Low cost shore protection a guide for engineers and contractors

[From the U.S. Government Printing Office, www.gpo.gov]

1/0
"w
Al
vv

@,; w =

4-:4 -@--

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

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

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

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

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

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

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

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.

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

-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

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.

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).

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

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.

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-

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.

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.

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

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.

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

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

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

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,

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

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.

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

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.

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-

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

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.

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.

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

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)]

+ 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

1980 1981 1982
MAY OCT NOV DEC MMAY JUN @ JUL AUG S OCT NOV ' JANTFEB W..JUN Ft.
I @--- ---.,-T - -.-, -,I --- - - -TE-C
F 67iiik-l -APRI"--'
N,,!, @FIII IIIAAI
.......... . .... . ......... ..... . .........
............ . .. . . .... . .......... .
..... ...... . . . . ............ . .......
..... ...... . ...........
...........
T97
wn 5
_1973 1,@73
......... .

. . ........ ....
... . . . ......
i 4973@1971 L03 1973
@ 4,- - - +4
. ... ......... ..
in

--- - -- . ....... 1977
.-7:.
-4
. . ............
a
.3;
.... ...... . . .....
.... . . . .. .........
-.1 . . ........... ....... . . .. . ..... ....... ...... . . . .... ....
12 1-42
....... ...
-4-
...... ............ . ... ... . .... ... .
..... . .. .........
+1 -4- +1
7=11, -4.1--,@-
.. . ......... ......... . .. ..........
.......... ... .... . . . .......
............ . .....
iRS 1934 . . ... ........
19 4 r9jw 19341
0 0
LO
-7-
3- 95
. . ....... . n -5 -.1 1.4
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
.. ....... .
. . . ........ . ......... . . .........
. . . . . ........... ... ..........
-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,�
........... ....... . .......... ...... . ..
..........
+ . .......... . ....
3 +3,
F77P . . ......... ...
..... ...........
E@
i 0 -. . . . ...........
...... ............ .. ............ ......... .
-7.
. ... . . .........
+2

. . ....... ........
..... ..... .. ............ . ...... ...
. . . . .............
.... ...........
_J I . ......... --- :777;
-4- t
+1
....... ... ........ ... -- . . . . . ....... ............
..... ........
. . ............ ....... . . ............
.. . . .........
CA'R -DATU 5-T 8 (1 ....... .... . . ...... -.... ....... . ..
0@
0@717
...... .......
.... ......
. ....... .. . ........
....... . ...... . ... ...........
-1 -1064 ID9, . . . . . .........
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

NOTE'
Values of storm setup are in feet.

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

(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

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

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

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

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,,

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)

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)

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,

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

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

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

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-

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

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.

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,

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)]

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.

F><1

EXISTING
RELINE BULKHEAD--,,,
Z

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

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

BREAKING
WAVES (Without Flonk Protection)

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

RETURN BULKHEAD RETURN
WALLS WALLS

BREAKING WAVES

(With Flonk Protection)

Figure 25 Flank Protection
RETURN
WAL LS

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).

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

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

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)]

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

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

V4FRT/CAL FACE
W L TH

SWI

SWL

Sw@L
1@
'o

Table 11 Wave Runup Heights

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

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.

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)

ANCHORED

CANFILEVER

Figure 28 Cantilever and Anchored Sheet Pile Bulkheads

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

@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@

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.

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.

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.

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.

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

--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

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.

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.

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

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

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.

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

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

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

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

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

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

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

AVI

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

COBBLETOP

FILTER FABRIC

JUMBO BLOCK GOBI (ERCO) BLOCK SHIPLAP BLOCKS

55/e
2.5'

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

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.

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.

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

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.

E,
4
"74 M'
A

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))

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.

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

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

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.

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.

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.

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

-, 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..

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.

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.

NCHOR
CHAIN

WAVE-MAZE +
DESIGN

BOLTS

Ff It

BAY

GOODYEAR
DESIGN

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

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.

1.20

1.00 100

0.80 64

M
z
M
0 0.60 36

@10
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

60
C

0040

[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

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

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).

4.2,

Figure 69 Surgebreaker Modules

106

iJ"
'@gzl

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

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.

IrA

_'T
AT
04

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.

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

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).

Figure 81 Timber Crib Groin

116

f fjAp
Nio

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)

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.

AV
;YI

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
pil 2
2
1A .3 4
4
F-j 10 ;2 5
2
lr-j .7: ..........
3 brd -@o@
S*
G
14 IL 4
8
6" 0
990
'7
i e
12"10 35
2 12
2
2 10 2

2 ... . ..........
4
33 9 Ms,kv
2
2 22 4 12
'c'
q"11.4 7i :17"."- SA4"4,,2 12 2

2
20.: IS..
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
7
-4-
2
17 16 3
7 S)*
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