
                      bilizing plant in this region; bitter panicum offers promise as a
                       companion plant.

                                          American Beachgrass                         (Ammophila              breviligulata).                       This
                                 species is probably the most widely used for the initial
                                 stabilization of blowing sand because it grows rapidly and can
                                 effectively trap sand by the middle of the first growing
                                 season. Once established, it multiplies quickly. It prefers
                                 cool weather and plants start growing in early spring and
                                 continue through fall under the most favorable conditions.
                                 The grass can be transplanted over a long planting season with
                                 a good chance of survival. American beachgrass is available
                                 commercially or may also be harvested from wild stands.
                                 Seedlings are the preferred method of planting. Starting from
                                 seed is usually uneconomical because seed supplies are un-
                                 reliable and weeds are difficult to control.

                                          American beachgrass should be planted 8 to 10 inches deep
                                 in loose, dry sand. Shallow planting is the most common cause

                                                                                       128

                  of failure, therefore it is better to place the plant too deep
                  than too shallow.       Transplants may be made from October
                  through May with the optimum period being February through
                  April. The seedlings should be one or more healthy, vigorous
                  stems (culms), with one to three seedlings per hill.           First
                  year growth is related to the size of the seedlings (number of
                  stems) planted.     Spacing varies with the characteristics of
                  the site, but a strip of beachgrass 24 to 40 feet wide,
                  planted 18 inches apart, will generally be effective by t         'he
                  last half of the first growing season. A more practical (and
                  less expensive) method for planting would be 4 rows of 18-inch
                  spacings at the approximate center of the proposed dune. This
                  plot should be flanked on both sides, by four rows each of
                  plants spaced 24, 36, and 48 inches.

                       Newly planted stands of American beachgrass will often
                  respond to the application of 90 to 135 pounds of nitrogen and
                  30 to 45 pounds of phosphorous per acre. These fertilizations
                  should be divided into three applications. The first should
                  be applied as new growth emerges, with subsequent applications
                  at 4- to 6-week intervals.

                        Bitter Panicum (Panicum amarum).      This grass is indige-
                  nous along the Atlantic coast from Connecticut southward. It
                  is best used as a companion to American beachgrass, especially
                  in those areas where the beachgrass is subject to severe
                  attack by the disease soft scale.

                        Bitter panicum should generally be planted at the same
                  time and with the same methods as American beachgrass. since
                  it prefers warm weather, it may be wise to wait until April to
                  plant.   Bitter panicum can be transplanted as mature primary
                  stems or as tillers. Primary stems must be used during late
                  winter and spring until tillers become available.               Young
                  tillers, with some roots and rhizomes attached, grow with very
                  little delay and are the preferred method of planting when
                  available. Plants should be placed 8 to 10 inches deep in the
                  soil.   Bitter panicum should be planted as a percentage (10-
                  20%) of the total beachgrass planting and in the same pattern.
                  Pure stands of bitter panicum are not usually successful
                  except in very small spots, such as those where beachgrass has
                  been reduced by insects or disease. Fertilizer applications
                  are similar to those recommended for beachgrass.

                  South Atlantic Region. This region extends from the Virginia
             capes to Key West.    Sea oats is the dominant plant. However, both
             American beachgrass and bitter panicum, when planted in combination
             with sea oats, will successfully establish dunes, especially in the
             northern part of the region.

                        Sea Oats (Uniola paniculata). More persistent than other
                  stabilizing pecies, sea oats does not provide much initial
                  protection.    It grows slowly, is difficult to propagate, and
                  is not widely available commercially.           However, sea oats

                                                129

                  provide excellent protection when established.        To provide
                  initial protection, sea oats should be planted in mixes with
                  American beachgrass and bitter panicum to the Carolinas and
                  with bitter panicum farther south. As the other grasses thin
                  out, sea oats will spread and dominate the dune.

                       Planting is similar to bath American beachgrass and
                  bitter panicum. Plants should be placed 8 to 10 inches deep,
                  because they are slow starters and the depth is required to
                  prevent dessication and blowouts.     Transplanting can be suc-
                  cessful at any time given proper moisture conditions and
                  healthy transplants. -Optimum planting months are January and
                  February, although in more severe climates, February to April
                  are better.   Single stem transplants perform as well as mul-
                  tiple , stem plantings under most conditions.       Two-year-old,
                  nursery-grown plants appear to be the best stock for trans-
                  plants.

                       Since sea oats is generally planted as part of a mixture,
                  it is recommended that one or two rows of sea oats (or every
                  10th to 20th row in extremely large plots) be planted no
                  closer than 24 inches. A moderate application of nitrogen and
                  phosphate similar to that recommended for American beachgrass
                  can be used to speed establishment of new plantings and to
                  maintain growth and vigor in sand-starved areas.

                       Saltmeadow Cordgrass (Spartina patens).      This plant is
                  more commonly used in marsh plantings (see prior d    iiscussion),
                  but it will frequently invade a beach area and create small
                  dunes which will support other vegetation. It is particularly
                  well suited for this use on low, moist sites where periodic
                  saltbuildup occurs.

                       Plants should be set 6 to 8 inches deep to stay in the
                  moist zone. For dune stabilizing plantings,     'the optimum time
                  is late winter and spring; however, saltmeadow cordgrass can
                  be transplanted in the early summer providing sufficient
                  moisture is available.     Vigorous, multi-stemmed transplants
                  from uncrowded nursery stands are recommended. With vigorous
                  plants, adequate nutrients, and favorable moisture, saltmeadow
                  cordgrass can be planted 16 to 24 inches apart in a single
                  species planting. The transplants will usually benefit from a
                  total of 90 to 135 pounds of nitrogen per acre applied over
                  two to three applications during the first year.       Subsequent
                  fertilization should deliver similar amounts of nitrogen in
                  single applications over the following two or three years.

                       Bermuda Grass (Cynodon dactglon). Although this is not a
                  prominent dune species, it can be used very effectively in
                  special situations.    The coastal hybrid is deep rooting and
                  rapidly establishing and can be used to revegetate areas where
                  American beachgrass has been killed by insects or disease.
                  Turf hybrids will, when properly managed, perform well on the
                  dune environment, where they form a more traffic resistant
                  stand than other types of vegetation.

                                              130

                       Sprigs of Bermuda grass, spaced 18 to 24 inches ap          .art,
                  should adequately stabilize the dune once they are estab-
                  lished.   For turf development, a spacing of 12 inches should
                  be used.    Sprigs may be planted from early spring to the
                  beginning of summer where adequate moisture is available.
                  Sprinkling the sprigs during dry spells will help to assure
                  the survival of the plants. Bermuda grass requires more
                  nutrients than other dune grasses.         As soon as new growth
                  begins in the spring, 30 to 45 pounds of nitrogen per acre
                  should be applied every 4 weeks until the end of summer.
                  Traffic resistant turf can be developed by applying 450 to 900
                  lb/ac of 10-10-10 formula fertilizer in the early spring and
                  supplementing that with 45 to 70 pounds of nitrogen per acre
                  every 4 weeks through the summer.

                  Gulf Region.    The region extends from the gulf coast              of
            Florida to the Mexican border. sea oats and bitter panicum are the
            dominant dune stabilizing species. other species include railroad
            vine and saltmeadow cordgrass.       Establishment of sea oats, bitter
            panicum, and saltmeadow cordgrass should follow prior recommenda-
            tions.    Local variations exist, and the landowner should consult
            local agricultural extension agents and others about differences in
            technique and management of plantings of these species.

                       Railroad Vine (Ipomea pes-caprae). This plant is one of
                  the more prominent pioneer species in this region. It is not
                  generally planted because it is somewhat less effective in
                  trapping sand than dune grasses.       It is, however, capable of
                  rapidly spreading over foredunes, and transplants of the vine
                  may be included as part of a grass establishment planting.

                  North Pacific Region.     This region extends from the Canadian
            border to Monterey, California.       European beachgrass and American
            dunegrass are the dominant sand stabilizing plants of the region.
            American beachgrass may also be applicable in the area.

                       European Beachgrass (An2mophila arenarla). This plant is
                  inexpensive and uspX-widely in this region.             Although it
                  effectively traps sand, it forms dense stands with little
                  outward spread, causing the resulting dunes to have steep
                  windward slopes.    Another disadvantage is that it will often
                  exclude native species, making it difficult to establish mixed
                  plantings.

                       Planting should not be done when the temperature exceeds
                  600 F or is below freezing. Moist sand should be within 3 to
                  4 inches of the surface and the minimum planting depth is 12
                  inches.   The optimum conditions of moisture and temperature
                  for planting usually occur during the late fall, winter, and
                  early spring months in this region. Three to five stems per
                  hill are recommended for transplanting since establishment of
                  dense stands is imperative with the wind conditions in this
                  area.   Spacing and planting patterns should be adapted to the
                  site, but generally, an 18- x 18-inch planting with three to
                  five stems per hill is sufficient. A pattern of several rows

                                                131

                  with plants spaced 12 x 12 inches, bordered by several rows
                  each of plants spaced 18 x 18, 24 x 24, and 36 x 36 inches,
                  will build a stable foredune at less expense than a uniformly
                  spaced planting.   When rapid growth begins (early April), 35
                  to 55 pounds of nitrogen per acre should be applied.

                       American Dunegrass (ElVmus mollis). Although this grass
                  is naEl-veto the northwest, it is more difficult and expensive
                  to propagate than either European or American beachgrass. The
                  grass tends to produce low, gently sloping dunes, often pre-
                  ferable to those dunes built by European beachgrass.

                       American dunegrass should be set 12 inches or more deep
                  in moist sand. satisfactory planting occurs primarily in the
                  months when the grass is dormant; late November through Febru-
                  ary in the northern portion of the region, and not at all in
                  the southern extent.    Planting should be limited to tempera-
                  tures below 550 F. Planting several stems per hill would be
                  desired; however, due to the expense, a close spacing of 12
                  inches with one viable stem makes better use of scarce plant-
                  ing stock.   An application of 35 pounds of nitrogen per acre
                  from a soluble source is recommended as new growth starts.

                  South Pacific Region.    This region extends from Monterey,
             California, to the Mexican border. While some of the beach grasses
             discussed above (e.g., European beachgrass) are applicable in the
             .northern portions of this region, the dominant plants are forbs
             such.as the sea fig.

                       Sea Fig (Carpobrotus edulis and C. aequilaterus).        Sea
                  fig is effective as a sand stabilizer but not good as a dune
                  builder.   It is quite easy to establish; cuttings 4 to 6
                  inches long should be placed about 18 to 24 inches apart in
                  moist sand.   An occasional application of nitrogen at a rate
                  of 30 to 35 pounds per acre is recommended to maintain the
                  plants once established.

                  Great Lakes Region.   Dune development is mostly confined to
             the Michigan and Indiana shores of Lake Michigan; however, the
             discussion which follows is applicable to all the shores of the
             Great Lakes. American beachgrass is the dominant species-.- Native
             species, especially prairie sandreed, will often invade naturally.
             Once the dunes have been stabilized'. volunteer or planted species
             of upland vegetation can be established.     Species of grasses sug-
             gested would include reed canary grass, big bluestem, little blue-
             stem, and switchgrass, all native to the area. These grasses may
             be planted from early May to the middle of June at a rate of about
             0.5 pounds of seed per 1,000 square feet. All require full sun and
             may be mowed occasionally. Reed canary grass is especially useful
             in wet spots.

                  Various ground covers may also be planted. The species which
             may be utilized are best suggested by local agricultural experts.

                                              132

            The same holds true for shrubs and trees.       When planting grasses
            and ground covers, application of 12 pounds of 12-18-12 fertilizer
            per 1,000 square feet is recommended.

                 An additional problem which landowners in the Great Lakes
            region have is the stabilization of bluffs. Often, structural
            corrections are required in concert with vegetation.          Once the
            structural stabilization is accomplished, vegetative cover will aid
            in preventing erosion, reducing seepage, and slowing runoff.

                 The type of vegetation which can be established on bluff
            slopes is dependent upon the slope angle.       Slopes steeper than 1
            on 1 generally preclude successful vegetation, 'but slopes flatter
            than 1 on 3 can be planted as a lawn and maintained in the usual
            manner.   Slopes between 1 on 3 and 1 on 1 can be planted with
            grasses which will not be mowed, ground covers, trees and shrubs,
            or combinations of these three. As mentioned before, local exper-
            tise (e.g., agricultural extension agents) can aid the landowner in
            selecting suitable species and in describing the most practical
            methods of establishment and maintenance.

            PERCHED BEACHES

                 Perched beaches are constructed by placing sand fill behind a
            low breakwater or sill. Sills can be constructed of virtually any
            material described earlier for fixed breakwaters. Beach material
            should be chosen in accordance with guidelines previously given for
            beach fills.    Proper filtering should be provided beneath and
            behind the sill to prevent settlement and loss of retained fill.
            In some cases, navigation markers may be required.

            Sheet Piling

                 Sheet pile sills are similar to bulkheads.          Timber sheet
            piling will generally require filter cloth backing of the shoreward
            face to prevent loss of backfill through joints in the sheeting.
            This is not generally a problem with steel or aluminum sheet pil-
            ing.   Sheet pile sills also form an abrupt step to deeper water
            which may be hazardous to bathers, particularly children.

                 The same precautions about adequate embedment and toe protec-
            tion -for bulkheads also apply to sills.

                                              133

              Concrete Boxes

                   Precast, open concrete boxes (for use in drainage structures)
              can be placed side-by-side and filled with sand to form a sill
              (Figure 89).   During placement, the. gaps between adjacent boxes
              must be minimized to prevent excessive wave transmission through
              the structure and to help retain the perched beach. Filter cloth
              backing is required   and toe protection should be provided on the
              offshore side.

                                                     air

                               Figure 89       Concrete Box Sill

                                               134

                        PROPRIETARY DEVICES AND SPECIALTY MATERIALS
                 The devices and many of the materials discussed in this report
            are not generally available or familiar to local suppliers. Table
            20 covers principal manufacturers that are active nationwide.
            Inclusion of manufacturers in this directory does not necessarily
            represent an endorsement or recommendation of their products by the
            government.   In fact, some items listed herein were not recommened
            for specific applications in this report.

                                          Table 20

                        PROPRIETARY DEVICES AND SPECIALTY MATERIALS

            Device or Material                      Manufacturer

            Erco Blocks               Erosion Control Systems, Inc.
            Ercomat                   3349 Ridgelake Drive
                                      Suite 101-B
                                      Metairie, Louisiana 70002
                                      504/834-5650

            Fabric Bags               Advance Construction Specialities, Inc.
              Advance                 P. 0. Box 17212
                                      Memphis, Tennessee 38117
                                      901/362-0980

              Acrylic Sand Pillows    Monsanto Textiles Company
                                      Customer Service Center
                                      P. 0. Box 5564, Station B
                                      Greenville, South Carolina 29606
                                      803/242-6700

              Dura Bags               Erosion Control, Inc.
                                      205 Datura Street
                                      Suite 319
                                      West Palm Beach, Florida 33401
                                      305/655-3651

              Fabriform               Construction Techniques, Inc.
                                      11900 Shaker Boulevard
                                      Cleveland, Ohio    44120
                                      216/623-0679

            Filter Cloth              Advance Construction Specialities, Inc.
                                      P. 0. Box 17212
                                      Memphis, Tennessee 38117
                                      901-362-0980
                                      (Woven and Nonwoven)
                                      darthaqe Mills
                                      124 West 66th Street
                                      Cincinnati, Ohio    45216
                                      513/242-2740
                                      (Woven)

                                              135

                                               Table 20
                                               (continued)

               Device or Material                       Manufacturer

                                           Celanese Fibers Marketing,Company
                                           Department CE0504
                                           1211 Avenue of the Americas
                                           New York, New York 10036
                                           800/223-9811 (exc. New York, Alaska,
                                           Hawaii)
                                           212/764-8224
                                           (Nonwoven)

                                           DuPont Company
                                           Room 38095
                                           Wilmington, Delaware 19898
                                           (Nonwoven)

                                           Menardi-Southern
                                           Division of United States Filter
                                           Soil and Erosion Control Department
                                             Headquarters
                                           3908 Colgate
                                           Houston, Texas 77017
                                           713/643-6513
                                          -(Woven and Nonwoven)

                                           Nicolon Corporation
                                           Erosion Control Products
                                           Suite 1990
                                           Peachtree Corners Plaza
                                           Norcross (Atlanta), Georgia 30071
                                           404/447-6272
                                           800/241-9691
                                           (Woven)

                                           Erosion Control Products, Inc.
                                           Route 5
                                           Box 406
                                           Daphne, Alabama 36526
                                           205/626-3510
                                           (Woven and Nonwoven)

               Gabions                     Maccaferri Gabions, Inc.
                                           P. 0. Box 43A
                                           Williamsport, Maryland 21795
                                           301/223-8700

                                           Terra Aqua Corporation
                                           Division of Bekaert Steel Wire Corporation
                                           P. 0. Box 7546
                                           Reno, Nevada 89510
                                           702/329-6262

                                                 136

                                          Table 20
                                          (continued)

             Device or Material                     Manufacturer

             Gobi Blocks               Nicolon Corporation
             Gobimat                   Erosion Control Products
                                       Suite 1990
                                       Peachtree Corner Plaza
                                       Norcross (Atlanta), Georgia 30071
                                       404/447-6272
                                       800/241-9691

             Jumbo Blocks              Erosion Control Systems, Inc.
             Jumbo Ercomat             3349 Ridgelake Drive
                                       Suite 101-B
                                       Metairie, Louisiana 70002
                                       504/834-5650

             Lok-Gard Blocks           Coastal Research Corporation
                                       1100 Crain Highway, S.W.
                                       Glen Burnie, Maryland 21061
                                       301/761-0584

             Longard Tube              Edward E. Gillen Company
                                       218 West Becher Street
                                       Milwaukee, Wisconsin 53207
                                       414/744-9824

             Nami Ring                 Robert Q. Palmer
                                       5027 Justin Drive, N.W.
                                       Albuquerque, New Mexico 87114

             Sandgrabber               Sandgrabber, Inc.
                                       3105 Old Kawkawlin Road
                                       Bay City, Michigan 48706
                                       517/686-6601

             Surgebreaker              Great Lakes Environmental Marine, Ltd.
                                       39 South LaSalle Street
                                       Chicago, Illinois 60603
                                       312/332-3377

             Terrafix Blocks           Erosion Control Products, Inc.
                                       9151 Fairgrounds Road
                                       West Palm Beach, Florida 33411
                                       305/793-5650

             Turfblock (Monoslab)      Anchor Block Company
                                       P. 0. Box 3360
                                       St. Paul, Minnesota 55165
                                       612/777-8321

                                             137

                                            Table 20
                                            (continued)

               Device or Material                     Manufacturer

               Wave-Maze                Robert L. Stitt
                                        10732 E. Freer Street
                                        Temple City, California

               Z-Wall                   The Fanwall Corporation
                                        670 Old Connecticut Road
                                        Farmingham, Massachusetts 01701
                                        617/879-3350

                                              138

                                 OVERVIEW OF THE DESIGN PROBLEM

             CHARACTERIZATION OF THE SITE

                  The site to be considered is a sheltered location within an
             estuary. The shoreline is a low bluff about nine feet high. At
             mean low water (MLW), it is fronted by a 15-foot-wide beach. The
             stillwater level is at the toe of the bluff at mean high water
             (MHW).   The bluff slope is approximately 1:1, and the soil is
             fine-grained, mostly sand and silt, with a heavy overgrowth of
             brush and other plants (Figure 90). The number of trees standing
             in the water and lying on the beach is evidence of a long-term and
             chronic erosion problem.      The beach itself consists of fine- to
             coarse-grained material, mostly sand, but      with a   significant frac-
             tion of gravel and cobbles. The       offshore  bottom slope is approxi-
             mately 1 on 33.

                               Figure 90       Design Problem   Site

             WATER LEVELS

                  The spring tide range and mean tide level were determined by
             reference to Tide Tables [U.S. Department of Commerce (1976)].
             Local experience indicated that two feet of storm setup was ap-
             propriate.    The site profile and water levels are summarized on
             Figure 91.

                                                139

                                  ,-EXISTING BLUFF

                                                                                                      + 3.60' M LW                      DESIGN SWL
                                                                                                                                 -4
                                                                                                              MLW                       SPRING   TIDE LE
                                     +0.5' LW_                                         - - - - - -      0.00' MLW                       LOW TIDE LEVE           1.
                                                                               EXISTING OFFSHORE SLOPE-)
                                                                                                                   5d

                                                                        FROM LOCAL EXPERIENCE                     FROM TIDE TABLES
                                                                        STORM SURGE z 2,0 FT.                     SPRING TIDE RANGE= 1.70 FT.
                                     (1) BLUFF HEIGHT=9'                                                          MEAN TIDE LEVEL= + 0. 75 FT MLW
                                     (2) BLUFF SLOPE - I on I                                            rho sprinalide ronae is centerdon the meon tide 1"elot 40.75'ML
                                     (3) OFFSHORE SLOPE - Ion 33
                                     (4) MEASURED DEPTH 50' OFFSHORE= 1.5'at MLW                                DESIGN
                                     (5) DEPTH AT SPRING TIDE - 3. C                                            STILLWATER LEVEL                     + 3.60 MLW
                                     (6) STORM SURGE= 2.0'
                                     (7) DESIGN WATER DEPTH -(5)+(6)z3.I',2.O'-5.1'
                                     (8) DESIGN WAVE HE)GHTzDESIGN DEPTH xO.8z5.IxO.8z4.O`                                                          @2.0
                                                                                                              SPRING TIDE LEVEL                        .1.60 M_LW
                                                                                                                MEAN TIDE LEVEL              0.85,     -0.75 MLVJ

                                                                                                         MEAN LOW WATER (MLW)                          0.00

                                  Figure 91                         Profile and Physical Conditions at the Site

                         WAVE CONDITIONS

                                     The fastest-mile windspeed for the site is:

                                               10-year: 65 mph

                                     Fetch lengths at the site were displayed earlier on Figure 17.
                         This is reprodu                            as Figure 92 for the convenience of the reader.
                                     Fetch Line t
                                               Length: 2.80 nm x 1.15 = 3.22 mi
                                                                   2.80 nm x 6080 = 17,025 ft

                                               Average Depth: 7.2 ft at MLW
                                                                                10.8 ft at design stillwater level

                                     Fetch Line

                                               Lenqth: 2.10 nm x 1.15 = 2.41 mi
                                                                   2.10 nm x 6080 = 12,770 ft

                                               Average Depth: 11.6 ft at MLW
                                                                                   15.2 ft at design stillwater level
                                     Using Tables 5 to 9, or Equations (5) and (6), find the design
                                                                                                                                            ,ING "TU@EVE@L@O'
                                                                                                                                              T6@L @EC_20
                                                                                                                                                       V
                                     +0  M L W -

                         wave height and period (10-year return period).

                                                                                                140

                                                                                                                                                                               V
                                                                    FETCH LINE                                                                                                   .4
                                                                                                2
                                                DEPTHS                                   DEPTHS
                                                                                                                                                                                                                6 5
                                             5                      6                    3            10                12                                                     36        7",
                                                                                                                                                                                      :8
                                                                                                                                 .:Mkri
                                             1                      1              12                 10               @0,04        2                                                                    T,
                                                                                                                                                                                        :9       .............
                                             6                      1              18                   6
                                                                                                                                                      2.:
                                             9                                     18                                            PAS                  10                                      R                                                                 SCA
                                                                    3                                                         11                                                                    PA          6
                                                                                                                                                      12 sg
                                                                                                                           )W:, 10                    12                                      2                  4
                                            27                      10             14                                                                                                                  IF                                    I                -
                                                                                                                                                      24'Mk,
                                            12                      5              13                                                                 .12                      12 ".2 5T
                                                                                                                                                      ma,ke,
                                        Avg: 7.2'                   MLW        Avg:        11.6' MLW                                                                           13'' ".4                                                            NAUTICA
                                                                                                                                                      Piles                    4.
                                        Fetch Length:                         Fetch Length:                                                                                    -'.14 .3
                                                2.80 nm                                  2.10 nm                                                                               2'
                                                                                                                                                                               10      10
                                                                                                                                                                               P,te PA
                                                                                                                                                                                         Files PA
                                                3.20 mi                                  2.40 mi                                                                               12i
                                                                                                                                                                                  1    3       14      3:   4

                                                                                                                                                                               2
                                                                                                                                                                                          F,
                                                                                                                                                                               .13
                                                                                                                                                                               .13@            ',2
                                                                                                                                                      1.5                      hV'-
                                                                                                                                                                                              12
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                                                                                                                  14                                                           IL                4
                                                                                                                                                                                                         8
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                                                       990
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                                                                    12"10                                                                             35
                                                  2                                              12
                                                                                                                                                                                                                                2
                                                        2                   10     2

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                                                                    q"11.4                                                        7i                  :17"."-                  SA4"4,,2                                                 12             2

                                                                                                                                                                                                                                                                    2
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                                                                                                                                                                                                                             7
                                                                                                                                                                               4                                       2'                           2
                                                                                                                                                      Z                        WINDMILL
                                                                                                                                                      16 :7:                                                 5
                                                    4                                                                                                                          :31Pi-                                          3 1
                                                                                                                                                      15 jkl                   * ."' 1' 1,
                                                                                                        1                                             15                       Dot
                                                                                                                                                                               7,@
                                                                                                   2                                                  14                       9                                                                             5
                                                                                                                                                                               fs" to
                                                                                                                                                                               4
                                                                                                   ...........                                                                                                                                              3
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                                                                                                                17                                    16                       3
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                                                                                                         a                                                                     Aft'
                                                                                                                                                                                      "17"
                                                     . ............                                                                                                                                                   4
                                                                    5
                                                     4              M6

                                                                            R
                                                                                                                                                      7                                  R                                                           NO         0
                                                                           '2' PA  ..........               19                                        4
                                                                                                                                                                                                                                       Bridge Creek privatel
                                                                                                 :17

                                                                                                                                                                                                                                                         is marked
                                                                    R          _NFI 4sec 15ft 4 M       1  J& A4                                                                                                             I      tained channel
                                                                                         Piles PA 13
                                                                                                                                                                                                                                    beacons I thru 19.
                                                                                                                                                      Ard

                                                                                                                  Figure                              92                       Fetch Lengths at the Site

                    Fetch Line(Dwith F     3.2 mi and WS = 65 mph:

                         Table 6: d = 10 ft; H = 3.0 ft;,T = 4.0 sec,

                         Table 7: d = 15 ft; H = 4.0 ft; T = 4.0 sec

                    Therefore, by interpolating for d      10.8 ft; H =   3.2 ft; and
              T   4.0 sec.
                    Fetch Line Q with F = 2.4 mi and WS     65 mph:

                         Table 7: d     15 ft; H = 3.5 ft; T = 4.0 sec,

                         Table 8: d     20 ft; H = 4.0 ft; T = 4.0 sec

                    Therefore, by interpolating for d         15.2 ft; H      3.5 ft;
              and T = 4.0 sec.
                    Fetch Line(D is more critical for design, therefore, use

                                              H = 3.5 feet,

                                         and T = 4.0 seconds.
                    This value should be checked against the maximum bre@aking wave
              at the site or just offshore.      (Recall that Fetch Line U1. crosses
              a shoal area near Cedar' Point where the depth is ap roximately 3
              feet under the design stillwater level. Fetch Line )i@l         however,
                                                                       . UZ I
              was more critical for design purposes). With the design stillwater
              condition, the depth at the bluff toe, d     s = 3.1 feet (Figure 90).
                    From Figure 18 with,
                                     ds /gT2= (3.1)/32.2 (4.0)2     0.0060,

                              and        m = 0.03

                                     Hb/ds = 0.98
                    therefore,          Hb = 3.1 x 0.98 = 3.0 ft
                    Therefore, for shoreline protection, use a design wave height
              of 3.0 feet, because that is the maximum that can occur at the site
              under design water level conditions. For any offshore structures,
              such as breakwaters or perched beach sills, the maximum breaker
              height should be checked based on the design depth at the toe of
              the structure.

                                                142

            SELECTION OF DEVICES

            Landowner's Criteria

                  1.   No recreational use of the beach for bathing or fishing
                       is anticipated.

                  2.   The owner eventually hopes to extend an existing dock to
                       deeper water for berthing a pleasure boat.

                  3.   No structures are planned at the top of the bluf f that
                       would interfere with any shore protection devices.

                  4.   The shore protection plan should provide about ten years
                       of protection with minimal maintenance requirements.

            Alternatives

            No Action             Inappropriate.   Unacceptable to the landowner.
                                  Current erosion  rates represent a considerable
                                  financial   loss   at prevailing real estate
                                  prices.

            Relocate              Inappropriate.   The land is now undeveloped.
                                  The owner will  build a retirement home with a
                                  large setback   from the shore.    He desires to
                                  stop erosion now.

            Bulkhead              Appropriate. Equipment access to the job site
                                  presents no problems. Steps can be added later
                                  for access to the dock.      Recreational use of
                                  the beach is not a high priority.

            Revetment             Appropriate.   There is sufficient room for a
                                  regraded slope.

            Breakwaters           Inappropriate.   Scour at the bluf f toe would
                                  not be positively prevented.

            Groins                Inappropriate.    There is little sand-sized
                                  material in alongshore transport at the site.

            Beach Fill            Inappropriate.    Fill provides     no    positive
                                  protection against toe scour. No recreational
                                  beach is desired.    The plan must have minimal
                                  maintenance requirements.

            Vegetation            Inappropriate.   Plantings provide no positive
                                  protection to the bluff toe.    Coarse soils are
                                  not suitable for plantings.

                                               143

              Infiltration and     Inappropriate.   Drainage and infiltration are
              Drainage Controls    not problems at this site.

              Slope Flattening     Inappropriate.   Suitable only in combination
                                   with a revetment.     Slope stability is not a
                                   basic problem.

              Perched Beach        Inappropriate.   Could be used in combination
                                   with a toe protection structure for the bluff
                                   (revetment or bulkhead) and vegetation to help
                                   retain the beach fill, but this would conflict
                                   with owner's desire to extend the existing dock
                                   for berthing a pleasure boat. Also, a recrea-
                                   tional beach is not desired.

                                               144

                                      PERMIT REQUIREMENTS

                   Federal, state, and possibly local permits are required for
              construction in, across, under, or on the banks of navigable waters
              of the United States.     Federal permits are coordinated by the
              applicant and the states through division and district offices of
              the U. S. Army Corps of Engineers, and they are issued as a result
              of two laws, Section 10 of the Rivers and Harbors Act of 1899, and
              Section 404 of the Clean Water Act of 1977, as amended. Section 10
              of the 1899 act requires permits for structures and dredging in
              navigable waters of the United States, which are those coastal
              waters subject to tidal action and inland waters used for inter-
              state or foreign commerce.   In tidal areas, this includes all land
              below the mean high water line.

                   On the Great Lakes, permits are required under this section
              for construction lakeward of the highwater mark, the definition of
              which varies from state to state, and may differ from the federal
              definition.  Where doubt exists, an appropriate state agency or
              Corps district office can provide assistance.

                   Section 404 of the Clean Water Act mandates a federal permit
              for discharges of dredged or fill material in waters of the United
              States, which include'navigable waters as under Section 10 permits,
              as well as tributaries and wetlands adjacent to navigable waters of
              the United States.   Jurisdiction extends inland to the headwaters
              of streams at a point where the average flow is five cubic feet per
              second. Wetlands are defined as "those areas that are inundated or
              saturated by surface or ground water at a frequency and duration
              sufficient to support, and that under normal conditions do support,
              a prevalence of vegetation typically adapted for life in saturated
              soil conditions. Wetlands generally include swamps, marshes, bogs
              and similar areas" [U. S. Army Corps of Engineers (1977b)].

                   A standard application form (ENG Form 4345) must be obtained
              from the local Corps district office. The application must include
              a description of the proposed construction, "including necessary
              drawings, sketches or plans; the location, purpose, and intended
              use of the proposed activity; scheduling of the activity; the names
              and addresses of adjoining property owners; the location and dimen-
              sions of adjacent structures; and the approvals required by other
              federal, interstate, state or local agencies for the work, includ-
              ing all approvals received or denials already made" (U. S. Army
              Corps of Engineers (1977b)).

                   Upon receipt of the application, a public notice inviting
              comments on the application is normally issued. The comment period
              is generally 30 days, although it may be longer or shorter, depend-
              ing on the circumstances.    Applications are generally coordinated
              with the appropriate federal, state, and local agencies as well as
              adjacent property owners, sometimes leading to comments that re-
              quire modification of the original proposal. Beyond these possible
              modifications, if the comments received and study conducted by the

                                              145

               Corps reveal no overriding public interest or environmental prob-
               lems, the application is approved and a permit issued. Although
               variations exist, the process normally requires 75 to 90 days for
               routine applications.     Controversial applications can take con-
               siderably longer.

                    The Corps has adopted a number of conditional general permits
               on a regional and nationwide basis to reduce red tape and paper-
               work.   No separate application is required for activities where
               general permits have been issued. Applicants should check with the
               local District Engineer to determine if the proposed work is cov-
               ered by a general permit and what conditions may apply.

                    Additional information pertinent to local areas is available
               through Corps of Engineers' district offices, or certain state and
               local agencies.    Permit applications should be initiated early to
               avoid unnecessary delays later.

                                                146

                                                                           OTHER HELP

                    CORPS OF ENGINEERS OFFICES

                              It is imperative to contact the Corps early to preclude un-
                    necessary delays later in the permit application processing. Corps
                    offices are also possible sources of information on water levels,
                    wave action, and other physical conditions at a site. Mail addres-
                    ses, office locations, and phone numbers for Corps personnel fa-
                    miliar with coastal processes are given in Table 21.
                                                                                   Table 21

                                                                         CORPS OF ENGINEERS OFFICES

                                          Address                                   Phone                            Jurisdiction

                       U. S. Army Engineering Division, New England          617/894-2400 X-554      Atlantic coast from Maine to the Connecticut-
                       424 Trapelo Road                                                              New York Line
                       Waltham, Massachusetts 02154

                       U. S. Army Engineering District, New York             212/264-5174            Atlantic coast of New York and the New
                       26 Federal Plaza                                                              Jersey coast north of Manasquan Inlet
                       New York, New York 10007

                       U. S. Army Engineering District, Philadelphia         215/597-4714            Atlantic coast of New Jersey and Delaware
                       U. S. Custon House                                                            from Manasquan Inlet, south to the Delaware-
                       2nd,:dnd Che:tnut Street                                                      Maryland Line, including Delaware Bay and
                       Phi   elphi , Pennsylvania 19106                                              the C&D Canal

                       U. S. Army Engineering District,  Baltimore           301/962-2545            Atlantic and Chesapeake Bay shorelines of
                       P. 0. Box 1715                                                                Maryland
                       Baltimore, Maryland 21203
                       Office Location: 31 Hopkins Plaza
                       Baltimore, Maryland 21201

                       U. S. Army Engineering District, Norfolk              804/441-3764            Atlantic and Chesapeake Bay shorelines of
                       803 Front Street                                                              Virginia
                       Norfolk, Virginia 23510

                       U. S. Army Engineering District, Wilmington           919/343-4778            Atlantic coast and interior bays and sounds
                       P. 0. Box 1980                                                                of North Carolina
                       Wilmington, North Carolina 28402
                       Office Location: 308 Federal Building
                       Wilmington, North Carolina

                       U. S. Army Engineering District, Charleston           803/724-4248            Atlantic Coast of South Carolina
                       P. 0. Box 919
                       Charleston, South Carolina 29402
                       Office Location: Federal Building
                       334 Meeting Street
                       Charleston, South Carolina 29402

                       U. S Army Engineering District, Savannah              912/944-5502            Atlantic coast of Georgia
                       P* 0. Box 889
                       Savannah, Georgia 31402
                       Office Location: 200 E Saint Julian Street
                       Savannah, Georgia 31402

                       U. S. Army Engineer District, Jacksonville            904/791-2204            Atlantic coast of Florida and Gulf coast of
                       P. 0. Box 4970                                                                Florida to the St. Marks River
                       Jacksonville, Florida 32201
                       Office Location: 400 West Bay Street
                       Jacksonville, Florida 32202

                       U. S. Army Engineering District, Mobile               205/690-3482            Gulf Coast of Florida from the St. Marks
                       P. 0. Box 2288                                                                River west Louisiana-Mississippi line
                       Mobile, Alabama 36628
                       Office Location: 109 St. Joseph Street
                       Mobile, Alabama 36602

                       U. S. Amy Engineering District, New Orleans           504/838-2480            Gulf coast of Louisiana
                       P. 0. Box 60267
                       New Orleans, Louisiana 70160
                       Office Location: Foot of Prytania Street
                       New Orleans, Louisiana 70160

                                                                                    147

                                                                                     Table 21
                                                                                    (Continued)

                                              Address                                  Phone                           Jurisdiction

                           U. S. Army Engineering District, Galveston           713/764-1211 X -314    Gulf coast of Texas
                           P. 0. Box 1229
                           Galveston, Texas 77553
                           Office Location: 110 Essayons Boulevard
                           400 Barracuda Avenue
                           Galveston, Texas 77550

                           U. S. Army Engineering District, Los Angeles         213/688-5400           Pacific coast of California from the Mexican
                           P. 0. Box 2711                                                              border north to Cape San Martin
                           Los Angeles, California 90053
                           Office Location: 300 North Los Angeles Street
                           Los Angeles, California 90012

                           U. S. Army Engineering District, San Francisco       415/556-5370           Pacific coast of California from Cape San
                           211 Main Street                                                             Martin north to the California-Oregon line
                           San Francisco, California 94105                                             including San Francisco Bay

                           U. S. Army Engineering District, Portland            503/221-6477           Pacific coast of Oregon
                           P. 0. Box 2946
                           Portland, Oregon 97208
                           Office Location: Mulnomah Building
                           319 S.W. Pine
                           Portland, Oregon 97204

                           U. S. Army Engineering District, Seattle             206/764-3555           Pacific coast of Washington and Puget
                           P. 0. Box C-3755                                                            Sound
                           Seattle, Washington 98124
                           Office Location: 4735 East Marginal Way    South
                           Seattle, Washington

                           U. S Army Engineering District, Alaska               907/752-3925           Coast of Alaska
                           P. 0. Box 7002
                           Anchorage, Alaska 99510
                           Office Location: Building 21-700
                           Elmendorf Air Force Base, Alaska

                           U. S. Army Engineering Division, Pacific Ocean       808/438-2837           Hawaii and the Pacific Trust Territories
                           Building 230
                           Ft. Shafter, Hawaii 96858

                           U. S. Army Engineering District, Detroit             313/226-6791           U. S. shorelines of Lakes Superior, Huron
                           P. 0. Box 1027                                                              and St. Clair; the Lake Michigan shoreline
                           Detroit, Michigan 48231                                                     except in Illinois and Indiana; Lake Erie
                           Office Location: Patrick V. McNamara Building                               shoreline of Michigan
                           477 Michigan Avenue
                           Detroit, Michigan 48226

                           U. S. Army Engineering District, Chicago             312/353-0789           Lake Michigan shoreline of Illinois and
                           219 S. Dearborn Street                                                      Indiana
                           Chicago, Illinois 60604

                           U. S. Army Engineering District, Buffalo             716/876-5454 X-2230    U. S. shorelines of Lakes Ontario and Erie
                           1776 Niagara Street                                                         except in Michigan
                           Buffalo, New York 14207

                       STATE COASTAL ZONE MANAGEMENT OFFICES

                                State coastal zone management of f ices can also be sources of
                       information and assistance.                                    Table 22 contains                     addresses             and
                      phone numbers of offices for states that operate coastal zone
                      management programs.

                                                                                    148

                                          Table 22

                       STATE COASTAL  ZONE MANAGEMENT PROGRAM OFFICES

                 State                    Office Address and Phone Number

            Alabama                   Coastal Area Board
                                      P. 0. Box 755
                                      Daphne, Alabama 36526
                                      205/626-1880

            Alaska                    Division of Policy Development and
                                       Planning
                                      office of the Governor
                                      Pouch AP
                                      Juneau, Alaska 99801
                                      907/465-3541

            California                California Coastal Commission
                                      631 Howard Street, Fourth Floor
                                      San Francisco, California 94105
                                      415/543-8555

            Connecticut               Director, Coastal Area Management Program
                                      Department of Environmental Protection
                                      71 Capitol Avenue
                                      Hartford, Connecticut 06115
                                      203/566-7404

            Delaware                  Coastal Management Program
                                      office of Management, Budget, and Planning
                                      James Townsend Building
                                      Dover, Delaware 19901
                                      302/736-4271

            Florida                   office of Coastal Zone Management
                                      Department of Environmental Regulation
                                      Twin Towers Office Building
                                      2600 Blair Stone Road
                                      Tallahassee, Florida 32301
                                      904/488-8614

            Georgia                   Coastal Resources Division
                                      Department of Natural Resources
                                      1200 Glynn Avenue
                                      Brunswick, Georgia 31520
                                      912/264-4771
            Hawaii                    Department of Planning and Economic
                                        Development
                                      P. 0. Box 2359
                                      Honolulu, Hawaii 96804
                                      808/548-4609

                                             149

                                            Table 22
                                          (Continued)

                  State                         Office Address and Phone

              Illinois                  Illinois Coastal Zone Management Program
                                        300 North State Street, Room 1010
                                        Chicago, Illinois 60610
                                        312/793-3126

              Indiana                   State Planning Services Agency
                                        143 West Market Street
                                        Indianapolis,-Indiana 46204
                                        317/2@2-1482

              Louisiana                 Coastal Management Section
                                        Department of Natural Resources
                                        P. 0. Box 44396
                                        Baton Rouge, Louisiana 70804
                                        504/342-7898

              Maine                     State Planning Office
                                        Resource Planning Division
                                        189 State Street
                                        Augusta, Maine 04333
                                        207/289-3155
              Maryland                  Department of Natural Resources
                                        Tidewater Administration
                                        Tawes State Office Building
                                        Annapolis, Maryland 21401
                                        301/269-2784

              Massachusetts             Executive Office of Environmental Affairs
                                        100 Cambridge Street
                                        Boston, Massachusetts 02202
                                        617/727-9530

              Michigan                  Department of Natural Resources
                                        Division of Land Use Programs
                                        Stephens T. Mason Building
                                        Lansing, Michigan 48926
                                        517/373-1950

              Minnesota                 State Planning Agency
                                        550 Cedar Street, Room 100
                                        St. Paul, Minnesota 55155
                                        612/296-2633

                                               150

                                            Table 22
                                          (continued)

                  State                         office Address and Phone

            Mississippi                Bureau of Marine Resources
                                       Department of Wildlife conservation
                                       P. 0. Box Drawer 959
                                       Long Beach, Mississippi 39560
                                       601/864-4602

            New Hampshire              office of State Planning
                                       2-1/2 Beacon Street
                                       Concord, New Hampshire 03301
                                       603/271-2155

            New Jersey                 Bureau of Coastal Planning and Development
                                       Department of Environmental Protection
                                       P. 0. Box 1889
                                       Trenton, New Jersey 08625
                                       609/292-9762

            New York                   Coastal Management Unit
                                       Department of State
                                       162 Washington Street
                                       Albany, New York 12231
                                       518/474-8834

            North Carolina             Department of Natural Resources and
                                         Community Development
                                       Box 27687
                                       Raleigh, North Carolina 27611
                                       919/733-2293

            Ohio                       Department of Natural Resources
                                       Division of Water
                                       1930 Belcher Drive, Fountain Square
                                       Columbus, Ohio 43224
                                       614/466-6557

            Oregon                     Land Conservation and Development
                                          commission
                                       1175 Court Street, NE
                                       Salem, Oregon 97310
                                       @503/378-4097

            Pennsylvania               Department   of   Environmental    Resources
                                       Third and Reily Streets
                                       P. 0. Box 1467
                                       Harrisburg, Pennsylvania 17120
                                       717/783-9500

                                              151

                                             Table 22
                                           (continued)

                   State                         office Address and Phone

              Rhode Island              Coastal Resources Management Program
                                        Washington County Government Center
                                        Tower Hill Road
                                        South Kingstown, Rhode Island 02879
                                        401/789-3048

              South Carolina            South Carolina Coastal Council
                                        wildlife and Marine Resources Department
                                        1116 Bankers Trust Tower
                                        Columbia, South Carolina 29201
                                        803/758-8442

              Texas                     Natural Resources Division
                                        Texas Energy and Natural Resources
                                         Advisory Council
                                        E.R.S. Building
                                        200 East 18th Street
                                        Austin, Texas 78701
                                        512/475-0773

              Virginia                  Council on the Environment
                                        Ninth Floor, Ninth Street Office Building
                                        Richmond, Virginia 23219
                                        804/786-4500

              Washington                Department of Ecology
                                        PV-11
                                        State of Washington
                                        Olympia, Washington 98504
                                        206/753-4348

              Wisconsin                 Office of Coastal Management
                                        Department of Administration
                                        General Executive Facility 2
                                        101 South Webster Street
                                        Madison, Wisconsin 53702
                                        608/266-3687

                                               152

            OTHER SOURCES OF INFORMATION

            Hydrographic Charts

                 Hydrographic charts are     available for a small fee for all
            U. S. coastal waters.     These provide information on water depths
            and fetch lengths to determine the exposure of a site to wave
            action.   Identification of the specific chart and important infor-
            mation about the available chart series are contained in the Nau-
            tical Catalogs given  below. ,

                 Catalog No. 1 -  Atlantic and Gulf coasts,
                 Catalog No. 2 -  Pacific coast and Hawaii,
                 Catalog No. 3 -  Alaska,
                 Catalog No. 4 -  Great Lakes.

                 For information  or mail orders write to:

                       Distribution Division, C44
                       National Ocean Survey
                       Riverdale, Maryland 20840
                       301/436-6990

                 Counter sales are also available at that location as well as
            regional offices of the National Ocean Survey at:

                 439 West York Street
                 .Norfolk, Virginia 23510

             and

                 1801 Fairview Avenue East
                 Seattle, Washington 90102

                 Charts can also be obtained from the U. S. Coast Guard at the
            locations given below.

                 3rd District
                 Governors Island
                 New York, New York 10004

                 9th District
                 1240 East 9th Street
                 Cleveland, Ohio 44199

            Water Levels

                 Tide Tables are available for all coastal areas of the United
            States. These contain predictions of high and low tide elevations
            and their time of occurrence for one calendar year at primary tide
            stations.   Values of time and elevation differences from the pri-
            mary station are also given for numerous secondary stations, as are
            the mean, spring or diurnal tidal ranges for all stations. Tide
            Tables are available from the Distribution Division, National Ocean
            �urvey, at the address above.

                                              153

                  Lake levels are also available in summary form through the
             Monthly Bulletin of Lake Levels for the Great Lakes. This contains
             the current level for each of the lakes, a s  Iix-month projection of
             future lake levels, and the historic high and low lake levels. The
             Monthly Bulletin is available, free, from the:

                  Department of the Army
                  Detroit District, Corps of Engineers
                  P. 0. Box 1027
                  Detroit, Michigan 48231

             SUGGESTED READING

                  Numerous booklets, brochures, and reports, many of them free,
             are available for further study in selected topics and subjects
             presented in this report. Most government reports include either
             their NTIS or GPO accession numbers. Use the NTIS number to order
             documents from:

                  National Technical Information Service (NTIS)
                  Attention: Operations Division
                  5285 Port Royal Road
                  Springfield, Virginia   22161
                  703/557-4650

             Use the GPO number to order documents from:

                  Superintendent of Documents
                  U. S. Government Printing office (GPO)
                  North Capitol and H Streets, N.W.
                  Washington, D.C.   20401
                  202/783-3238

                                             154

             Shore and Lake Processes

             Beach Processes and Sedimentation, Komar, P., Prentice-Hall, Engle-
             wood Cliffs, New Jersey, 1976, 464 pp.

             Coastal Processes and Beach Erosion, Caldwell, J. M., R 1-67, U. S.
             Army Coastal Engineering Research Center, January 1967, (NTIS
             #652 025).

             Ebb and Flow: The Tides of Earth, Air and Water, Defant, A., Ann
             Arbor Science Library Series, University of Michigan Press, Ann
             Arbor, Michigan, 1958.                        1

             Land Against the Sea,   Rayner, A. C., editor, MP 4-64, U. S. Army
             Coastal Engineering Research Center, May 1964, (NTIS # 453 227).

             Landslides:   Analysis and Control, Special Report 176, Transpor-
             tation Research Board, National Academy of Sciences, Washington,
             D.C., 1978, 234 pp.

             Mechanics of Coastal Landslides and the Influence of Slope Para-
             meters, Edil, T. B. and Vallejo, L. E., Engineering Geology,
             Vol. 16, 1980, pp. 83-96.

             New Distributions   of Extreme Winds in the United States, Thom,
             H.C.S., Journal,    Structural Division, ASCE, ST 7, July 1968,
             pp. 1787-1801.

             Our New Beach: How It Works, Dade County Beach Erosion Control and
             Hurricane Protection Project, U. S. Army Engineer District, Jack-
             sonville, Jacksonville, Florida, 20 pp. (free).

             A Primer of Basic Concepts of Lakeshore Processes, Duane, D. B.,
             et. al., MP 1-75, U. S. Army Coastal Engineering Research Center,
             January 1975, (NTIS# A008 010).

             Proposed Criteria for Interpreting Stability of Lakeshore Bluffs,
             Edil, T. B. and Haas, B. J., Engineering Geology, Vol. 16, 1980,
             pp. 97-110.

             Shoreline Erosion and Landslides in the Great Lakes, Edil, T. B.
             and Vallejo, L. E., Proceedings of the 9th International Conference
             on Soil Mechanics and Foundation Engineering, 1977, Vol. 2,
             pp. 51-58.

             Shore Processes and Shoreline Development, Johnson, D. W., Wiley-
            .London, 1919, 584 pp.

             Shore Protection Manual (Vols. I, II, and III), U. S. Army Coastal
             Engineering Research Center, 1977, (GPO Stock # 008-022-00113-1).

             Waves and Beaches:   The Dynamics of the Ocean Surface, Bascom, W.,
             Anchor Books, Garden City, New York, 1964.

                                             155

               Shore Protection (General)

               Consumer Investment in Shoreline Protection, Braden, P., Michigan
               Sea Grant Program, 2200 Bonisteel Boulevard, Ann Arbor, Michigan
               48109.

               Harmony With the Lake:     Guide to Bluff Stabilization, Division of
               Water Resources, Illinois Department of Transportation, Room 1010,
               Marina City Office Building, 300 North State Street, Chicago,
               Illinois 60610, (free).

               Help Yourself, North Central Division, U. S. Army Corps of Engi-
               neers, 536 South Clark Street, Chicago, Illinois 60605, (free).

               Low Cost Shore Protection:     Final Report on the Shoreline Erosion
               Control Demonstration Program, Office, Chief of Engineers, U. S.
               Army Corps of Engineers, Washington, D. C., 20314, (1981).

               The Michigan Demonstration Erosion Control Program in 1976, Brater,
               E. F., et al., University of Michigan Coastal Zone Laboratory,
               Michigan Sea Grant Technical Report No. 55, February 1977.

               A Pictorial History of Selected Structures Along the New Jersey
               Coast, Vesper, W. H. and Essick, M. G., MP 5-64, U. S. Army Coastal
               Engineering Research Center, October 1964, (NTIS # 612 764).

               Shore and Beach, American Shore and Beach Preservation Association,
               P. 0. Drawer 2087, Wilmington, North Carolina 28401, (published
               quarterly: $20 annually).

               Shore Ero, sion Control: A  Guide for Waterfront Property Owners in
               the Chesapeake Bay Area, Baltimore District, U.S. Army Corps of
               Engineers, P.O. Box 1715, Baltimore, Maryland 21203, 62 pp.,
               (free).

               Shoreline Erosion Control, Philadelphia District, U. S. Army Corps
               of Engineers, Attention: -NAPEN-P (SECDP), Custom House, Second and
               Chestnut Street, Philadelphia, Pennsylvania 19106 (free).

               Shore Protection Guidelines: National Shoreline Study, Office,
               Chief of Engineers, U. S. Army Corps of Engineers, Washington,
               D. C., August 1971, 59 pp.

               Waves Against the Shore: An Erosion Manual for the Great Lakes
               Region, Lake Michigan Federation, 53 West Jackson Boulevard, Suite
               1710, Chicago, Illinois 60604, January 1978.

               What You May Need to Know About Owning Shore Property, Great Lakes
               Communicator, Volume II, No. 5, February 1981.

                                                 156

              Shore Protection Design

              AWPI Technical Guidelines for Pressure-Treated Wood (1970).
              S2 Bulkheads:  Design and Construction - Part I
              S3 Bulkheads:  Design and Construction - Part II
              S4 Bulkheads:  Design and Construction - Part III
              S5 Bulkheads:  Hardware and Fasteners
              Pl Timber Piling
              American Wood Preservers Institute, 1651 Old Meadow Road, McLean,
              Virginia  22101.

              Building Salt Marshes Along the Coast of the Continental United
              States,  Woodhouse, W. W., SR 4, U. S. Army Coastal Engineering
              Research Center, May 1979, (GPO #008-022-00133-6).

              Concrete Shore Protection, Portland Cement Association, 33 West
              Grand Avenue, Chicago, Illinois, 1955.

              Designing for Bank Erosion Control with Vegetation, Knuston, P. L.,
              R 78-2, U. S. Army Coastal Engineering Research Center, February
              1978, (NTIS #A051 571).

              Designing Retaining Walls, Bulkheads and Seawalls of Treated
              Timber, American Wood Preservers Institute (address given above).

              Determination of Mooring Load and Transmitted Wave Height for a
              Floating Tire Breakwater, Giles, M. L., and Eckert, J. W., U. S.
              Army Coastal Engineering Research Center, CETA 79-4, September
              1977, (NTIS # A077 905).

              Dune Building and Stabilization With Vegetation,              Woodhouse,
              W.W., Jr., SR-3, U.S. Army Coastal Engineering Research Center,
              September 1978, (GPO #008-022-00124-7).

              Evaluation of Potential Use of Vegetation for Erosion Abatement
              Along the Great Lakes, Hall, V. L., and Ludwig, J. D., U. S. Army
              Coastal Engineering Research Center, MP 7-75, June 1975, (NITS
               A014 137).

              Evaluation of Tying Materials for Floating Tire Breakwaters, Davis,
              Albert P. J., University of Rhode Island, Marine Technical Re-
              port 54, April 1977.

              Factors Affecting the Durability of Concrete in Coastal Structures,
              Mather, B., TM 96, U. S. Army, Beach Erosion Board, June 1957,
              (NTIS #158 634).

              Floating Tire Breakwaters, Gifford, C. A., et. al, Marine Advisory
              Program, 6022 McCarthy Hall, University of Florida, Gainesville,
              Florida, September 1977, (SUSF-SG-77-002).

              How to Build a Floating Scrap Tire Breakwater, Kowalski, T.and
              Ross, N., Marine Advisory Service, University of Rhode Island,
              Narragansett Bay Campus, Narragansett, Rhode Island 02882.

                                               157

               Planting Guidelines  for Marsh Development and Bank Stabilization,
               Knuston, P. L., CETA 77-3, U. S. Army Coastal Engineering Research
               Center, August 1977, (NTIS #A046 547).

               A Practical Design Method for Flexible Marine Retaining Walls,
               Kaiser Aluminum and Chemical Sales, Inc., 300 Lakeside Drive,
               Oakland, California 94643.

               Review of Design Elements for Beach'Fill Evaluation, Hobson, R. D.,
               U. S. Army Coastal Engineering Research Center, TP 77-6, June 1977,
               (NTIS # A042 748).

               Revised Wave Runup Curves for Smooth Slopes, Stoa, P. N., U. S.
               Army Coastal Engineering Research Center, CETA 78-2, July 1978,
               (NTIS # A058 407).

               The Role of Vegetation in Shoreline Management, Great Lakes Basin
               Commission, P. 0. Box 999, Ann Arbor, Michigan 48106, .(single cop-
               ies, free).

               Salt Marsh Establishment and Development, Garbisch, E. W., Jr., et
               al., U. S. Army Coastal Engineering Research Center, TM 52, June
               1975, (NTIS # A014 136).

               Simplified Design Methods of Treated Timber Structures for Shore,
               Beach and Marina Construction, Ayers, J. and Stokes, R., U. S. Army
               Coastal Engineering Research Center, MR 76-4, March 1976, (NTIS
                A022 337).

               Steel Sheet Piling Design Manual, U. S. Steel Corporation, 1975,
               (ADUSS 25-3848-05).

               SurveV of Coastal Revetment TVpes, McCartney, B. L., U.- S. Army
               Coastal Engineering Research Center, MR 76-7, May 1976, (NTIS
               # A026 255).

               Vse of Plastic Filters in Coastal Structures, Barrett, R. J., Pro-
               ceedings of the 10th International Conference   on Coastal Engineer-
               ing, Tokyo, September 1966.

               Variations in Groin Design, Berg, D. W. and     Watts, G. M., U. S.
               Army Coastal Engineering Research Center, R 4-67, September 1967,
               (NTIS # 659 172).

               Wave Runup on Rough Slopes, Stoa, P. N., U. S. Army Coastal Engi-
               neering Research Center, CETA 79-1, July 1979, (NTIS # A073 354).

               Woven Plastic Cloth Filters for Stone Seawalls, Dunham, J. W. and
               Barrett, R. J., Journal, Waterways, Harbors and Coastal Engineering
               Division, ASCE, Vol. WWI, February 1974, pp. 13-22.

                                              158

             Permits and Regulations

             Permi t Program:  A Guide for Applicants, EP 1145-2-1, U. S. Army
             Corps of Engineers, Washington, D. C.

             Regulations to Reduce Coastal Erosion, Wisconsin Coastal Zone
             Management Program, State Office of Planning and Energy, GEF I1,
             101 South Webster Street, Madison, Wisconsin 53702, (free).

             RegulatorV Program of the Corps of Engineers, Federal Register,
             Tuesday, 19 June 1977.

             Shore Management Guidelines:    National Shoreline Studg, Office,
             Chief of Engineers, U.S. Army Corps of Engineers, Washington, D.C.,
             August 1971.

                                            159

                                          GLOSSARY

             Accretion - Accumulation of sand or other beach material at a point
             due to natural action of waves, currents and wind. A build-up of
             the beach.

             Alongshore - Parallel to and near the shoreline; same as LONGSHORE.

             Apogean Tides - Decreased tidal ranges that occur each month when
             the moon is farthest from the earth (apogee).

             Backhoe - Excavator similar to a power shovel except that the
             bucket faces the operator and is pulled toward him.

             Bar - Fully or partly submerged mound of sand, gravel, or other
             unconsolidated material built on the bottom in shallow water by
             waves and currents.

             Beach - Zond of sand or gravel extending from the low water line to
             a point landward where either the topography abruptly changes or
             permanent vegetation first appears.

             Beach Fill - Sand or gravel placed on a beach by mechanical meth-
             ods.

             Beach, Perched - See PERCHED BEACH.

             Bluff - High, steep bank at the water's edge.     In common usage, a
             bank composed primarily of soil. See CLIFF.

             Boulders   Large stones with diameters over 10 inches. Larger than
             COBBLES.

             Breaker    A wave as it spills, plunges, or collapses on a shore,
             iia-tural obstruction, or man-made structure.

             Breaker Zone - Area offshore where waves break.

             Breaking Depth - Stillwater depth where waves break.

             Breakwater - Structure alined parallel to shore, sometimes shore-
             connected, that provides protection from waves.

             Bulkhead - Structure that retains or prevents sliding of land or
             protects the land from wave damage.

             Clav - Extremely fine-grained soil with individual particles less
             tRzat 0.00015 inch in diameter.

             Cliff - High steep bank at the water's edge.      In common usage, a
             bank composed primarily of rock. See BLUFF.

                                              161

               Cobbles - Rounded stones with diameters ranging from approximately
               3 to 10 inches.      Cobbles are intermediate between GRAVEL and
               BOULDERS.

               Crest   Upper edge or limit of a shore protection structure.

               Culm   Single stem of grass.

               Current - Flow of water in a given direction.

               Current, Longshore - Current in the breaker zone moving essentially
               parallel to shore and usually caused by waves breaking at an angle
               to shore. Also called alongshore current.

               Deep Water - Area where surface waves are not influenced by the
               bottom.  Generally, a point where the depth is greater than one-
               half the surface wavelength.

               Diffraction- Progressive reduction in wave height when a wave
               spreads into the shadow zone behind a barrier after the wave has
               passed its end.

               Diurnal - Period or cycle lasting approximately one day. A diurnal
               tide has one high and one low in each cycle.

               Downdrift   Direction of alongshore movement of littoral materials.

               Dune - Hill, bank, bluff, ridge, or mound of loose, wind-blown
               i-aterial, usually sand.

               Duration - The length of time the wind blows in nearly the same
               directi'on across a FETCH (generating area).

               Ebb Tide - Part of the tidal cycle between high water and the next
               low. The falling tide.

               Equatorial Tides - Tides that occur semimonthly as the result of
               the moon beinTover the equator.      At these times the tendency of
               the moon to cause an inequality in mixed tides is minimized.

               Equilibrium - State of balance or equality of opposing forces.

               Erosion - Wearing away of land by action of natural forces.

               Fetch - Area where waves are generated by wind which has steady
               a@irection and speed. Sometimes called FETCH LENGTH.

               Fetch Length - Horizontal direction (in the wind direction) over
               which a wind generates waves.       In sheltered waters, often the
               maximum distance that wind can blow across water.

               Filter Cloth - Synthetic textile with openings for water to escape,
               but which prevents passage of soil particles.

                                               162

              Flood Tide - Part of the tidal cycle between low water and the next
              high.      rising tide.

              Glacial Till - Unstratified glacial drift consisting of unsorted
              clay, sand, gravel, and boulders intermingled.

              Gravel   Small, rounded granules of rock with individual diameters
              ranging from 3.0 to 0.18 inches. Gravels are intermediate between
              SAND and COBBLES.

              Groin - Shore protection structure built perpendicular to shore to
              trap sediment and retard shore erosion.

              Groin Field - Series of groins acting together to protect a section
              of beacS_.Also called a groin system.

              Grout - Mixture of portland cement, fine aggregates (usually sand),
              and water.   Usually used to seal openings or fill bags or other
              containers.'

              H-Pile- Straight length of structural steel with an H-shaped cross
              ie`ction designed for driving into the earth.

              High Tide    Maximum elevation reached by each rising tide.       see
              also TIDE.

              High Water   See HIGH TIDE.

              High Water Line - Intersection of the level of MEAN HIGH WATER with
              the shore.   Shorelines on navigation charts are approximations of
              the high water line.

              Hogwire - Short, smooth-wire fencing of the kind normally used to
              enclose a pig sty.

              Impermeable - Not having openings large enough to permit water to
              freely pass.

              International Great Lakes Datum (IGLD) - Common reference datum for
              the Great Lakes area based on mean water level in the St. Lawrence
              River at Father Point, Quebec, and established in 1955.

              Intertidal Zone   Land area alternately inundated and uncovered by
              tides. Usually considered to extend from MEAN LOW WATER to MEAN
              HIGH WATER.

              Lee - Sheltered; part or side facing away from wind or waves.

              Leeward - Direction toward which wind is blowing or waves are
              travelling.

              Littoral Material - Sediments moved in the LITTORAL ZONE by waves
              and currents. Also called littoral drift.

                                             163

              Littoral Transport    Movement of LITTORAL MATERIAL by waves and
              currents.

              Littoral Zone - Indefinite zone extending from the shoreline to
              just beyond the breaker zone.

              Longshore - Parallel to and near the shoreline:      same as ALONG-
              SHORE.

              Longshore Transport Rate - Rate of transport of littoral material
              parallel to shore.    Usually expressed in cubic yards per year.

              Low Tide - Minimum elevation reached by each falling tide.

              Low Water Datum (LWD) - The elevation of each of the Great Lakes to
              which are referenced the depths shown on navigation charts and the
              authorized depths of navigation projects.

              Low Water Line - Intersection of the low tide level with shore.

              Marsh - Area of soft, wet, or periodically inundated land, gener-
              ally treeless, and usually characterized by grasses and other low
              growth.

              Mean Higher High Water (MHHW)   Average height of the daily higher
              high water over a 19-year period.    Only the higher high water of
              each of the high waters of a tidal day is included in the mean.

              Mean High Water (MHW) - Average height of the daily high waters
              over a 19-year period.    For semidiurnal or mixed tides, the two
              high waters of each tidal day are included in the mean.          For
              diurnal tides, the single daily high water is used to compute    the
              mean.

              Mean Lower Low Water (ML@@ - Average height of the daily lower   low
              waters of a 19-year period. Only the lower low water of each pair
              of low waters of a tidal day is included in the mean. Long used as
              the datum for Pacific coast navigation charts, it is now gradually
              being adopted for use across the United States.

              Mean Low Water (MLW) - Average height of the low waters over a
              19-year period.   For semidiurnal and mixed tides, the two low
              waters of each tidal day  are included in the mean.   For a diurnal
              tide, the one low water of each tidal day is used in the mean.
              Mean Low Water has been   used as datum for many navigation charts
              published by the National Ocean Survey, but it is being phased out
              in favor of Mean Lower Low Water for all areas of the United
              States.

              Mean Sea Level - Average height of the sea surface over a 19-year
              period. Not necessarily equal to MEAN TIDE LEVEL.

                                             164

              Mean Tide Level - Plane midway between MEAN HIGH WATER and MEAN LOW
              WATER.  Not necessarily equal to MEAN SEA LEVEL.          Also called
              half-tide level.

              Mixed Tide - A tide in which there is a distinct difference in
              height      een successive high and successive low waters.          For
              mixed tides there are generally two high and two low waters each
              tidal day.   Mixed tides may be described as intermediate between
              semidiurnal and diurnal tides.

              Module - A  structural component, a number of which are joined to
              make a whole.

              National Geodetic Vertical Datum (NGVD) - Datum of the United
              States geodetic level net.     Mean Sea Level varies slightly from
              this datum from place to place along the shores of the nation.

              Neap Tides - Tides with decreased ranges that occur when the moon
              is at first or last quarter, and the pull of the. sun and moon are
              in opposition to each other.     The neap range is smaller than the
              mean range for semidiurnal and mixed tides.

              Nearshore - In beach terminology, an indefinite zone extending
              seaward from the shoreline well beyond the breaker zone.

              Nourishment - Process of replenishing a beach either naturally by
              longshore transport, or artificially by delivery of materials
              dredged or excavated elsewhere.

              offshore - (1) (Noun) In beach terminology, comparatively flat zone
              of variable width extending from the breaker zone to the seaward
              edge of the Continental Shelf.     (2) (Adjective) Direction seaward
              from the shore.

              OvertopRinq -  Passing of water over a structure from wave runup or
              surge actlon.

              Peat - Residual product produced by partial decomposition of or-
              ganic matter in marshes and bogs.

              Peat Pot (vegetation) - Pot formed from compressed peat and filled
              @i_i@ther with soil or peat moss in which a plant or plants, grown
              from seed, are transplanted without being removed from the pot.

              Perched Beach - Beach or fillet of sand retained above the other-
              wise normal profile level by a submerged dike or sill.

              Perigean Tides   Increased tidal ranges that occur each month when
              the moon is closest to the earth (perigee).

              Permeable - Having openings large enough to permit free passage of
              appreciable quantities of sand or water.

                                              165

              Pile - Long, heavy section of timber, concrete or metal driven or
              Te-tted into the earth or seabed as support or protection.

              Pile, Sheet - Pile with a generally slender, flat cross section
              driven into the ground or seabed and meshed or interlocked with
              like members to form a diaphragm, wall, or bulkhead.

              Piping - Fluidizing of backfill or an embankment to the extent that
              large quantities of material are pumped by wave action through
              holes under or through a bulkhead or revetment.

              Plasticity - As applied mainly to clay, the relative ease with
              which the material yields or deforms under pressure.

              Plug - core containing both plants and underlying soil, usually cut
              with a cylindrical coring device and transplanted to a hole cut by
              the same device.

              Polyvinyl Chloride (PVC) - Plastic material (usually black) that
              forms a resilient coating suitable for protecting metal from corro-
              sion.

              Profile, Beach - Intersection of the ground surface with a vertical
              plane that may extend from the top of the dune line to the seaward
              limit of sand movement.

              PVC - (see POLYVINYL CHLORIDE).
                           I
              Ravelling - Progressive deterioration of a revetment under wave
              iiE`tion.

              Refraction (of water waves) - (1) Process by which direction of a
              wave moving in shallow water at an angle to the contours is
              changed. Part of the wave advancing in shallower water moves more
              slowly than the part still advancing in deeper water, causing the
              wave crest to bend toward alinement with the underwater contours.
              (2) Bending of wave crests by currents.

              Revetment - Facing of stone, concrete, etc., to protect a scarp
              embankment, or shore structure against erosion by waves or cur-
              rents.

              Rhizome - Underground stem or root stock. New shoots are usually
              produced from the tip of the rhizome.

              Riprap - Layer, facing, or protective mound of stones randomly
              placed to prevent erosion, scour, or sloughing of a structure or
              embankment; also, the stone so used.

              Rubble - (1) Loose, angular, waterworn stones along a beach.     (2)
              Rough, irregular fragments of broken rock or concrete.

                                             166

              Runup - The rush of water up a structure or beach on breaking of a
              wave.   Amount of runup is the vertical height above stillwater
              level that the rush of water reaches.

              Sand - Generally, coarse-grained soils having particle diameters
              between 0.18 and approximately 0.003 inches.         Sands are inter-
              mediate between SILT AND GRAVELS.

              Sandbag - Cloth bag f illed with sand or grout and used as a module
              in a shore protection device.

              Sand Fillet- Accretion trapped by a groin or other protrusion in
              the lit     1 zone.

              Scour - Removal of underwater material by waves or currents, espe-
              a=ally at the base or toe of a shore structure.

              Screw Anchor - Type of metal anchor screwed into the bottom for
              holding power.

              Seawall - Structure separating land and water areas primarily to
              prevent erosion and other damage by wave action.        See also BULK-
              HEAD.

              Semidiurnal Tide - Tide with two high and two low waters in a tidal
              day, each high and each low approximately equal in stage.

              Setup, Wind - Vertical rise in the stillwater level on a body of
              water caused by piling up of water on the shore due to wind action.
              Synonymous with wind tide and STORM SURGE. STORM SURGE usually
              pertains to the ocean and large bodies of water. Wind setup usu-
              ally pertains to reservoirs and smaller bodies of water.

              Shallow Water - Commonly, water of such a depth that surface waves
              are noticeab y affected by bottom topography.       It is customary to
              consider water of depths less than one-twentieth the surf ace wave-
              length as shallow water.

              Sheet Pile - see PILE, SHEET.

              Shoal - (noun) Rise of the sea bottom from an accumulation of sand
              or other sediments.      (verb) - (1) to become shallow gradually.
              (2) To cause to become shallow. (3) to proceed from a greater to a
              lesser U-epth of water.

              Shoot - Collective term applied to the STEM and leaves or any
              growing branch or twig.

              Shore - Narrow strip of land in immediate contact with the sea,
              including the zone between high and low water lines. A shore of
              unconsolidated material is usually called a beach.

                                               167

               Shoreline - Intersection of a specified plane of water with the
               shore or beach (e.g., the high water shoreline would be the inter-
               section of the plane of mean high water with the shore or beach).
               The line delineating the shoreline on National Ocean Survey nauti-
               cal charts and surveys approximates the mean high water line.

               Sill - Low offshore barrier structure whose crest is usually sub-
               merged, designed to retain sand on its landward side.

               Silt - Generally refers to fine-grained soils having particle
                r__
               Uiameters between 0.003 and 0.00015 inches.        Imtermediate between
               CLAY and SAND.

               Slope - Degree of inclination to the horizontal. Usually expressed
               as a ratio, such as 1:25 or 1 on 25, indicating 1 unit vertical
               rise in 25 units of horizontal distance; or in degrees from hori-
               zontal.

               Sloughing - Process where a weakened mass of soil fails and moves
               downslope.

               Sprig - Single plant with its relatively bare roots, as pulled
               apart from a clump and used for transplanting.

               Spring Tides - Increased tidal ranges that occur semimonthly when
               the moon is new or full and the pull of the sun and moon are nearly
               in phase. The spring range is larger than the mean range for semi-
               diurnal or mixed tides.

               Stem - Main axis of a plant, leaf-bearing and flower-bearing, as
               air-s-tinguished from the root-bearing axis.

               Stillwater Level - Elevation that the surface of the water would
               assume if all wave action were absent.

               Storm Surqe - Rise above normal water level on the open coast due
               Eo -action of wind on the water surface. Storm surge resulting from
               a hurricane also includes the rise in level due to atmospheric-
               pressure reduction as well as that due to wind stress. See SETUP,
               WIND.

               Suspended Load - Material moving in suspension in a turbulent
               field.

               Swell - Wind-generated waves travelling out of their generating
               area.   Swell characteristically exhibits a more regular and longer
               period and has flatter crests than waves within their fetch.

               Tidal Period - Interval between two consecutive like phases of the
               tide.
               Tidal IRanqe - Difference in height between consecutive high and low
               (or higher high and lower low) waters. The mean range is the dif-

                                                 168

              ference in height between mean high water and mean low water. The
              diurnal range is the difference in height between mean higher high
              water and mean lower low water.    For diurnal tides, the mean and
              diurnal range are identical.   For semidiurnal and mixed tides, the
              spring range is the difference in height between the high and low
              waters during the time of spring tides.

              Tide - Periodic rising and falling of water resulting from gravi-
              Ta-T-lonal attraction of the moon, sun and other astronomical bodies
              acting upon the rotating earth.    Although the accompanying hori-
              zontal movement of the water resulting from the same cause is also
              sometimes called tide, it is preferable to designate the latter as
              tidal current, reserving the name TIDE for vertical movement.

              Tide, Ebb - See EBB TIDE.

              Tide Station - Place at which tide observations are being taken. A
              primary tide station is a location where continuous observations
              are taken over a number of years to obtain basic tidal data for the
              locality. A secondary tide station is operated over a short period
              of time to obE-ain data for a specific purpose.

              Tiller - A plant shoot which springs from the root or bottom of the
              original plant stalk.

              Topography - Configuration of a surface, including relief, position
              of streams, roads, buildings, etc.

              Transplant - SHOOT or CULM removed from one location and replanted
              in another.

              Trough of Wave - Lowest part of a waveform between successive
              crests. Also, that part of a wave below stillwater level.

              Tropical Tides - Tides that occur  .semimonthly when the declination
              of the moon is maximized.   During these times, the diurnal range
              tends to be greatest.

              Updrift - Direction opposite the predominant movement of littoral
              materials in longshore transport.

              Wake (boat) - Waves generated by the motion of a vessel through
              water.

              Wale - Horizontal beam on a bulkhead used to transfer horizontal
              loads against the structure laterally along it and hold it in a
              straight alinement.

              Waterline - Juncture of land and sea. This line migrates, changing
              with the tide or other fluctuation in water level. Where waves are
              present on the beach, this line is also known as the limit of
              backrush. (Approximately, the intersection of land with the still-
              water level.)

                                             169

              Wave - Ridge, deformation, or undulation of the surface of a
              liquid.

              Wave Climate - Normal seasonal wave regimen along a shoreline.

              Wave Crest - Highest part of a wave or that part above the still-
              water level.

              Wave Diffraction - See DIFFRACTION.

              Wave Direction - Direction from which a wave approaches.

              Wave Height    Vertical distance between a crest and the preceding
              trough.

              Wavelength     Horizontal distance between similar points on two
              successive waves measured perpendicular to the crest.

              Wave Period - Time in which a wave crest traverses a distance equal
              to one wavelength. Time for two successive wave crests to pass a
              fixed point.

              Wave Refraction   See REFRACTION (of water waves).

              Wave Steepness   Ratio of wave height to wavelength.

              Wave Train   Series of waves from the same direction.

              Wave Trough   Lowest part of a wave form between successive crests.
              Also, that part of a wave below stillwater level.

              Weep Hole - Hole through a solid revetment, bulkhead, or seawall
              for relieving pore pressure.

              Wind Setu2 - See SETUP, WIND.

              Windward   Direction from which wind is blowing.

              Wind Waves - (1) Waves being formed and built up by wind.         (2)
              Loosely, any waves generated by wind.

                                             170

                                      LITERATURE CITED

             American Wood Preservers' Association, "Standard C18-77: Standard
             for Pressure Treated Material in Marine Construction", 1977.

             American Wood Preservers Institute, 11AWPI Technical Guidelines for
             Pressure  Treated Wood - S2 Bulkheads:    Design and Construction -
             Part 1", 1970.

             Bertram, G. E., "An Experimental Investigation of Protective
             Filters", Harvard University Publication 267, January 1940.

             Davis, A. P., Jr., "Evaluation of Tying Materials for Floating Tire
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             Island, April 1977.

             Giles, M. L. and Eckert, J. W., "Determination of Mooring Load and
             Transmitted Wave Height for a Floating Tire Breakwater", CETA 79-4,
             U. S. Army Corps of Engineers, Coastal Engineering Research Center,
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             Hall, J. V., Jr., and Jachowski, R. A., "Concrete Block Revetment
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             Harris, D. L., "Tides and Tidal Datums in the United States", SR 7,
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             Ft. Belvoir, Virginia, February 1981.

             Hobson, R. D., "Review of Design Elements for Beach Fill Evalua-
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             Lambe, T. and Whitman, R. W., Soil Mechanics, John Wiley and Sons,
             Inc., New York, 1969.

             Mather, B., "Factors Affecting the Durability of Concrete in
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             Neill, C. R., "Dynamic Ice Forces on Piers and Piles: An Assess-
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             Journal of Civil Engineering, Vol. 3, 1976, pp. 305-341.

             Seelig, W., "Estimation of Wave Transmission Coefficients for
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             Stoa, P. N., "Revised Wave Runup Curves for Smooth Slopes", CETA
             78-2, U. S. Army Corps of Engineers, Coastal Engineering Research
             Center, Ft. Belvoir, Virginia, July 1978.

                                            171

               Stoa, P. N., "Wave Runup on Rough Slopes", CETA 79-1, U. S. Army
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               Thom, H.C.S., "New Distributions of Extreme      Winds in the United
               States", Journal of the Structural Division,     ASCE, No. ST7, July
               1968, pp. 1787-1801.

               U. S. Army Corps of Engineers, "Plastic Filter   Fabric", Civil Works
               Guide Specification CW 02215, Office, Chief of Engineers, Washing-
               ton, D. C., 1977a.

               U. S. Army Corps of Engineers, "Regulatory Program of the Corps of
               Engineers", Federal Register, Vol. 42, No. 138, Washington, D. C.,
               Tuesday, 19 July 1977b.

               U. S. Army Corps of Engineers, "Shore Protection Manual", Coastal
               Engineering Research Center, Ft. Belvoir, Virginia, 1977c.

               U. S. Army Corps of Engineers, "Geneva State Park, Ohio, Shore
               Erosion Control Demonstration Program, Preconstruction Report",
               Engineer District, Buffalo, February 1978a.

               U. S. Army Corps of Engineers, "Pickering Beach, Delaware: Precon-
               struction Report", Engineer District,     Philadelphia., April 1978b.

               U. S. Army Corps of Engineers, "Kitts    Hummock, Delaware: Precon-
               struction Report", Engineer District,     Philadelphia, April 1978c.

               U. S. Army Corps of Engineers, "Help     Yourself:   A Discussion of
               Erosion Problems on the Great Lakes      and Alternative Methods of
               Shore Protection", Engineer Division, North Central, September
               1978d.

               U. S. Army Corps of Engineers, "Bank    Erosion Control with Smooth
               Cordgrass and Saltmeadow Cordgrass on   the Atlantic Coast", TN-V-2,
               Coastal Engineering Research Center,    Ft. Belvoir, Virginia, March
               1980a.

               U. S. Army Corps of Engineers, "Engineering and Design: Ice Engi-
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               October 1980b.

               U. S. Army Corps of Engineers, "Monthly Bulletin of Lake Levels for
               the Great Lakes", Engineer District, Detroit, March 1981a.

               U. S. Army Corps of Engineers, "Method of Determining Adjusted
               Windspeed, U . for Wave Forecasting", CETN-I-5, Coastal Engineering
               Research Cen er, Ft. Belvoir, Virginia, March 1981b.

               U. S. Army Corps of Engineers, "Revised Method for Wave Forecasting
               in Shallow Water", CETN-1-6, Coastal Engineering Research Center,
               Ft. Belvoir, Virginia, March 1981c.

                                               172

            U.S. Army Corps of Engineers, "Low Cost Shore Protection: Final
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            U S. Navy, Naval Facilities Engineering Command, "Soil Mechanics,
            Foundations and Earth Structures", NAVFAC DM-7, Washington, D. C.,
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            United States Steel Corporation," Steel Sheet Piling Design Man-
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            Watson, L., Machemehl, J. and Barnes, B., "Deterioration of Asbes-
            tos Cement Sheet Material in the Marine Environment", Proceedings
            of the Coastal Structures 179 Conference, Vol. I., pp. 230-249,
            1979.

            Weggel, J. R., "Maximum Breaker Height", Journal of the Waterways,
            Harbors and Coastal Engineering Division, ASCE, Vol. 98, No. WW4,
            Paper 9384, 1972.

            Wiegel, R. L., "Waves, Tides, Currents, and. Beaches:   Glossary of
            Terms and List of Standard Symbols", Council on Wave Research, The
            Engineering Foundation, University of California, 1953.

            Winterkorn, H. F., and Fang, H. Y., Foundation Engineering Hand-
            book, Van Nostrand Reinhold Company, New York, 1975.

            Wortley, C. A., "Ice Engineering Guide for Design and Construction
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            sity of Wisconsin, Madison, Wisconsin, 1978.

                                            173

                                                           "AN

                                                 V;

             LE

                                            U-S Army Corps of Engineers
                                                        1981

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