ESTUARINE SHORELINE
DEVELOPMENT HANDBOOK
Environmental
Erosion Control and
Rehabilitation Guidelines
United States
Environmental Protection
Agency
EPA 0S-C8-0105
September 1992
Printed on Recycled Paper

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CPA p+fe^i/o i f
Final Report
ESTUARINE SHORELINE DEVELOPMENT HANDBOOK
Environmental Erosion Control and Rehabilitation Guidelines
Prepared by
U.S. Environmental Protection Agency
Region IV, Atlanta, Georgia
September 30,1992
LIBRARY
US EPA Region 4
Atlanta Federal Center
100 Alabama St., SW
Atlanta, GA 30303-3104

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For information contact:
Dean A. Ullock
U.S. EPA, Region IV
345 Courtland St., N.E.
Atlanta, GA 30365
(404) 347-1740
This document was prepared with assistance from:
Battelle Ocean Sciences
397 Washington Street
Duxbury, MA 02332
With a subcontract to:
Offshore & Coastal Technologies - East Coast
A Division of Shorelines, Incorporated
510 Spencer Road
Avondale, PA 19311
The primary researcher for Offshore & Coastal Technologies
Dr. Bill Grosskopf

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CONTENTS
1.0 INTRODUCTION		1
Purpose	 1
Importance of Estuaries to the Environment		1
Cumulative Effects of Shoreline Development		1
2.0 ENVIRONMENTAL EFFECTS OF ESTUARINE SHORELINE DEVELOPMENT		4
Filling of Habitat		4
Dredging		4
Circulation Modification 		4
Scour and Sedimentation 		5
Runoff		5
Shading of Vegetation		5
Human Use 	5
3.0 SHORELINE DEVELOPMENT DESIGN CONSIDERATIONS	6
Water Levels 	6
Wave Heights	6
Soils Conditions 	6
Shoreline Characteristics 	7
Sedimentation Control	8
Materials	8
Required Lifespan 	8
General Design Methodology 	9
4.0 SHORELINE DEVELOPMENT ALTERNATIVES		11
Shoreline Erosion Control 		11
Vegetation		11
Sills		12
Beach Fill 		14
Breakwaters 		17
Revetments		19
Groins 	21
Bulkheads 	23
Other Options	24
Water Access Construction	24
Launch Ramps 	24
Piers and Pilings	26
Boat Mooring Slips	27
Boat Houses	28
Shoreline Habitat Rehabilitation	28
Vegetation		29
Toe Stone and Sills	29
Artificial Reefs 		30
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Estuarine Shoreline Development Handbook
5.0 CONCLUSIONS	31
Environmental Impacts 		31
Combined Techniques	31
Professional Guidance	34
5.0 APPENDIX: ADDITIONAL INFORMATION 		37
TABLES
1	Planting Specifications for Erosion Control		12
2	Shoreline Development Impact Matrix		33
3	Shoreline Human Use Impact Matrix		34
4	Shoreline Erosion Control Applicability Matrix 		35
5	Shoreline Erosion Control Selection Matrix		37
FIGURES
1	Shoreline Development Before and After Vegetative Erosion Control	3
2	Evaluation of Tides, Surges and Wave Runup on a Beach	7
3	Filtering for Stone Structures 	9
4	Example of Flank Protection	 10
5	Schematic of Stone Sill with Marsh Creation	 14
6	Stabilized Shoreline Using Sill and Marsh Grass	 15
7	Cross-Section of Typical Beach Fill Project	 16
8	Schematic Plan View of Shoreline Response to Offshore Breakwater 	 18
9	Offshore Breakwater Project	 19
10	Typical Revetment Section	20
11	Functioning Revetment 	21
12	Rubble-Mounted Groin 	22
13	Typical Cross-Section for Bulkhead	 24
14	Example of Well-Designed Project	25
15	Indented Boatslip	27
16	Boat House Section 	29
17	Constructed Boat House 	 30
18	Construction Activities Along a Shoreline	 32
19	Plan View of a Simple Shore Erosion Control Project 	 36
IV

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Estuarine Shoreline Development Handbook
1.0 INTRODUCTION
PURPOSE
The "Estuarine Shoreline Development Handbook"
provides guidance to individuals, developers, and regulatory
agencies who are involved with shoreline erosion control
measures, water access construction, and shoreline
rehabilitation in estuaries or similar semi-protected coastal
waters. It presents an overview of the environmental effects
of shoreline development on estuaries, shoreline
development design considerations, and a variety of shore-
line development alternatives. The various shoreline
development alternatives are then discussed in more detail,
outlining their effectiveness in various situations, their
environmental effects, and other considerations.
This handbook does not provide complete detailed
design or construction procedures for shoreline development
structures. Supplemental information can be found in the
sources listed in the appendix entitled "Additional
Information." Similarly, a complete discussion of
environmental considerations of estuarine development is
beyond the scope of this handbook, and additional sources
of information in this area are also included in the
appendix.
The handbook presents guidelines for coastal estuarine
construction which will minimize environmental effects to
the maximum extent practical. It should be recognized that
all coastal development will have impacts on the estuary.
Some areas may be so sensitive that no development should
be allowed. When coastal development or construction is
allowed, the best practices available should be followed to
minimize impacts. By following the guidelines outlined in
this handbook, shoreline erosion control measures and water
access construction can have minimal effects on estuarine
water quality.
IMPORTANCE OF ESTUARIES TO THE ENVIRONMENT
The importance of estuaries and coastal wetlands is
generally well recognized and publicized. Estuaries support
a large and valuable recreation industry, provide extensive
waterfowl and wildlife habitat, and play an essential role in
coastal fisheries. It has been estimated that 31 commercial
species of fish and shellfish, accounting for 88% of the total
fishery landings of the Southeastern United States, are
directly dependent on estuaries. In addition, many other
non-commercial species support recreational fishing which
provides pleasure for millions of people, as well as millions
of dollars to local economies.
Estuaries support some of the most biologically
productive ecological systems on earth. It has been esti-
mated that estuarine salt marshes produce up to 11,500
pounds of vegetation per acre per year. That is over twice
the average production per acre of wheat, corn, or rice
worldwide, and equals the most efficient of farms using
extensive fertilization, pesticides and herbicides. It is this
productivity that supports the vast fisheries, waterfowl, and
wildlife within the estuaries.
Estuaries are under increasing pressure as the population
in surrounding areas increase. The number of inhabitants
in coastal areas is increasing far faster than in other parts of
the nation. By the year 2000, it is estimated that 70 percent
of the nation's population will reside in coastal regions. As
this coastal migration occurs, so will the demands on the
limited resources of the estuaries.
CUMULATIVE EFFECTS OF SHORELINE DEVELOPMENT
The majority of estuarine shoreline development projects
proposed consist of minor construction: typically a few
hundred feet of shoreline might be involved, with only
minor filling or dredging to regrade the shoreline or
eliminate shoreline erosion. The effect of such a project
might be considered minor by the property owner or
developer who does not understand the level of scrutiny the
small project must undergo before a permit is issued.
However, the impact of shoreline development for a single
project must consider the cumulative effect of all such
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Estuarine Shoreline Development Handbook
development on the environment of the estuary. The
impact of a single project may indeed be minor: the impact
of hundreds of such projects in an estuary may have a
major effect on the ecology of the estuary.
As an example, the Sarasota Bay, Florida, National
Estuary Program has established that the bay's natural
habitats have been directly and adversely affected by
dredging, filling, and hardening of shorelines. Over the
past 40 years, development has reduced the amount of
native shoreline still in its natural state to only 22 %. Of the
developed shoreline, 45% is fronted with bulkheads, 10%
surrounded by riprap and 23% artificially filled. As the
cumulative result of numerous small shoreline development
projects, almost 80% of intertidal habitat has been lost in
Sarasota Bay. This has resulted in drastic reductions in
fishery productivity. Considerable effort is now taking
place to enhance the shoreline habitat through the use of
artificial structures and by returning the shoreline to a more
natural state.
The sequence of effects between disturbance to the
shoreline and impact to the estuarine environment is often
subtle and complex. The impact of many separate
disturbances may be minimal, while a single disturbance
may cause a profusion of effects. The purpose of this
handbook is to provide guidance for minimizing the impacts
of individual shoreline development projects, which will
help to minimize the cumulative effects on the estuarine
environment. An example of shoreline development project
that has been performed with consideration for environ-
mental impacts is shown in Figure 1.
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Estuarine Shoreline Development Handbook
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Estuarine Shoreline Development Handbook
2.0 ENVIRONMENTAL EFFECTS OF ESTUARINE SHORELINE DEVELOPMENT
Shoreline development can affect the estuary in a variety
of ways: some direct, such as dredging or filling, others
indirect such as increasing the runoff from driveways and
lawns or increasing the human use of an area due to
improved access. Some of the major impacts of shoreline
development are discussed below.
FILLING OF HABITAT
Filling of estuarine habitat behind bulkheads directly
impacts the environment by eliminating estuarine acreage,
but perhaps more importantly by converting ecologically
important shoreline habitat supporting a wide diversity of
plant and animal life to relatively sterile deep water habitat
at the base of the bulkhead. Filling of the shoreline is
necessary to some extent for many of the shoreline erosion
control or shoreline access construction projects discussed
in this report. It is important to consider the habitat
resulting from the construction when evaluating the
preferred alternative. Vegetative erosion control measures
will often require filling to provide a suitable substrate for
the marsh plants, but the habitat created may be more
biologically important than the shoreline they replace.
Similarly, a riprap revetment will provide a much more
diverse habitat than a bulkhead it might replace.
DREDGING
Like filling, dredging directly impacts the environment
by physically removing bottom material and any organisms
living there. The effects of dredging may be much more
widespread than the immediate area of material removal,
however. Dredging can greatly increase suspended
sediment in the water, decreasing the light level reaching
plant life on the bottom of the estuary, and impacting fish
or shellfish. Dredging alters the nature of the bottom, often
replacing productive shallow shoreline with deeper, less
productive waters. Pockets of deeper water are often
created by dredging operations, which can become isolated
areas of water low in dissolved oxygen with soft,
unproductive bottoms.
Disposal of the dredged material can often be as
detrimental to the environment as dredging itself. At one
time it was common to dispose of dredge spoil by
discharging into nearby marshes. This destroyed valuable
marsh habitat, leaving unproductive spoil areas in its place.
Underwater dredge disposal can smother organisms on the
bottom, concentrate suspended sediments in the water
column, and replace valuable bottom habitat with less
productive soft sediment substrate.
CIRCULATION MODIFICATION
Often dredging, filling, or shoreline construction will
modify the existing circulation patterns in the nearshore
area, adversely affecting the estuarine environment. Any
alterations which change the nearshore topography from a
gradually sloping bottom to deep water with a steep bank
are likely to increase the current velocity of the nearshore
area, making the area less useful as a nursery habitat for a
variety of aquatic organisms. Removing vegetation or
creating deeper water will also expose nearshore organisms
to increased predation by removing protective cover or
allowing larger fish to enter the area.
Other types of circulation modification which can be
detrimental to the estuarine environment include changes
due to channel dredging, which can introduce colder more
saline water into an area, or which can allow freshwater to
drain rapidly into the estuary instead of slowly filtering
through marsh areas and shallow waters. Dead end
channels and canals will often develop water quality
problems due to lack of sufficient tidal circulation or
flushing.
It will often be less of a disruption to the environment to
build a pier out to deep water rather than dredge a channel
or berth into the shoreline. If a berth is dredged into the
shoreline it is preferable to keep it as shallow as possible
and to streamline the ends to increase the circulation within
the berth.
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Estuarine Shoreline Development Handbook
SCOUR AND SEDIMENTATION
Any modifications to the shoreline which increase
bottom scour either during normal or storm conditions, or
which increase sedimentation in productive bottom areas are
harmful to the estuarine environment and should be
avoided. Construction of vertical bulkhead walls seaward
of the high water line will often induce scour during
storms, leading to loss of material at the toe of the wall.
Besides promoting failure of the wall, this can increase the
suspended sediment load in the estuary, and remove
nearshore bottom habitat. A sloping revetment wall of
rough rubble is much less likely to cause scour under storm
wave conditions.
Sedimentation includes the deposition of silt or sand
around structures which interrupt the normal flow of
material along the shoreline or nearshore area. This can
include shoreline erosion control structures such as groins,
which are designed to entrap sand moving along the
shoreline, or shoreline access structures such as boat ramps,
which can cause sedimentation problems if improperly
placed or designed.
RUNOFF
Runoff of contaminated rainwater can affect the water
quality of the estuary. Contaminants include fertilizers
from yards or agriculture, sediment from construction or
farm fields, oil and grease from parking lots and roadways,
sewage treatment effluent from municipal plants or
individual septic tanks, and industrial waste.
Proper design of shoreline erosion control and access
structures can minimize runoff impacts by providing for
elimination or filtration of the runoff before it reaches the
estuary. Parking lot and roadway drainage can be routed
through grassed swales or into stormwater detention ponds.
A buffer of vegetation can be left between lawns and the
water edge. Construction areas must be contained with
proper silt fencing and other drainage controls. A shoreline
protection design which incorporates vegetation can provide
a very effective filter for contaminated runoff.
SHADING OF VEGETATION
Nearshore submerged vegetation requires adequate
sunlight to survive. Shoreline access structures such as
piers and boathouses can shade the bottom a significant
portion of the day even when they are pile supported,
reducing the productivity of the bottom vegetation. This
effect can be minimized by keeping the structure an
adequate distance from the bottom, keeping the structure as
narrow as possible, and leaving spaces between decking
boards.
Trees planted along the shoreline can adversely affect
marsh grass by shading them. Marsh grass typically
requires about four hours of direct sunlight per day to
thrive, and shading can weaken it to the point where it can
no longer provide erosion control for the shoreline.
Shoreline erosion control projects incorporating vegetation
require careful consideration of the placement of shade
trees.
HUMAN USE
Shoreline access structures can increase human use of a
shoreline, with the potential for greater litter and foot
traffic. Shoreline access planning should include controls
to safeguard vulnerable vegetated areas. Boat ramps, piers,
moorings and boathouses will increase the boat traffic in the
vicinity of the structures. Care should be taken in siting
such structures to avoid areas of submerged aquatic
vegetation, which can be easily damaged by boat propellers.
Boat wakes can also increase erosion on vulnerable banks,
destroying shoreline vegetation and increasing sediment loss
into the estuary.
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Estuarine Shoreline Development Handbook
3.0 SHORELINE DEVELOPMENT DESIGN CONSIDERATIONS
In designing a structure, numerous decisions on structure levels, wave heights, and environmental impacts. Other
location, height and shape must be made. The factors most considerations include toe protection, soil properties,
important to structure design include water filtering, and flank protection.
WATER LEVELS
The maximum water level during storm conditions
determines required elevations of structures to prevent
overtopping and structural damage. In tidal waters, the
water level is a combination of the tide and a storm surge.
Spring tide levels can be determined from tide tables.
Storm surge levels can be determined from local experience
or from the local Flood Insurance Rate Map (FIRM)
published by the Federal Emergency Management Agency
(FEMA). The FEMA information for a particular area can
be requested by mail from FEMA, Flood Map Distribution
Center, 6930 San Tomas Rd., Baltimore, MD, 21227.
Typical storm tides range from 4 to 7 feet in coastal waters.
In the Gulf coast in extreme hurricanes the storm tide can
reach up to 20 feet.
WAVE HEIGHTS
Wave heights are governed by wind speed, fetch
(straight line open water distance to which a site is
exposed), and water depth. Coastal engineering design
manuals such as the U.S. Army Corps of Engineers "Shore
Protection Manual" (1984) provide charts for determining
wave heights. Wave heights can also be limited by the
depth of water at the site. The maximum breaking wave
height is approximately equal to the depth of water. If the
bottom material in front of a structure is easily eroded, such
as sand or soft mud, the water depth at the toe of the
structure may increase over time. In this case either toe
scour protection should be provided, or allowance should be
made for increased water depth due to scour.
Wave runup is the vertical height above the Stillwater
elevation that the rush of water reaches on a structumines
or beach after the breaking of a wave. Wave runup deter-
mines the height to which a shoreline erosion control
structure should be constructed to avoid overtopping and
damage to the back of the structure. Runup will typically
range from a vertical height equal to the incident wave
height for a stone revetment to twice the incident wave
height for a vertical faced bulkhead.
It is often not cost effective to eliminate all overtopping
by building an extremely tall structure. In many cases it
would be more economical to allow some overtopping
during large storms. In this case, the structure design
should incorporate measures to minimize erosion behind the
structure due to wave overtopping. This can include a rock
apron or paving behind a bulkhead or revetment, or
erosion-resistant vegetation such as turf grass planted
behind the structure. The extreme elevation to which tides,
surges and wave runup will reach is depicted in Figure 2.
SOILS CONDITIONS
Soil properties are important for determining the long
term stability of coastal structures. Settlement, pile
embedment, toe stability, and scour are determined by the
surface soil properties. For small private projects, the
knowledge of local contractors is often the best source of
information on requirements for pile embedment,
settlement, and scour. For larger projects, a soils
exploration program will be justified. General suitability of
various general soil types for coastal structures is as
follows:
o Gravel: Difficult driving for wooden or other light-
weight sheet piling. Excellent for stone structures.
• Sand, Silty Sands: Good for sheet piling, but toe
protection will be required. Suitable for stone
structures, but stone structures will also generally
require toe protection. Commonly found along beaches
and rivers.
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Estuarine Shoreline Development Handbook
Figure 2. Elevation of Tides, Surges and Wave Runup on a Beach.
(Univ. Wisconsin Sea Grant, 1987)
• Fine Grained Soils: Good for piles if firm. If soft, long
embedment lengths may be required. Good for stone
structures if firm. Excessive settlement may occur if
soft.
• Organic Soils, Peats: Generally not acceptable unless
piles bear on an underlying stratum. May result in large
settlement of stone structures unless the layer is thin.
These soils usually occur in low lying areas such as
marshes.
SHORELINE CHARACTERISTICS
There are a wide variety of shoreline types. Each type
of shoreline calls for different shore erosion control
solutions.
Banks and bluffs are steep shoreforms consisting of soft
erodible material such as clay, sand, or gravel. Bluffs are
typically higher than banks, but no clear distinction is
generally made. Bank erosion is typically due to a
combination of seepage of groundwater within the bluff and
erosion by wave action at the base. The most appropriate
erosion protection may consist of a combination of a
drainage system or slope flattening, plus wave erosion
protection such as a revetment at the toe.
Wetlands are marshy areas that are saturated with water
for much of the time and support vegetation adapted to
saturated conditions. Previously often drained or filled to
create new upland areas, marshes are now protected by
federal and state regulations. Protection of marshes will
often consist of a non-structural solution incorporating the
planting of erosion resistant marsh grasses.
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Estuarine Shoreline Development Handbook
Beaches are the most common shoreform in the United
States. Beaches are typically very dynamic, with the
sediment moving onshore, offshore, and along shore in
response to wind and wave conditions. Interrupting the
movement of sediment along the shoreline by constructing
jetties or groins can cause detrimental impacts to beaches
adjacent to the construction.
SEDIMENTATION CONTROL
Care must be taken during construction to minimize
sediment runoff into the estuary. Measures which can
easily be incorporated into shoreline construction include
sedimentation fences surrounding excavation and material
storage areas. Some areas may have restrictions on
construction during certain seasons to protect habitat or
marine organisms during particularly vulnerable stages.
MATERIALS
Structures constructed along the shoreline of estuaries
are exposed to severe conditions, including emersion in
seawater, exposure to marine organisms, and public use.
Materials used in their construction must be durable to
obtain a reasonable useful life. Some of the most common
materials include the following:
Rock is the most frequently used material for shoreline
erosion control. Rock is generally durable and cost
effective, when supplies exist within a reasonable distance
from the project. Dense, sound rock will give the best long
term performance.
Wood is used in many shoreline access structures, as
well as bulkheads. Wood used in the marine environment
should be chemically treated to resist rot and boring
organisms. Creosote-treated timbers should generally be
avoided due to the potential impact on the environment.
Concrete can provide a very durable construction
material for shoreline access or erosion control. Because
concrete is not as dense as quarrystone it is not as stable in
waves. Concrete is available as pour-in-place, precast, and
concrete rubble, depending on the application. Additives,
such as air entrainment, can increase the durability of
concrete in seawater. Care should be taken when using
concrete rubble to ensure that the material is free of
contamination such as petroleum products.
Metal is used in a variety of shoreline structures,
including bulkheads and shoreline access structures. Steel
with various properties and coatings is available to help
withstand corrosion in seawater. Aluminum is available for
small bulkhead walls.
Elastomeric materials such as plastic and rubber are used
for floating docks, floating breakwaters, fishing reefs, and
light-weight bulkheads. Care must be taken to ensure the
plastic is properly formulated to withstand sunlight to
provide a reasonable length of service.
REQUIRED LIFESPAN
Return period refers to the frequency of storms of a
certain severity and is used as a design criterion. For
instance, a structure can be designed to survive a storm
which occurs on the average of once in 10 years, i.e. a
return period of 10 years, more cheaply than it can be
designed to withstand a storm which occurs on the average
of once in 25 years. However, the risk that the structure
will be damaged during its lifetime will be greater for the
10-year design than the 25- year design. It is recommended
that permanent residential protection structures be designed
for a minimum return period of 10 years, and preferably 25
years. Structures designed for 10-year return periods can
be expected to require regular significant maintenance costs.
Structures designed for 25-year return periods will require
less regular maintenance, but may occasionally be damaged
by large storms. Major projects should be designed for a
50- to 100-year return period.
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Estuarine Shoreline Development Handbook
GENERAL DESIGN METHODOLOGY
There are a number of general procedures recommended
for the planning and design stages of shoreline construction
projects. These procedures will vary somewhat depending
on the size, scope, and type of project, but they provide a
general guide for planning.
•	Obtain general water depths governing navigation in the
vicinity of the site from navigation charts. For erosion
control structures, obtain cross-sections of the bank to be
protected.
•	For offshore access structures, measure water depths
offshore beyond the expected limits of the structure.
•	Estimate design water levels (tide plus storm surge) and
potential wave heights to determine the design wave
height for the site.
•	For erosion control structures, estimate the wave runup
on the structure.
•	Obtain information on soils in the area of construction.
•	Check with local agencies and the U.S. Army Corps of
Engineers for environmental limitations on construction
and for information on the permitting process.
•	Lay out the structure using the cross-section survey.
•	Consider the long term stability of the bottom in front of
the structure, the shoreline adjacent to the structure, and
the land behind the structure. Consider toe protection,
flank protection (see Figure 3), and filter layer (see
Figure 4).
There are a variety of available publications regarding
shoreline erosion control which can provide additional detail
on design methods. Examples include "Low Cost Shore
Protection -A Guide For Engineers and Contractors" (U.S.
Army Corps of Engineers, 1981) and "Shore Protection
Manual" (U.S. Army Corps of Engineers, 1984). It is
recommended that shoreline erosion problems be addressed
with the assistance of a coastal engineer.
INITIAL
POSITION
ML W ^7
Soil ond water passes through
gaps between stones
Groundwater
flow
FINAL
POSITION
Erosion
MLW \7 I con,inues
mlw^7
GRADED
STONE
FIL TER
Water easily flows through
structure
MLW 7
SYNTHETIC
FIL TER
CLOTH
oil particles
connot penetrate
filter.
»»*»•
^-Wat
Synthetic filter cloth
er can poss throuah filter
cloth but soil porticles cannot
Figure 3. Filtering for Stone Structures
(U.S. Army Corps of Engineers, 1981).
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Estuarine Shoreline Development Handbook
&
^EXISTING
( SHORELINE
BULKHEAD-

'»»>«»»><>-...<»>...[. »»»«» »«m x»nj<» >'»>«»<»¦> m n IMI|. (	^
(Initial Construction)
-BREAKING
WAV ES
RETREATEDs
SHORELINE
)	BULKHEAD—\ (
J	\ V	*****
\\/////S/;s//SSSS/SS//SSSS/SS>/?/SSSS777?f

BREAKING
WAVES

(Without Flank Protection!
RETURN
WALLS
<^c/
BULKHEAD"
BREAKING WAVES
RETURN
WALLS
(With Flank Protection)
Figure 4. Example of Flank Protection
(U.S. Army Corps of Engineers, 1981).
10
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Estuarine Shoreline Development Handbook
4.0 SHORELINE DEVELOPMENT ALTERNATIVES
SHORELINE EROSION CONTROL
Vegetation
a.	Site Characteristics. Vegetation is most effective as
a shoreline erosion control measure in relatively protected
areas where wave heights are limited. For vegetation
without auxiliary structures, such as those discussed in the
next section, this generally means the maximum fetch
(straight line length of open water) should be less than
about one mile. The site should also be characterized by
gentle slopes so a sufficiently wide band of shoreline
between mean low water and highwater exists to support
enough vegetation to effectively buffer the shoreline.
Generally 15 to 20 feet of vegetation is required to provide
adequate protection. A moderate tidal range on the order
of several feet and gently sloping banks are more conducive
to vegetation erosion control than are minimal tides and
steep banks.
b.	Environmental Consequences. Vegetated shorelines
for erosion control are environmentally advantageous unless
a healthy established ecosystem must be destroyed to
establish the erosion control. Generally the sites considered
for vegetation erosion control consist of eroding soil banks
or marsh edges. In the latter case, the edge of the marsh
is protected by establishing a gentle slope protected by new
marsh vegetation in front, leaving the existing marsh
undisturbed. With guidance from a professional coastal
engineer, new marsh plantings can provide the same
benefits to the estuary as does a natural marsh, including
shelter, food and nutrients for a wide variety of organisms.
c.	Human Shoreline Use. Vegetated shoreline control
will generally limit the amount of use a protected shoreline
can receive. The marsh grasses generally used are
vulnerable to damage by regular foot traffic, and a well
established stand of marsh grass is difficult to walk through.
If access to the shoreline is desired in an area being
considered for vegetated erosion control, special provisions
should be made. This could include elevated wooden
walkways, pocket sand beaches protected by groins, or
gravel walkways.
d.	Design Considerations and Limitations. Design of
vegetation erosion control projects will include the
following steps:
•	Evaluate Site: The best indicator of a site suitable for
vegetation erosion control is the presence of marsh
vegetation within a short distance, or other erosion
control projects in the vicinity.
•	Determine Water Levels: The zone which should be
planted with a particular species can be determined by
observations of nearby natural marshes. The
appropriate elevations for various common species is
shown in Table 1.
•	Sediment Supply and Stability: A moderate amount of
sediment deposition on marsh grasses can have a
beneficial effect by stabilizing exposed grass roots and
filling eroded areas. Where there is excessive
deposition, grasses can become irreparably damaged
due to burial. A beach or fill which erodes rapidly
after the marsh grass has been planted will result in
plants washing out. Fills should be allowed to come
to equilibrium before planting.
Additional information on vegetated erosion control can
be obtained from "Planting Marsh Grasses for Erosion
Control," by the University of North Carolina Sea Grant
Program. Local County Extension or Sea Grant agents may
have information on particular areas. The application of
marsh grass for erosion control can be extended through the
use of small structures, as discussed in the next section.
e.	Cost. Vegetation will typically be the most economic
method of shoreline erosion control for those areas which
are suited to the method. Costs might typically include
marsh plants for a 20-foot wide planting area, grading the
bank, and filling the shoreline with sand to provide a
uniform mild slope. Costs currently range from $20 to $50
per foot of shoreline (1992 cost estimate). Information
about local suppliers of plants can be obtained from the
U.S. Army Corps of Engineers, state, county or local
11

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Estuarine Shoreline Development Handbook
Table 1. Planting Specifications for Erosion Control
(U.S. Army Corps of Engineers, 1981).
Type
Planting Time Plant Form
Spacing
Location
Smooth Cordgrass March-May
Saltmeadow
Cordgrass
Gulf Cordgrass
Salt Grass
Black
Needle Grass
Common Reed
Mangroves
March-May
March-May
Spring
Spring
Spring
Feb.-March
Sprigs
IS week seedlings
6-month seedlings
or plugs
Sprigs
15-week seedlings
Sprigs
15-week seedlings
6-month seedlings
Seedlings
Seedlings
Sprigs
Seedlings established
Plants
3' apart
1.5' apart
1.5' apart
3' apart
1.5'-3' apart
1.5' apart
1.5' apart
1.5'-3'
1.5% of Cordgrass
plantings
1.5'-3'
1.5' apart
6'-10' apart
MLW to MHW
MHW to high tide
MHW and above
MHW and above
Above MHW
Above MHW
MTL and above
government offices that issue permits for coastal shore
protection projects.
f.	Expected Lifetime. The lifetime of a vegetated
shoreline erosion project will depend greatly on the
suitability of the site, storm occurrences, and care and
maintenance. For a site with a limited fetch with a well
established marsh the main cause of failure of the vegetation
will be neglect. Debris allowed to accumulate on the marsh
will kill vegetation, and should be removed on a regular
basis. Trees should be properly located to prevent shading
of the marsh grass. The best treatment to ensure a long life
is regular fertilization with a slow-release fertilizer. This
will keep the marsh grass healthy and dense, providing the
best protection against erosion.
g.	Cumulative Effects. The cumulative effects of
appropriately vegetated shorelines in any estuary will be
positive. Planting marsh grasses for erosion control will
help reverse the long history of destruction of marshes in
estuaries in the United States.
h. Regional Considerations. Atlantic coast marshes will
typically consist of smooth cordgrass (Spartina alternaflora)
below mean high water (MHW) and saltmeadow cordgrass
(Spartina patens) above MHW to the estimated highest tide.
Other common species will include black needle rush
(Juncus roemerianus), common reed (Phragmites
communis), and mangroves. Gulf coast marshes will
include gulf cordgrass (Spartina spartinae) and saltgrass
(Distichlis spicata). Both of these later species are planted
above MHW. Other regional considerations involve tidal
ranges. As noted previously, areas with minor tidal
variations are less likely to have sufficient intertidal area to
provide sufficient width for vegetation to provide reliable
erosion control. The exception to this will be areas which
have extremely flat shoreline, or which can be filled or
graded to provide very flat shorelines. Refer to Table 1.
Sills
There are a large number of shorelines in estuaries
which could benefit from vegetated erosion control, but
which are exposed to waves that are too large for the
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Estuarine Shoreline Development Handbook
vegetation to become established and stable. One
alternative which is often practical and economical is to
extend the range of marsh plantings with a protective
structure known as a sill. The sill is similar to a
breakwater, except it is much smaller and is designed to
provide protection to the fill and marsh plantings behind it.
Typically such a structure will be constructed from stone,
be located between mean low water (MLW) and one foot
below MLW, and have a crest elevation approximately a
foot above mean high water (MHW). An example of a
stone sill schematic is shown in Figure 5 and a stabilized
shoreline using this technique is presented in Figure 6.
a.	Site Characteristics. Sites suitable for vegetated
shoreline erosion control in conjunction with a sill typically
have fetches of one to three miles, although such projects
have been successfully built in areas with fetches much
greater than this. Other site characteristics are similar to
vegetated shoreline erosion control sites.
b.	Environmental Consequences. The environmental
consequences of sills, when combined with marsh planting
for erosion control, are very positive. A relatively minor
amount of habitat is lost below the sill structure as
compared to other erosion control alternatives because the
structure is relatively small in size. The small stones from
which the sill is constructed will provide habitat to a range
of organisms. The marsh plantings will provide the
environmental benefits discussed for the vegetated shoreline
erosion control.
c.	Human Shoreline Use. The use of sills in combina-
tion with marsh plants for erosion control places the same
constraints on human use as does vegetated erosion control
alone. In general, regular or intensive foot traffic must be
prevented on the marsh plants. Alternative access should
be provided if shoreline use is desired.
d.	Materials. Sills are normally constructed of graded
quarrystone. The size of the stones and the size and cross-
section of the sill are determined based on wave conditions.
e.	Design Methodology and Limitations. The design
process will include the basic considerations discussed in
Section III and the procedures for vegetative erosion control
discussed in the preceding section (Section 4). Other
considerations include the following:
a The sill is generally designed for shallow water with
the stability of the armor governed by the wave height
with the water level at the crest of the structure. At
higher water levels the structure is submerged,
compensating for the greater wave heights possible
with the greater depths.
° The crest height is generally set so that the toe of the
fill on the back side of the sill is 1.0 to 2.0 feet lower
than the crest.
0 In some cases, breaks in the sill should be provided to
allow water into and out of the marsh behind the sill.
The area behind these breaks should be carefully
designed to avoid unacceptable erosion in these areas,
either with a stable sand beach or additional low stone
riprap.
In some cases, a sill-like structure can be useful in
stabilizing an eroding edge of an existing marsh. Typically
clumps of marsh vegetation will be eroded by wave action,
creating a scarp, or vertical face, at the new marsh edge
that drops a foot or more into the water. This scarp will
continue to march landward as the marsh edge is eroded by
wave action even though the marsh itself is stable in waves
passing over the top of the plants. In this case the edge can
be stabilized by a sill built as close to the scarp as possible.
The area between the marsh and -sill is filled with sand, and
marsh grass planted. With the edge stabilized, erosion
generally is stopped and the marsh is stable in all wave
conditions.
f.	Cost. Next to vegetation alone, sills combined with
vegetation are generally the least expensive shoreline
erosion control methods. Costs include the sills themselves,
plus the costs of grading, filling and marsh planting.
Currently, typical current costs range from $75 to $150 per
foot of shoreline, although costs could be greater for deeper
water and more fill (1992 cost estimates).
g.	Expected Lifespan. The same comments on expected
lifetime listed for vegetated erosion control also apply to the
marsh grass portion of the sill shore protection system. In
13

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Estuarine Shoreline Development Handbook
FILL AND MARSH GRASS
ARMOR STONE
MHW
CORE STONE
FILTER CLOTH
MIN. 3 STONES AT TOE OF SILL
EXISTING GROUND
Figure 5. Schematic of Stone Sill with Marsh Creation.
addition, the sill should be periodically inspected for
damage. The small size of the stones often makes it easy
for limited damage to be repaired by hand. Special
attention should be paid to the toe of the structure and the
ends of the structures to ensure that they are not being
undermined by erosion. If this is occurring additional
stones may be placed in the eroding areas. With proper
maintenance, a stone sill erosion control system should have
an indefinite life.
h.	Cumulative Effects. The cumulative effects of sills
in combination with vegetation for shoreline erosion control
should consist of the same positive benefits to an estuary as
vegetation alone, including additional marsh habitat,
elimination of erosion, and filtering of runoff.
i.	Regional Considerations. The regional considerations
discussed previously for vegetated erosion control also
apply to the planted portion of sill projects. In addition, the
availability of economical supplies of stone will affect the
designs in some regions. Other materials such as concrete
may be more economical in areas where rock supplies do
not exist.
Beach Fill
Beach fill consists of sand applied to an eroding beach
area, or to an area where a recreational beach is desired.
In an estuary, a beach fill will typically be combined with
some type of fill-retaining structure such as groins,
breakwaters, or sills. Figure 7 shows a typical cross-
section for a beach fill project.
a. Site Characteristics. A site suitable for a beach fill
will typically consist of an already existing sand beach
which has been eroding, no longer offering adequate
protection to the shoreline. In some cases the erosion of
the beach may be due to the interruption of the natural
movement of sand due to other shoreline erosion control
structures. Beach fills are often used to fill between groins,
and behind breakwaters and sills to restore the natural
shoreline protection a beach provides. In an estuary where
the natural shorelines are typically irregular, sand beaches
generally must be confined by some type of natural feature
such as rock outcroppings (headlands), or man made features
such as groins. Small sand beaches often exist at the base
of banks and bluffs, which provide a steady source of sand
as they erode back. If the source of sand is cut off by an
erosion protection structure such as a bulkhead or revetment
the beach may quickly disappear.
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Estuarine Shoreline Development Handbook
Figure 6. Stabilized Shoreline Using Sill and Marsh Grass.
b.	Environmental Consequences. If beach fills are used
to replenish already existing beaches which are eroding, the
environmental impact to the area will generally be minor.
If sand fill is placed over a marsh bottom or some other
type of productive bottom, important habitat may be lost.
Generally, beach fills should only be considered for areas
already consisting of sandy beach.
c.	Human Shoreline Use. Generally, sandy beaches are
the most heavily used shorelines for recreation. A beach
fill can restore or create a highly desirable recreational
area, increasing human traffic and impacts. If a beach with
public access is created, there should be careful
consideration of the possible increased traffic, parking,
litter, and human waste. Environmental impacts can be
minimized by proper drainage of parking areas, providing
refuse containers and rest rooms, and regular cleanup.
d.	Materials. Beach fills are constructed of medium- to
coarse-grained clean sand. The selection of sand type and
gradation is based upon the type of beach use, the wave and
tidal conditions, sand availability and cost and other factors.
e.	Design Considerations and Limitations. Design
techniques for beach fills are described in U.S. Army Corps
of Engineers "Shore Protection Manual" (1984). Some of
the items important to proper beach fill design include the
following:
(1)	The beach fill material should have characteristics
similar to the natural beach. The grain size and grain size
distribution should be similar to, or slightly coarser than the
existing material.
(2)	The beach fill should be placed on a flat slope
similar to the existing beach slope. Generally slopes should
15

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Estuarine Shoreline Development Handbook
-Kberm
DESIGN WATER
LEVEL
LOW WATER
INITIAL FILL PLACEMENT
'ERODED BOTTOM EQUALS
DEPOSITED VOLUME
FINAL SLOPE
DEPENDS ON COARSENESS
.OF THE SAND
DESIGN WATER
LEVEL
LOW WATER
//////?
//////
' '/////////>>>>>/;, 		
— 	-	
*(/<'>-> /,,, f f, f,,,
FILL RESPONSE TO STORM WAVES
Figure 7. Cross-Section of Typical Beach Fill Project.
be in the range of 1:10 to 1:15, with finer material placed
on flatter slopes.
(3) The material can be initially placed on steeper slopes
to make construction easier, with final adjustment to natural
slopes taking place by wave action. In this case sufficient
material must be provided to create the desired beach width
after final wave adjustment.
Limitations to beach fills include the following:
(1) Beach fills generally cannot provide complete
protection to banks or bluffs under very high storm waves
and water levels. Sand will generally move offshore under
major wave attack, and then move back onshore under
more typical summer wave conditions.
(2) A small local fill of beach sand will be rapidly lost
to adjacent shorelines if it is not confined in some manner.
Either the beach fill should consist of a long stretch of
beach, or the fill should be confined by natural barriers
such as stone outcroppings (headlands), or manmade
structures such as groins or breakwaters.
f. Cost. The cost of beach fill will depend greatly on
the availability of local suitable sand sources. The cost of
sand with good access to nearby sand pits will be moderate,
in the same range as a sill and vegetation shoreline erosion
project, typically from $15 to $25 per ton. In some cases
sand may be available at low cost from nearby dredging
projects. If dredged material is considered for a beach fill,
it must be demonstrated that the material is suitable for
beach fill, and does not contain unsuitably fine material
which will be washed away by normal wave action. The
cost of periodic replacement of beach fill in areas
16

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Estuarine Shoreline Development Handbook
undergoing steady erosion should be considered when
planning beach fills.
g.	Expected Lifetime. The life of a beach fill will vary
greatly depending on the design, protection provided by
natural or manmade features, and storm conditions. If a
beach fill is placed in an area which has been undergoing
natural erosion, it can be expected that the placed fill will
also be eroded at a similar rate. Sufficient sand should be
placed to provide at least several years protection at average
erosion rates. If the sand fill is confined, it may last many
years without requiring additional placement. Past
experience with sand loss is the best guide to future sand
loss.
h.	Cumulative Effects. The cumulative effects of beach
fills will generally be minor if they are placed only in areas
of existing eroding beaches. The creation of recreational
beaches should be limited to areas where the sand fill will
not smother existing vegetation or valuable bottom habitat.
Other cumulative effects associated with greater recreational
use of the shoreline can be minimized if attention is paid to
parking, litter, and other human use problems.
i.	Regional Considerations. The major regional
difference in the suitability of beach fills will be due to the
existence of natural sand beaches. In estuaries with limited
existing sand beaches, more care must be taken to ensure
that existing valuable bottom habitat is not lost due to filling
with sand.
Breakwaters
Breakwaters have been used with increasing frequency
in recent years for shoreline erosion control in estuaries.
They can often be used as an alternative to bulkheads or
revetments, lessening the environmental impact. This type
of structure is typically placed offshore with sections on the
order of 100 feet long alternating with gaps of similar
dimension. The breakwater segment length, distance
offshore, and gap width are the major design features.
Shoreline response to offshore breakwaters is shown in
Figures 8 and 9.
a.	Site Characteristics. Breakwaters are often used in
areas with limited sand beaches fronting banks or bluffs.
In these cases, either additional sand accumulates behind the
structures by natural accretion, or sand is placed as part of
the erosion control project. The combination of the
reduction in wave height by the breakwater and the
additional width and height of the beach provides the
shoreline protection. Breakwaters are also used to protect
the seaward edge of marshes from erosion by reducing
incident wave energy.
b.	Environmental Consequences. The impacts of
breakwater construction on the environment include the loss
of bottom habitat under the structure, construction-related
disturbances such as temporary increased levels of
suspended sediment, and alterations to the shoreline along
the area protected. In many cases the loss of bottom habitat
under the structure is compensated by the new habitat
created in the stone breakwater. The area behind the
breakwater will become more protected, perhaps leading to
the accumulation of sand or finer sediments. The protected
area will, in many cases, provide an enhanced environment
for submerged aquatic vegetation. Marsh grasses will also
often thrive along the protected shoreline if they are planted
in suitable substrate.
c.	Human Shoreline Use. Offshore breakwaters are
often a good choice when access and continued use of sand
beaches fronting banks and bluffs is desired. They do not
interfere with access, or cover or destroy the beach as
revetments or bulkheads may. The distance breakwaters
are constructed from shore will control the pattern of sand
deposition along the beach. Sediment will deposit in areas
that are sheltered from wave energy. If the structures are
placed very close to the shoreline sand may accrete and
may eventually form a sand feature that extends from the
shoreline to the structure, blocking the longshore movement
of sand. Depending upon the project location, this blockage
of longshore sand transport may not be desirable because
neighboring shorelines may erode due to the blockage of
normal sediment supplied from the breakwater-protected
area.
d.	Design Considerations and Limitations. Proper
positioning of offshore breakwaters to obtain the proper
relationship of length, gap width, and distance offshore is
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Estuarine Shoreline Development Handbook
ORIGINAL
SHORELINE
TOMBOLO-
POSSIBLE DOWNDRFT
EROSION
'>7.
SHORELINE RESULTING
•FROM NATURAL ACCRETION
OR ARTIFICIAL FILL

J?
\
x BREAKWATER
Figure 8. Schematic Plan View of Shoreline Response to Offshore Breakwater.
necessary for proper performance. Therefore it is
recommended that professional assistance be obtained for
design of this type of shore protection.
Breakwaters may not be as practical as revetments in
some situations where complete protection against erosion
is desired for high banks or bluffs. Typically the
accumulated sand behind breakwaters provides excellent
erosion protection to the top of the beach; but with extreme
high water levels and storm waves, erosion can take place
in the bank above the beach. Breakwaters may also be less
economical or not practical in coastal areas where the water
becomes deep within a short distance from the shoreline.
e.	Cost. Breakwaters can vary considerably in cost,
depending on water depths, tide range, and sources of good
armor stone. Costs typically will be greater than for sills
or vegetation and similar to revetments and bulkheads.
Typical current costs range from $250 to $500 per foot
(1992 cost estimate).
f.	Expected Lifespan. Breakwaters will have a long
lifespan if designed properly and maintained on a regular
basis. Causes of premature failure of breakwaters include
toe scour and foundation failures, stone deterioration due to
poor stone quality, and stone displacement due to
undersized stone or deficient construction.
g.	Cumulative Effects. Extensive use of offshore
breakwaters within an estuary will lead to changes to the
character of the shoreline and to the bottom in the protected
areas. None of these changes are obviously detrimental to
the environment since equally productive habitats might be
created. The most important aspect to consider is the
character of the bottom and shoreline under consideration.
Extremely productive or valuable habitat such as submerged
aquatic vegetation, shellfish beds, or marsh areas should not
be covered or altered by breakwater construction.
h.	Regional Considerations. Offshore breakwaters will
be most useful in regions with shallow nearshore waters and
banks with a good supply of sand. Breakwaters are less
useful in areas with deep water near the shoreline and high
bluffs with little sand. Breakwaters will be more expensive
in areas without a local supply of good armor stone.
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Estuarine Shoreline Development Handbook
Revetments
Revetments are erosion-control structures generally
constructed directly on an eroding bank or shoreline.
Revetments consist of a rough sloping armored face, toe
protection to prevent scour at the base of the protection,
and a splash apron to prevent erosion of material behind the
structure due to wave overtopping. A typical cross-section
of a revetment is shown in Figures 10 and 11.
a.	Site Characteristics. Revetments are generally
suitable for protecting low banks from erosion when a
recreational beach is not required. In some cases beaches
may form or remain between a revetment and the water but
the revetment structure will often cover narrow beaches,
and scour from increased wave reflection may reduce the
amount of sand deposited in front of the structure.
b.	Environmental Consequences. Construction of
revetments can cause alterations to the shoreline and loss of
valuable nearshore habitat. This is especially true when the
revetment extends below MLW. In this case the shoreline
can be changed from a gently sloping vegetated shoreline
with extensive shallows to a steep shoreline with limited
shallow water. In other cases where the revetment is built
on a steep eroding bank, little habitat will be lost, and a
source of suspended sediments will be removed. In
general, revetments should not be built where they cover or
displace vegetated shorelines or nearshore bottom.
Revetments can be built landward of MLW resulting in less
impact and displacement of valuable habitat. Care should
be taken in these cases that the material seaward of the toe
is stable, since the revetment can cause increased bottom
stresses by reflecting a portion of the storm wave energy
seaward. Lawns are often planted to the edge of the
revetment, increasing runoff of fertilizers and pesticides into
the estuary. A buffer strip or drainage away from the
shoreline should be incorporated into the revetment design
to minimize this effect.
c. Human Shoreline Use. A revetment can improve the
view and increase upland property by allowing the owner to
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Estuarine Shoreline Development Handbook
OVERTOPPING
APRON

GRADED STONE
FILTER
ARMOR LAYER
TOE
PROTECTION
.MHW
-MLW

Figure 10. Typical Revetment Section.
plant a lawn almost to the waters edge. However,
revetments often restrict access along the beach, especially
at higher water levels. In some cases the revetment causes
beaches to erode completely, preventing access along the
shoreline at all water levels.
d. Design Considerations and Limitations. There are a
number of good guides to the construction of revetments
available, as listed in the appendix "Additional
Information." Some of the main concerns with construction
of revetments include
(1)	Adequate toe protection should be provided to
prevent damage due to removal of material at the base of
the structure. This is especially important for revetments
built on sand.
(2)	A revetment should be tied to adjacent structures or
properly stabilized at each end of the structure to prevent
erosion on either side of the structure which could cause
failure.
(3) Revetments can rarely be economically built high
enough to eliminate all wave runup and overtopping. The
area behind the structure should be designed to resist
erosion due to the wave overtopping. This can be done
with rock aprons and turf grasses.
e.	Cost. Revetments generally cost approximately the
same as offshore breakwaters, $250 to $500 per foot of
shoreline, with costs varying widely depending on wave
conditions, type of shoreline, and location.
f.	Expected Lifetime. Maintenance and repair will be
required to keep the structure in good condition, but if the
structure is properly designed for the local wave conditions
and the rock is of good quality, a revetment should last for
an indefinite period. One limitation to the life of a of the
revetment is the long-term stability of the seafloor at the toe
structure. If the seafloor erodes away, the revetment will
eventually fail unless additional toe stone is placed.
g.	Cumulative Effects. A large number of revetments
in an area will lead to changes in the composition of the
shoreline, eliminating shoreline vegetation which provides
20

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Estuarine Shoreline Development Handbook
valuable filtering of runoff into an estuary. Revetments
should be used for steep banks only where other shoreline
erosion methods incorporating vegetation are not acceptable.
Revetments will also increase scour below MLW at the toe
of the structure during storm conditions, eliminating shallow
water habitat and increasing suspended sediment loads.
h. Regional Considerations. Revetments are most
applicable to those regions with extensive eroding steep
banks, as opposed to shallow, vegetated shorelines.
Revetments are most economical in areas with local stone
supplies, although there are a large number of designs
incorporating precast concrete units.
Groins
Groins are small structures built perpendicular to the
shoreline to prevent the longshore movement of sand due to
oblique wave attack. These structures are sometimes used
to build beaches by trapping sand which would otherwise be
carried along the shoreline, but this can cause erosion of
other areas whose sand supply has been interrupted. Groins
are better used in conjunction with sand fill, to confine the
artificially-placed fill and maintain a healthy beach.
Figure 12 depicts the use of groins along a shoreline.
a.	Site Characteristics. Groins are best used along
existing beaches where stabilization of the beach is desired.
Filling between the structures with sand to prevent erosion
downdrifit of the groins is nearly always recommended.
Groins will be most satisfactory on beaches which are
oriented within 45 degrees of normal to the incoming
waves. Areas with waves at larger angles would require
extremely closely placed groins to create stable shorelines.
b.	Environmental Consequences. The major impact of
groins will be the loss of bottom habitat under the groin
itself, and under the sand accumulated between the
structures. Since groins are generally built only on sandy
beaches, the environmental impacts will generally be minor.
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Estuarine Shoreline Development Handbook
c.	Human Shoreline Use. Groins can be used to
stabilize sandy beaches, which can result in increased
human use of the shoreline. They can interrupt traffic
along beaches if the structures are large.
d.	Design Considerations and Limitations. The major
design features of groins are their length, height, and
spacing. These factors determine how effective the
structures will be in limiting sand movement. Improperly
design can accelerate loss of sand; therefore professional
guidance or local experience should be used when designing
these structures.
Another limitation of groins is that they do not prevent
the movement of sand offshore during extreme wave
conditions. Therefore sand may be lost in major storms,
exposing the bank to erosion. In addition, care must be
taken to ensure that groins do not cause increased erosion
further down the shoreline due to the interruption of the
natural movement of beach sand. This can be prevented by
filling the area between the structures with sand after
construction, so the natural movement of sand continues
over the groins.
e.	Cost. The cost of groins will vary greatly depending
on the site and scale of the project. An area with small
waves might consist of 20-foot groins with a spacing of 40
feet at a cost similar to a sill and vegetation, $7S to $150
per foot of shoreline. A more exposed area would require
longer structures with greater spacing, costing as much as
$250 to $500 per foot of shoreline (1992 cost estimates).
f.	Expected Lifetime. Groins can last indefinitely if
well designed and maintained. Erosion at the toe of the
structure, erosion of the bank at the landward end of the
structure, and material degradation can all lead to premature
failure of groins. Erosion at the toe of a groin can be a
special problem since groins are often built on sand
beaches, which are more susceptible to erosion.
g.	Cumulative Effects. If groins are confined to already
existing sandy beaches, the cumulative effects within an
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Estuarine Shoreline Development Handbook
estuary are expected to be small. Some alteration to the
shoreline takes place, especially if scour around the seaward
ends of groins removes bottom habitat and increases
suspended sediments. Generally, however, the shoreline
will retain its original characteristics and shoreline habitats.
h. Regional Considerations. Groins are best suited to
regions with existing sandy beaches and moderate tide
ranges and are less suited to marsh shorelines. The
structures can be constructed of stone or many other
materials, making them more attractive for sites without a
local supply of stone. Wood, steel and concrete sheet piles
are all commonly used for groins, although vertical-faced
structures consisting of these materials will increase scour
at the toe of the structure as compared to that occurring at
the toe of a groin constructed of stone.
Bulkheads
Bulkheads are vertical walled structures which retain fill
and protect the shoreline from erosion. Bulkheads are often
favored by landowners because they can extend the useable
dry land up to the waters edge, and in some cases provide
boat mooring at the property's edge. As discussed in the
introduction, bulkheads are associated with some of the
worst impacts on estuaries. Figure 13 shows a typical
cross-section for a bulkhead.
a.	Site Characteristics. Bulkheads have been used on
almost every type of estuarine shoreline. They are most
commonly associated with low banks, with the top of the
bulkhead above a typical high water elevation, and the land
sloping down to the landward edge of the bulkhead.
Bulkheads are also used to protect the toe of high banks and
bluffs, and the edges of marshes.
b.	Environmental Consequences. The major environ-
mental harm to estuaries from shoreline development has
been due to bulkhead ing and filling of marshlands to create
land developments. This has removed extensive marsh
habitat and shallow water habitat, replacing it with
unproductive deep water at the toe of the bulkhead which is
subject to increased scour during wave conditions due to
reflections off the vertical face. Bulkheads are in general
the least environmentally acceptable shoreline erosion
control alternative because they provide no habitat or
protected areas for marine life. The undesirable
environmental effects of bulkheads can be minimized by
building the bulkhead landward of the MHW line, with a
fringe of vegetation or rubble in front.
c.	Human Shoreline Use. Bulkheads provide good
access to the water edge for the homeowner, but generally
restrict movement along the shoreline by creating deep
water along the bulkhead.
d.	Design Considerations and Limitations. One major
environmental and maintenance problem with bulkheads is
scour at the toe. It is generally recommended that riprap
stone be placed at the toe of bulkheads to limit scour. The
riprap also provides additional habitat for marine
organisms. Bulkheads also frequently lead to direct runoff
from lawns and driveways. Buffer strips of vegetation
seaward of the bulkhead can help filter this runoff, or the
runoff can be channeled into swales which lead to marsh
areas to filter the water.
e.	Cost. Bulkheads are typically relatively expensive,
depending on the size and complexity. Typical bulkheads
will cost approximately the same as breakwaters and groins,
with current costs ranging from $250 to $500 per foot of
shoreline (1992 cost estimate).
f.	Expected Lifespan. The life of a wooden bulkhead
typically ranges from 10 to 30 years. Concrete bulkheads
can be expected to have longer lives, while the lifespan of
steel or aluminum bulkheads will depend greatly on the
environment and protection applied to the metal.
g.	Cumulative Effects. As discussed previously, cumu-
lative effects of bulkhead construction in estuaries has led
to significant modification of certain shorelines, associated
with the loss of considerable fishery production. The
proper design of bulkheads, primarily locating them above
MHW with a beach, riprap or vegetation seaward of the
bulkhead will help minimize these effects; but bulkheads
will, in general, have the largest effect on the environment.
h.	Regional Considerations. Certain estuaries have had
such extensive development and bulkhead construction that
additional bulkheading should be avoided. Other areas with
23

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Estuarine Shoreline Development Handbook
only limited existing bulkheads might allow bulkheads under
certain conditions if they are properly designed, and are
built above MLW.
Other Options
Other options which are often used in conjunction with
one or more of the above erosion control techniques include
infiltration and drainage controls and slope flattening.
These actions stabilize bluffs against erosion due to flowing
water and may be required even when all erosion due to
waves at the base of the bluff is prevented by a revetment
or some other means. An example of a well-designed shore
protection system might incorporate drainage control, slope
flattening, vegetation, and shoreline protection. Such a
project is shown in Figure 14.
Other options which must always be considered when
evaluating a particular situation include the following:
No Action consists of allowing nature to take its natural
course, without attempts to slow erosion. This option will
often have the least objectionable environmental
consequences and will obviously have the least cost. It may
not be acceptable because of continuing losses of property.
Relocation consists of removing vulnerable structures
from behind an eroding shoreline, either to another site or
far enough from the shoreline to give an acceptable service
life before again being threatened by erosion. This option
will also generally have minimal environmental impacts on
the marine environment.
WATER ACCESS CONSTRUCTION
Launch Ramps
A launch ramp is a sloping hard-surfaced structure used
for launching boats from trailers, and also in some
instances, providing water access to amphibious aircraft.
Boat ramps are built as public facilities, where they can
incorporate many lanes as well as piers, and as private
facilities, where they will typically be much simpler.
A splosh apron may be added	Dimensions and details to be
next to coping channel to	determined by particulor site
Figure 13. Typical Cross-Section for Bulkhead.
24

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Estuarine Shoreline Development Handbook
, Adequate Setback of Structures
' to Avoid Overloading Bank
and Provide Safety Factor
in Case of Bank Collapse
Construct Drain and Grade Surface
to Control Surface
Water
Well-Rooted Vegetation to Reduce
Surface Erosion
Regrade to Stable Slope
Provide for Drainage of Water
from Overtopping Waves
Stable Armor Stone on Stable Slope
* with Spaces Filled
Not Shown: Structure Ends Tied into Adjacent
Bank to Minimize Damage from
Flanking Erosion
Figure 14. Example of Well-Designed Project
(Univ. Wisconsin Sea Grant, 1987).
a.	Site Characteristics. Ramps are generally constructed
in areas where there is fairly deep water close to shore, and
where there is some protection from waves. Boat ramps
should be located in areas where they will not interrupt the
longshore movement of sand, since this may lead to an
accumulation of sand on the updrift side and erosion on the
downdrift side. Ramps should not be built in marsh areas.
b.	Environmental Consequences. The greatest impacts
of launch ramps are generally due to the activities
associated with the structures, not the structures themselves.
This includes increased boat traffic, channel dredging,
parking facilities, and increased human usage. Boats cause
wakes which can increase shoreline erosion and can damage
shallow beds of submerged aquatic vegetation. Boating
activities and noise can also disturb wildlife and nesting
birds. Parking facilities can cause runoff of contaminated
rainwater if not properly designed, and trash and debris will
often accompany the increased human use.
c.	Human Shoreline Use. Boat ramps will provide
access to the shoreline and the water body. This can allow
increased enjoyment and appreciation of an estuary, but it
can also create additional noise and traffic.
d.	Design Considerations. The following recommen-
dations are for heavily used public launching facilities.
Private boat launching ramps will typically be less
elaborate.
(1) Public launching ramp lanes should be 15 feet wide
on ramps of two or more lanes. If the launching ramp
consists of a single lane it is recommended that the lane be
20 feet wide, and never less than 16 feet wide. One
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Estuarine Shoreline Development Handbook
launching lane will handle approximately SO launchings and
50 retrievals per day.
(2)	A vertical curve should be incorporated into the head
of the ramp to provide a smooth transition between the
launching ramp and the parking area. The curve keeps
trailer hitches from striking the launching ramp at a change
in grade, and enhances the driver's vision while backing.
A 15- to 20-foot radius vertical curve is recommended.
(3)	Concrete is most commonly used for the construction
of heavily used launching ramps. Concrete should have a
minimum of 3 inches of cover over rebar. Precast concrete
planks should be designed to bolt, cable, or key together
during installation to prevent movement. Cast-in-place
concrete ramps should be finished with V-grooves aligned
at 60 degrees to the longitudinal axis of the ramp. This
provides traction on slick marine growth and aids in
cleaning the ramp.
(4)	In areas subject to currents or waves, the ramps must
be protected by a 3- to 5-foot perimeter of riprap or other
means of scour protection.
(5)	Where possible, parking areas should be located
immediately adjacent to the launching ramp. Parking areas
should be built on upland grounds, not filled intertidal
areas. Stormwater runoff from launch approaches and
parking areas should be filtered through sand or vegetated
areas and should not be directed down the boat ramp.
(6)	Garbage receptacles for marine trash should be
provided as close to the launching ramp as practical.
(7)	Some organizations have instituted public awareness
campaigns at public boat ramps, informing the boating
public of environmental impacts of boating on submerged
aquatic vegetation, bank erosion, and litter, and
recommending practices to minimize boating impacts.
e. Cumulative Effects. The construction of ramps will
cover a limited intertidal area, creating a minimal impact
from construction alone. The major impacts will be due to
the increased human us6, boat traffic, and associated
effects.
f. Regional Considerations. Heavily developed areas
will see much more of an impact due to boat ramps than
lightly developed or isolated areas. Areas with shallow
water and submerged aquatic vegetation will be more
affected by boat damage.
Piers and Pilings
Piers are structures designed to provide access from the
shoreline to deep water. Piers can be supported on pilings
or can be floating and are used for a variety of functions in
estuaries, such as mooring boats, fishing, supporting aids to
navigation and signs, and supporting other structures such
as bridges.
a.	Site Characteristics. Piers are built on a wide variety
of sites and shoreline types. They are suitable for most
bottom conditions. The length of pier will be governed by
the distance from shore to deep water. Fixed piers are used
under a wide range of tidal conditions, but floating piers
offer more convenient access to boats in areas where tides
exceed several feet.
b.	Environmental Consequences. Piers and pilings
cover a relatively small area of the bottom and hence are
generally not as damaging to the environment as solid fill
structures. Construction and pile driving can cause
temporary suspended sediments. Extensive groups of
closely placed pilings can alter currents and sedimentation
patterns. Pilings should be kept as widely spaced as
possible to minimize this effect. The major impact of piers
is due to shading of the bottom, reducing the productivity
of submerged vegetation. Some regions require that piers
be elevated at least one foot above the bottom for each one
foot of deck width to minimize shading. A 1-inch spacing
between deck boards can also increase the available light
under the pier. Wood treated with creosote is discouraged
because of its possible impact on marine life. Access to
piers through marsh areas should be by elevated walkway
to minimize damage to the plant life due to traffic.
Floating piers can cause a greater impact on sediment
transport and deposition, and should be avoided in areas of
large transport. Floating piers will also cause a greater
shading in shallow water since they are closer to the
26

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Estuarine Shoreline Development Handbook
ESTUARY
EBB
<	
Figure IS. Indented Boatslip.
bottom. Often fixed piers can be used at the shoreline to
minimize these problems, with floating piers used at the
seaward end in deeper water.
c.	Human Shoreline Use. Piers can attract the same
increased human use as boat ramps. This should be
considered when planning construction of a pier. Impacts
include parking problems and contaminated runoff from
parking lots, litter, increased boat traffic, and increased foot
traffic. Public piers should be handicapped accessible.
d.	Design Considerations. Piers and piling design
should be based on local conditions, including water depth,
the wave and tide environment, and geotechnical conditions.
Local knowledge will often be the best guide for small
private facilities. Larger facilities will require the services
of an engineer who will conduct proper geotechnical
investigations as part of the design process to determine pile
sizes and embedment depths.
Piers should not obstruct boat traffic or create hazards to
navigation. Piers, including the width of the boat moored
at the end, should not extend more than 1/4 of the way
across the water body.
All piers should have safety rails which meet the
applicable local construction codes.
e.	Expected Lifespan. Pilings of wood, concrete or
steel generally will have a lifespan of 30 years if properly
treated and maintained. Certain conditions, such as high
salinity and high temperatures, can shorten the lives of
pilings. Marine boring organisms can quickly destroy wood
which is not properly treated.
f.	Cumulative Effects. Cumulative effects of piers and
pilings will be caused by increased human use
accompanying their construction and in areas of dense
construction due to shading of the bottom. These effects
can be minimized by keeping piers as narrow as possible
and by joint use of a single pier instead of a number of
individual piers.
Boat Mooring Slips
Many property owners choose to moor their boats by
creating a boat slip from the upland portions of their
property in regions where this is permitted. In the past,
boat slips were dredged deep into the upland property
creating a square or rectangular boat slip with upland on
three sides. This type boat slip exhibits poor water quality
conditions because of the lack of flushing. This type of
boat slip is no longer permitted in many coastal areas. A
new type of boat slip (shown in Figure 15) is now being
constructed along the coast, with the slip parallel to the
shoreline and sides angled to allow better water flow.
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Estuarine Shoreline Development Handbook
"""fVlhiHWWH'
Other areas do not allow any dredging of uplands to create
boat slips. In these areas, boats are moored on piers
constructed to deep water.
a.	Site Characteristics. Boat slips are dredged into
banks which front deep water, so that access channel
dredging is minimal. No dredging through marsh areas is
allowable.
b.	Environmental Consequences. The impact of the
boat mooring slips includes suspended sediments and
destroyed nearshore and intertidal habitats during
construction. If the boat mooring is not properly designed
so that water circulation takes place, the water quality will
be degraded within the slip. The sides of the boat slip must
be properly stabilized with vegetation or riprap to prevent
continuing erosion and suspended sediment loads.
c.	Human Shoreline Use. The dredged mooring slip
allows individual property owners to moor their boats on
their property, increasing the convenience and enjoyment of
owning the boat.
d.	Cumulative Effects. A large number of dredged boat
slips will alter a portion of the shoreline from the natural
nearshore and intertidal habitat to a deeper dredged bottom
and steeper bank. The practice may also encourage
increased boating in nearshore shallow water, as opposed to
the deeper water near commercial marinas, piers, or public
boat ramps.
e.	Regional Considerations. The regulations governing
dredged boat slips varies from state to state. Not all states
allow individuals to dredge boat slips into upland areas.
Boat Houses
Often there is a need to protect moored boats from the
weather. In these cases boat houses are constructed over
the mooring area. In addition to a weatherproof roof, many
Boats are hoisted out of the water for additional protection.
A typical boat house is shown in Figures 16 and 17.
a.	Site Characteristics. Boat houses are built in the
same general type of sites and have many of the same
impacts as piers. Sites generally consist of those with
navigable depths of water near shore.
b.	Environmental Considerations. Environmental
effects are also generally the same as piers. Shading of
vegetation is of greater concern because of the larger area
of the roof. This can be minimized by leaving the sides of
the structure open and keeping walkways narrow to allow
as much light as possible on the bottom. Keeping the boat
out of the water when not in use will help eliminate some
of the impacts of boats on the environment, such as the
degradation of toxic bottom coatings and leaking of
petroleum products.
c.	Human Shoreline Use. Boat houses are for the
convenience of the boat owners. They should not be
allowed to become obtrusive or block access along public
shorelines. Boat houses can be kept less obtrusive by
keeping the sides open and by keeping them as close to the
shoreline as possible.
d.	Cumulative Effects. The environmental effects of
boat houses and the techniques for minimizing those effects
are similar to those of piers as described in Section 4.
SHORELINE HABITAT REHABILITATION
Loss of nearshore habitat has been associated with the
loss of fishery productivity of estuaries. This has primarily
been due to the construction of bulkheads and fill in marsh
areas. Some organizations are attempting to reverse this
situation by improving nearshore habitat along bulkheads
and revetments. The use of artificial reefs as fishery habitat
has become popular in some areas of the Southeast. Until
recently, this habitat creation has been restricted to deep
water and the enhancement of adult fish populations.
Shoreline habitat rehabilitation aims to create nursery
habitat for young fish. There are a number of methods
available to "soften" developed shorelines and return them
to a more natural state. Some of the most promising are
discussed below. For the most part, they are similar to
recommended minimal impact shoreline erosion protection
methods, with similar impacts and benefits.
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Estuarine Shoreline Development Handbook
ROOF
PILE v

1
e
X
i
&
y OPEN SDES
	MHW
~ "	 MLW
BOTTOM
/
/

/
/
/
Figure 16. Boat House Section.
Vegetation
a.	Site Characteristics. Vegetation will enhance the
nearshore habitat in any areas where it can survive. The
requirements for the survival of vegetation in the intertidal
zone were discussed in Section 4. Many sites with
bulkheads or revetments with toes above MLW will be
suitable for the establishment of vegetation, either with or
without the removal of the structure. Other areas can be
made suitable with stone sills and fill.
b.	Environmental Consequences. The re-establishment
of nearshore vegetation provides a protected area of shallow
water with cover from both aquatic and bird predators. The
vegetation also provides a food source for a wide variety of
aquatic life, which in turn provides a food source for fish.
As discussed previously, vegetation can also filter runoff
into an estuary, improving overall water quality.
c.	Design, Cost, and Lifespan will be the same as
described for a vegetated shoreline erosion control project
in Section 4.
Toe Stone and Sills
a.	Site Characteristics. Many sites which will not be
suitable for vegetation because of depth or wave action can
be improved by the application of stone along the toe of
vertical structures. Any bulkhead that is an adequate
distance from a navigable waterway is a candidate for toe
stone. Other areas could be improved by a sill built
seaward of a bulkhead or revetment, with fill supporting
vegetation planted behind the sill. Although deep water
seaward of a bulkhead will make the cost of this alternative
greater, there is no limit on water depth with this
alternative.
b.	Environmental Consequences. The application of
stone riprap at the toe of a bulkhead replaces a deep water
habitat subject to scour during storm events with a shallow,
stable nearshore environment. The voids and surfaces of a
stone surface provide habitat to a wide variety of marine
life and improve the habitat for juvenile fish.
c.	Design, Cost, and Lifespan considerations for sills
and toe stone are the same as those described in Section 4.
Toe stone will also improve the performance of a bulkhead
by preventing toe erosion and reducing runup and over-
topping during storms.
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Estuarine Shoreline Development Handbook
Artificial Reefs
a.	Site Characteristics. In many developed estuaries,
the bulkheaded canals formed by dredging and filling of
marshland are the least productive areas. The canals are
too deep to provide shallow habitat and too narrow for
extensive toe stone or other "natural" habitat enhancement
alternatives. Artificial reefs are structures designed
specifically for placement at the toe of bulkheads to attract
and support juvenile fish species.
b.	Environmental Consequences. The structures have
been designed to be lightweight and easily placed and will
attract a variety of marine life and provide shelter for young
fish. These structures are largely untested, although there
is currently one project as part of the Sarasota Bay National
Estuary Program evaluating a variety of designs for
effectiveness, lifespan, and stability.
c. Design Considerations. Regulatory agencies are
currently reluctant to allow large scale private placement of
materials in shallow water for habitat enhancement due to
concerns about navigation, shifting or drifting of unstable
structures, leaching of pollutants from unsuitable materials,
and esthetics. Permits are required for such work, just as
they are required for all other types of fills in estuaries.
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Estuarine Shoreline Development Handbook
5.0 CONCLUSIONS
ENVIRONMENTAL IMPACTS
Construction along the shoreline of estuaries for erosion
control or shoreline access will have a variety of impacts on
the environment, often causing a loss of habitat and reduced
productivity of marine life. The cumulative effect of a
large number of small individual projects can have a major
impact on the estuary as a whole. This cumulative
development has drastically reduced the water quality in
some of the more heavily developed estuaries in the
southeast United States in the last 40 years. Many other
estuaries are currently undergoing rapid development, with
the potential for loss of recreational and commercial
fisheries, loss of habitat for wildlife and waterfowl,
degradation of water quality, and spoiling the beauty of the
shoreline. A photograph of a shore protection project that
is under construction is presented in Figure 18.
These effects can be minimized by proper planning and
construction of shoreline structures. In many cases the
shoreline environment can be improved by incorporating the
best practices of shoreline erosion control. Each local
shoreline development project has the potential to either
improve conditions or degrade the environment further.
Table 2 is a Shoreline Development Impact Matrix which
provides information on the relative impact on the estuarine
environment of various types of shoreline development.
This matrix can be used to help choose the shoreline
development with the least impact to the environment. This
figure presents the negative and positive impacts of each of
the shoreline erosion control and shoreline access options
discussed in Section 3. Each option is evaluated in terms
of habitat loss (either dredging or filling), effects on
nearshore circulation, causing or improving scour of the
bottom or sedimentation along the shoreline, runoff from
upland areas, shading of vegetation, and the visual impact
of the shoreline when viewed from the water. The
evaluation is somewhat subjective and will vary greatly
from project to project, but the matrix provides a general
guide to shoreline development impacts on the environment.
There are a number of other elements in choosing an
optimal shoreline development structure, or evaluating a
development's total impact. Another important
consideration is summarized in Table 3, the Shoreline
Human Use Impact Matrix. Human use impacts are related
to how a development affects the recreational use of the
shoreline and how the human use impacts the environment.
The human use impact of each of the shoreline development
options is summarized in terms of boating, swimming,
fishing, walking along the shoreline, viewing the shoreline.
Impacts can vary greatly depending on the intensity of the
human use. For instance, a single homeowner may have
minimal impact walking along and fishing from a vegetated
shoreline; but if the same shoreline is accessible to the
public, vegetation may soon be destroyed.
The third element affecting the choice of shoreline
erosion control is the type of shoreline. Shorelines can
consist of a variety of different types, including marshes,
beaches, banks and bluffs. Some erosion control methods
will be more applicable to certain shoreline types than
others. Table 4 summarizes the suitability of the shoreline
erosion control methods to the various shoreline types.
Other factors which enter into the selection of a suitable
erosion control method for a particular situation include the
length of open water to which a site is exposed (fetch
length), which affects wave conditions, the range of water
levels at the site under normal and storm conditions, the
angle at which the waves strike the shoreline under storm
conditions, and the cost of the options. These factors are
summarized in Table 5, the Shoreline Erosion Control
Selection Matrix.
COMBINED TECHNIQUES
Examination of the shoreline erosion control impact and between the best environmental erosion control solution and
selection matrices shows that there is often a conflict the desired human use of the area. For instance, vegetation
31

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Estuarine Shoreline Development Handbook
erosion control is in general the preferred option for the
environment in areas where it will work, but a vegetated
shoreline precludes intensive use of the shoreline for
walking, swimming, boating, etc. By combining two or
more shoreline erosion control methods, the environmental
benefits of the best methods can be achieved while still
providing the desired human use. This might be done by
using vegetation or a sill with vegetation for most of a
shoreline, but then providing a small swimming beach
confined by groins or breakwaters. A beach can also
provide a shoreline suitable for landing small boats,
walking, etc.
A combined method may also be the best option when
there are a variety of shoreline types in a single area or
when one portion of the shoreline requires substantial wave
protection because of adjacent structures, while other areas
of the same shoreline can be allowed to erode slightly in
major storms. An example is shown in Figure 19.
Figure 19 shows a shoreline where extensive eroding has
been ongoing. At the northern end of the property there is
a series of eroding marsh headlands separated by small
pockets of sand seaward of an eroding bank. The southern
end of the property turns toward the west with a different
exposure. A roadway is threatened by the shore erosion
process.
The figure shows the proposed shoreline erosion control
method. Low sills with sand fill and marsh plantings are
recommended for the northern end of the property. The
sills will stabilize the eroding scarp of the marsh headlands
and also help confine the sand fill within the sand pockets.
Sand fill and marsh plantings will help stabilize the banks
landward of the beach. The marsh grass at the upper slopes
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Estuarine Shoreline Development Handbook
Table 2. Shoreline Development Impact Matrix.
SHORELINE
DEVELOPMENT
Habitat
Loss
Circulation
Effects
Scour and
Sediment
Runoff
Vegetation
Shading
Visual
Impact
Vegetation
•
O
O
•
—
•
Sills and Reefs
O
o

•
—
o
Beach Fill
~

o
—
—
o
Breakwaters
~
o
o
—
—
~
Revetments
~
~
~
¦
—
~
Groins
~
¦
¦
—
—
~
Bulkheads
¦
¦
¦
¦
~
~
Launch Ramps
~
~
~
¦
—
~
Piers and Pilings
—
—
~
—
¦
¦
Mooring Slips
¦
¦
~
—
—
¦
Boat Houses

—
~

¦
¦
MATRIX KEY: #8606110181 Impact
O Minor Benefit
— No Impact
~ Minor Negative Impact
¦ Major Negative Impact
of the beach will help prevent the sand fill from being
carried landward over the existing bank during storm
conditions. A low continuous sill is recommended for the
marsh at the southern end of the project. This sill will
stabilize the erosion of the front edge of the marsh,
preventing additional erosion while preserving the benefits
of a marsh. The sill is low and porous enough that it will
not prevent flooding of the marsh or movement of marine
life into and out of the marsh.
This design is economical, environmentally desirable,
and provides a range of human use alternatives. It
combines marsh vegetation, bank grading, bank vegetation,
and sand fill. All runoff from the roadway is filtered
through sand or vegetation and a large amount of new
marsh is created. Each shoreline must be evaluated based
on the shoreline characteristics, wave and water level
conditions, and needs of the owner; but it is often possible
to combine a number of alternatives to create the optimal
shoreline erosion control plan.
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Estuarine Shoreline Development Handbook
Table 3. Shoreline Human Use Impact Matrix.
SHORELINE
DEVELOPMENT
Boating
Swimming
Fishing
Walking
Viewing
Vegetation
¦
~
~
~
•
Sills and Reefs
¦
~
~
~
•
Beach Fill
•
•
0
•
o
Breakwaters
o
0
•
—
—
Revetments
~
~
o
~
—
Groins
~
0
•
~
—
Bulkheads
•
•
~
o
~
Launch Ramps
•
¦
o
~
¦
Piers and Pilings
•
0
•
~
¦
Mooring Slips
•
~
—
~
~
Boat Houses
•
o
~
~
¦
MATRIX KEY: •Compatible
O Somewhat Compatible
— No Impact
~ Somewhat Not Compatible
¦ Not Compatible
PROFESSIONAL GUIDANCE
Minimizing the environmental effects of shoreline
development can be complex, with a wide variety of factors
entering into each shoreline erosion control or shoreline
access plan. It will generally be beneficial to obtain
guidance from experts in the field. Assistance can be
provided by governmental agencies involved in protecting
the environment and providing permits for shoreline
development. This includes U.S. Government agencies
such as the Environmental Protection Agency, the Army
Corps of Engineers, and the Fish and Wildlife Service;
State departments such as the appropriate environmental
protection agency and natural resource agency; and local
departments such as city or county permitting, planning,
and zoning agencies.
All construction in estuarine waters will require a
permit, and obtaining information on local requirements
before planning is complete can save considerable time due
to plan revisions and adjustments. Coastal engineers,
environmental consultants, experts from local universities,
and local contractors can all provide information based on
local knowledge and experience.
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Estuarine Shoreline Development Handbook
Table 4. Shoreline Erosion Control Applicability Matrix.
SHORELINE EROSION
CONTROL TYPE
Marshes
Beaches
Low Banks
High Banks
Bluffs
Vegetation
•
O
—
—
—
Sills and Reefs
0
—
—
—
—
Beach Fill
~
•
—
~
~
Breakwaters
—
•
o
0
—
Revetments
~
—
•
•
•
Groins
¦
•
—
—
~
Bulkheads
¦
~
•
o
—
Drainage Controls
¦
~
—
o
•
Slope Flattening
¦
¦
o
•
—
Relocation
—
—
—
—
—
No Action
n
~
n
~
~
MATRIX KEY: 9 Almost Always Applicable
O Usually
— Sometimes
~ Rarely
¦ Almost Never Applicable
Table 5. Shoreline Erosion Control Selection Matrix.
SHORELINE EROSION
CONTROL TYPE
Fetch Length
Water Level
Wave Length
Relative Cost
Vegetation
< 1 Mile
Any
Any
Low
Sills and Reefs
<5 Miles
Any
Any
Low
Beach Fill
Any
Medium
Low
Moderate
Breakwaters
Any
Any
Any
High
Revetments
Any
Any
Any
High
Groins
Any
Any
Low
Moderate
Bulkheads
Any
Medium
Any
High
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Estuarine Shoreline Development Handbook

Figure 19. Plan View of a Sample Shore Erosion Control Project.
36
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Estuarine Shoreline Development Handbook
6.0 APPENDIX: ADDITIONAL INFORMATION
Bellis, Vincent, et al., "Estuarine Shoreline Erosion of the Albemarle-Pamlico Region of North Carolina," North Carolina
University Sea Grant, 1975.
Boesch, D.F., "Conference on Coastal Erosion and Wetland Modification in Louisiana," U.S. Fish and Wildlife Office
of Biological Services, September 1982.
California Department of Boating and Waterways, "Layout, Design and Construction Handbook for Small Craft Boat
Launching Facilities," March 1991.
Canning, D.J., "Marine Shoreline Erosion: Structural Property Protection Methods," Washington Department of Ecology
Shorelands Tech. Adv. No. 1, Ver.2, January 1991.
Canning, D.J., "Shoreline Bluff and Slope Stability: Management Options," Washington Department of Ecology
Shorelands Technical Advisory Paper No. 2, Version 2.0, Mar. 1991.
Clark, John, "Coastal Ecosystems, Ecological Considerations for Management of the Coastal Zone," The Conservation
Foundation, 1974.
Collier, Courtland, "Seawall and Revetment Effectiveness, Cost and Construction," State University of Florida Seagrant,
1975 (FLSGP-T-75-002).
Combe, A.J., et al., "Shoreline Erosion: Control Demonstration Program, Revisited (Final Report)," Office of the Chief
of Engineers, 1989 (NTIS PB91-141598/XAB).
Duke University Press, "Living With the East Florida Shore," 1984.
Fish and Wildlife Service Biological Services Program, "Biological Impacts of Minor Shoreline Structures on the Coastal
Environment: State of the Art Review," Prepared by Beak Consultants, Inc., Portland, OR, March 1980.
Fulton-Bennett, Kim and G.B. Griggs, "Coastal Protection Structures and Their Effectiveness," University of California
at Santa Cruz, no date.
Harris, J., "Study to Determine the Impact of Landward Bulkheads or Alternative Structures on Marshes: Summary
Report," Engineering Science, McLean Virginia, 1981.
Knutson, P.L., and H.H. Allen, "Guidelines for Vegetative Erosion Control on Wave-Impacted Coastal Dredged Material
Sites," WES Environmental Laboratory, 1990 (WES/TR/D-90-13), (NTIS AD-A230 267/7/XAB).
Kuo, C.Y., and T.M. Younos, Editors, "Effects of Upland and Shoreline Land Use on the Chesapeake Bay," Proceeding
of the Chesapeake Bay Research Conference, March 1986 (VSG-86-52R).
Mote Marine Laboratory, "Action Plan Demonstration Project for Seawall Habitat Enhancement," Task Statement, 1991.
North Carolina State Sea Grant, "Coastal Development and Areas of Environmental Concern," no date.
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Estuarine Shoreline Development Handbook
North Carolina University Sea Grant, "Planting Marsh Grasses for Erosion Control," 1981 (UNC-SG-81-09).
North Carolina Sea Grant Program, "A Homeowner's Guide to Estuarine Bulkheads," (UNC-SG-81-11), 1981.
Penny, M.E., "Environmental Impact Assessment of Shoreline Bulkheading: A Historical Approach," University of
Rhode Island, Dept. of Geography and Marine Affairs, 1979.
Rogers, Spencer, "Artificial Seaweed for Shoreline Erosion Control," University of North Carolina Sea Grant, 1986
(NCU-T-86-005).
Sarasota Bay National Estuary Program, Fact Sheets, 1992.
Scott, J.W., "Management of Vegetation on Shoreline Sites," Washington State Department of Ecology, Preliminary
Draft, October 1991.
Scott, J.W., "Shoreline Property Owners Guide to Erosion Control and Bank Stabilization with Vegetation," Washington
State Department of Ecology, Preliminary Draft, October 1991.
South Carolina Sea Grant Consortium, "South Carolina Estuaries: Under Siege?" Proceedings of A Conference, December
1988 (SC-SG-PR-88-01).
South Carolina Sea Grant Consortium, "Wealth? or Wastelands? South Carolina's Freshwater Wetlands," Proceedings
of the South Carolina Sea Grant Consortium's Seventh Annual Winter Conference, December 1988 (SC-SG-PR-89-01).
South Carolina Sea Grant Consortium, "South Carolina Coastal Wetland. Impoundments: Ecological Characterization,
Management, Status, and Use," Edited by M. Richard DeVoe and D.S. Baughman, Volumes I, II and III, 1986 (SC-
SG-TR-86-1,2 & 3).
South Carolina Sea Grant, "The Effects of Dredging Salt Marsh Creeks," March 1981 (SCSG-TR-81-05).
State of Mississippi Department of Wildlife, Fisheries and Parks, "Marine Construction Standards for Shoreline Erosion
Control and Shorefront Access Facilities," Prepared by Offshore and Coastal Technologies, Inc., September 1991.
State University of Florida Sea Grant, "Artificial Reef and Beach Erosion Control," 1977 (FLSGP-Z-77-045).
Stickney, R.R., "Estuarine Ecology of the Southeastern U.S.," Texas A&M Press, 1984.
U.S. Army Corps of Engineers, "Low Cost Shore Protection", 1981.
U.S. Army Corps of Engineers, "Low Cost Shore Protection, A Guide for Engineers and Contractors," 1981.
U.S. Army Corps of Engineers, "Shore Protection Manual," Coastal Engineering Research Center, Volumes I and II,
1984.
University of Wisconsin Sea Grant Institute, "Coastal Processes Workbook," (WIS-SG-87-431), 1987.
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