Marine construction standard for shoreline erosion control and shorefront access facilities for the State of Mississippi, Department of Wildlife, Fisheries and Parks

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

State of Mississippi

MARINE CONSTRUCTION STANDARDS

FOR SHORELINE EROSION CONTROL AND

SHOREFRONT ACCESS FACILITIES

Department of Wildlife, Fisheries and Parks

Bureau of Marine Resources

State of Mississippi

MARINE CONSTRUCTION STANDARDS
FO SHORELINE EROSION CONTROL AND
SHOREFRONT ACCESS FACILITIES

September 1991

OFFSHORE & COASTAL TECHNOLOGIES, INC.
P.O. Box 1679
Z7@ Vicksburg, Mississippi 39181

for

STATE OF MISSISSIPPI

Department of Wildlife, Fisheries and Parks

Bureau of marine Resources
2620 Beach Boulevard
Biloxi, Mississippi 39531

This document was f unded in part through a
federal grant administered by the Office of
@@Om

Ocean and Coastal Resource Management under
provisions of the Coastal Zone Management
Act of 1972, as amended.

The State of Mississippi Department
of Wildlife, Fisheries and Parks
presents this information as a public
service. Inclusion of any shoreline
erosion control or shorefront access
method does not necessarily consti-
tute a recommendation, nor is it a
guarantee that any particular method
will be successful for a specific
application.

TABLE OF CONTENTS

PURPOSE . . . . . . . . . .. . . . . . . 1

GENERAL DESIGN . . . . . . . . . . . . . 2
Design Considerations . . . . . . . 2
Design Methodology . . . . . . . . 10

SHORELINE EROSION CONTROL STRUCTURES . . 11

Description of Shorelines . . . . . 11
Shore Protection Methods . . . . . . 12
Impacts of Various Erosion
Control Structures . . . . . . . . 14
Specific Design Recommendations 16
Bulkheads 16
Revetments 18
Breakwaters 19
Vegetation 22

SHOREFRONT ACCESS FACILITIES . . . . . . 24
Description of Access Facilities. . 24
Specific Design Recommendations . . 25
Small Craft Launch Ramps 25
Piers 29
Berthing Facilities 33
Dredged Boat Slips 36
Boat Houses 37

CONCLUSION . . . . . . . . . . . . . . . 38

REFERENCES . . . . . . . . . . . . . . . 39

PLFRPOSE

The objective of this pamphlet is to present
alternatives for shoreline erosion pro-
tection and shorefront access while
protecting or enhancing coastal habitats.

This set of standards is intended to be
useful in aiding the understanding of
options available to individuals for shore-
line erosion control and shoreline access.

This publication presents an overview of
typical designs for coastal structures,
including shore erosion control structures
and structures associated with shoreline
access. It does not provide a complete
guide for design and construction of these
structures. A variety of sources such as
publications of the U.S. Army Corps of
Engineers can provide additional, more
detailed information on specific design
problems. Coastal Engineers and experienced
local contractors can also help ensure a
successful project. Additional guidance
relating to construction and environmental
considerations can be found in the
Mississippi Coastal Program, also published
by the Mississippi Department of Wildlife,
Fisheries, and Parks.

All persons must obtain authorization for
any project in the tidal waters of the State
of Mississippi from the Mississippi
Department of Wildlife, Fisheries, and Parks
before construction begins. Also, the
Vicksburg or Mobile District Corps of
Engineers should be contacted before
projects are begun in non-tidal waters of
the State.

GENERAL DESIGN

Design Considerations

In designing a structure, numerous decisions
on structure location, height and shape must
be made. The factors most important to
structure design include water levels, wave
heights, and envi'ronmental impacts. Other
considerations include toe protection, soil
properties, filtering, and flank protection.

Water Levels determine 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, typi-
cally around 2 feet in Mississippi, can be
determined from Tide Tables published by the
National Ocean Survey. Storm surge levels
can be determined from local experience or
from Federal Emergency Management Agency
(FEMA) publications. Typical storm tides
range from 4 to 7 f eet in coastal waters.
In extreme hurricanes the storm tide can
reach up to 20 f eet. Most structures in
protected coastal waters have finished
elevations of 3 to 5 feet above mean high
tide, while structures in unprotected areas
reach heights of 7 feet above mean high
tide.

Wave heights can 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 determines the height to which a
shoreline erosion control structure should
be constructed to avoid overtopping and
damage to the back of the structure. Runup
is shown in the figure below.

WAVE RUNUP ELEVATION
WIND GENERATED WAVES WAVE RUNUP

DESIGN WATER LEVEL

STORM SURGE

TIDE LEVEL

Figure 1, Wave Runup
(University of Wisconsin Sea Grant, 1987)

Runup will typically range from equal to the
design wave height for a stone revetment to
twice the wave height for a vertical face
bulkhead.

Typically it is not cost effective to
eliminate all overtopping by building an
extremely tall structure. In many cases it
will 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.

Design Level refers to the level of
protection for which a structure is
designed. For instance, a structure can be
designed to survive a storm which occurs on
the average of once in 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 it's 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.

Toe Protection is armoring in front of a
structure to prevent waves from removing the
sediment and undercutting the structure.
Bulkheads typically require rubble toe
protection, as illustrated in Figure 2.
Stone structures often have additional
material placed at the toe to prevent scour
and damage to the structure.

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

SCOUR AT FILTER
70E CLOTH

Figure 2, Typical Bulkhead Toe Protection
(U.S. Army Corps of Engineers, 1981)

Filtering is generally required if fine
material is to be confined by a structure.
A filter layer can either consist of graded
stone, a synthetic filter fabric, or often
a combination of the two. The ef f ect of
inadequate or no filtering versus a proper
filter design is illustrated in Figure 3.

WITHOUT FILTER WITH FILTER

INIrIAL
POSMON Soil and water posses through ML@LV
gaps between stones
MLW& GRADED
SrONE
J FIL rER

-S-11111 rticies
cannot penetrate
@Ground.oter
filter.
flow
Water east rough
structure

FINAL
POSMON Erosion MLW
MLWV continue SYNrHErIC
FIL rER
cLorH

Synthetic filter cloth

a. n - Water con pass throuith filter
Cloth but soil particles cannot
I
Figure 3, Filtering for Stone Structures
(U.S. Army Corps of Engineers, 1981)

Flank Protection is often required because
many shoreline erosion control structures
are vulnerable to erosion around the end of
the structure, which can lead to failure.
Return sections are recommended during
initial construction, as shown in Figure 4,
although in many cases periodic increases in
the length of the return structure may be
necessary as erosion in adjacent unprotected
areas continues.

@E XIST ING
SH0RELINE BULKHEAD@@
L/ Z., @11 7171-1111-1177@
if X* No XXX

(initial Construction) BREAKING
WAVES

RETREATED
SHOff@_._
BULKHEAD-\
BREAKING@
WAVES (Without Flonk Protection)

RETURN BULKHEAD
WALLS

BREAKING WAVES

(With Flank Protection)
ETURN
WALLS

I A I1 1-11 @ I

Figure 4, Schematic Flank Protection
(U.S. Army Corps of Engineers, 1981)

Soil Properties are important to 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:

Gravel: Difficult driving for sheet piling.
Excellent for stone structures. Not usually
found in Coastal Mississippi except near
rivers.

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. Sheet pile embedments typically
range from 6 to 12 feet. Pile embedments
range from 15 to 30 feet. Embedment lengths
should be evaluated by an experienced
engineer or contractor for suitability for
a particular location and situation.

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. Sheet pile embedments typically range
from 10 to 20 feet. Pile embedments range
from 25 to 40 feet. Embedment lengths
should be evaluated by an experienced

engineer or contractor for suitability for
a particular site.

Organic Soils, Peats: Generally not accept-
able unless piles bear on an underl@Lying
strata. May result in large settlement of
stone structures unless the layer is thin.
These soils usually occur in low lying areas
such as marshes.

Design Methodology

1) For erosion control structures, obtain
cross-sections of . the bank to be protected
at 50 foot intervals, extending from the
upland bank to minus 1 or 2 feet below mean
low water. Reference horizontal measure-
ments. to a local baseline, and vertical
measurements to mean low water.

For offshore access structures, measure
water depths at the estimated location of
the structure.

2) Estimate design water levels (tide plus
storm surge) and potential wave heights to
determine the design wave height for the
site. Check the breaking wave height at the
structure. Use the lesser of the design
wave height and the breaking wave height for
design.

3) For erosion control structures, estimate
the wave runup on the structure. If the
structure will be overtopped, consider using
vegetation or a stone or shell apron behind
the structure to reduce erosion. A certain
level of erosion behind the structure may
have to be accepted during large storm
events.

4) Obtain information on soils in the area
of construction. Based on soils choose an
appropriate design and size of structure.

5) Lay out the structure using the cross-
section survey. Check with the Mississippi
Department of Wildlife, Fisheries and Parks,
Bureau of Marine Resources agency for
environmental limitations on construction
and for information on the permitting
process.

SHORELINE EROSION CONTROL STRUCTURES

There are a variety of publications
regarding shoreline erosion control
available which can provide additional
detail on design methods. Among the most
useful are "Low Cost Shore Protection -A
Guide For Engineers and Contractors" (U.S.
Army Corps of Engineers, 1981) and "Shore
Protection Manual" (CERC, 1984). It is
advised that these sources be reviewed prior
to attempting to design any shoreline
erosion control structure.

Description of Shorelines

Shorelines can consist of a variety of
shoreform. types, each with its own erosion
problems. Different shoreforms call for
different shore erosion control solutions.

Banks are steep shoreforms consisting of
soft erodible material such as clay, sand or
gravel. Bank erosion is typically due to a
combination of seepage of groundwater within
the bank, and erosion by wave action at the
base. The most appropriate erosion
protection may consist of a combination of
a drainage system plus wave erosion
protection such as a revetment at the toe.

Marshes are 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.

Beaches are the most common shoref orm 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. Cutting of f or
interrupting the movement of sediment by
jetties or groins can often have a
detrimental effect to beaches adjacent to
the construction.

Shore Protection Methods

Bulkheads are vertical walls which retain
fill and protect the shoreline behind the
structure from erosion, as shown below.

SHORELINE MODIFICATION
DOCKING STRUCTURE

Figure 5, Typical Uses of Bulkheads
(U.S. Army Corps of Engineers, 1981)

Revetments are sloping erosion control
structures, generally made out of stone laid
over a prepared base including filter cloth
and bedding stone.

Breakwaters provide shoreline erosion con-
trol by reducing the wave height impacting
the shoreline, and by trapping sediment on
the landward side.

Vegetation consists of planting an eroding
area with an appropriate species of erosion
resistant grass, perhaps in conjunction a
low stone sill and minor filling with an
appropriate material such as sand.

Other options which are often used in con-
junction with one or more of the above ero-
sion control techniques include infiltration
and drainage controls and slope flattening.
These actions stabilize banks against
erosion due to flowing water and may be
required even when all erosion due to waves
at the base of the bank is prevented by a
revetment or some other means. Figure 6
shows an example of a well designed shore
protection system incorporating drainage
control, slope flattening, vegetation, and
a revetment.

Adequate Setback of Structures to Avoid
Overloading Bank and Provide Safety
Factor in Case of Bank Collapse

Construct Drain and Grade Surface to
Control Su face Water
Weit-Rooted Vegetation to Reduce Surface Erosion

Regrade to Stable Slope
Provide for Drainage of Water
.1-. from Overtopping Waves

Af Stable Stone Armor

.. . .... Toe
Gravel Underlayer@@'@-. ApProtection
and Filter Cloth

Note; Tie Structure Ends into Adjacent Bank to ar
Minimize Damage f rom Flanking Erosion

Figure 6, Well Designed Shore Protection
(University of Wisconsin Sea Grant, 1987)

Impacts of the Various Erosion Control
Options

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.

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, although relocation can
have detrimental impacts on upland areas in
some instances.

Bulkheads are often the least environ-
mentally acceptable alternative because they
provide no habitat or protected areas for
marine life, increase erosion of the shore-
line, and create access problems to the
shoreline. Bulkheads may be the best alter-
native when some water depth is required at
the shoreline for boating activities.

Revetments of placed stone cause less scour
of the sediment in front of the structure
than do bulkheads, and can provide a habitat
for marine life. Revetments can hinder
access to the shore for recreational
purposes, but they often provide an
excellent permanent shoreline erosion
protection solution when complete erosion
control is required. Revetments can harm
downdrift beaches by removing the supply of
sand which has been nourishing the beaches.

Breakwaters provide an area sheltered from
waves, and beaches built up in the sheltered
area behind the breakwater can provide
enhanced recreational potential.
Breakwaters can hinder circulation and cause
water quality problems, and high structures
may also intrude on the view of the water.
Rubble breakwaters provide habitat for
biota, and they may also provide a sheltered
area where submerged aquatic vegetation will
thrive.

Vegetation generally greatly improves the
natural habitat, but hinders other uses of
the shore because travel through the
plantings must be restricted. Vegetation
must be protected from pedestrian use.

Specific Design Recommendations

Bulkheads

* Bulkheads should not, in general, be used
for shoreline erosion control in situations
where other alternatives will work. This is
because bulkheads do not provide habitat for
marine life, and will often cause scouring
of the shoreline, further damaging the
environment.

* Bulkheads may provide the best solution
when a maximum of upland area is required or
deep water is required at the bank.

When bulkheads are required their impacts
can be reduced by providing a substantial
stone toe. This will protect against toe
scour and provide habitat.

* A typical wooden sheet pile bulkheads is
shown in Figure 7. They will typically be
constructed with 12 to 16 foot long sheets
with 8 to 12 feet embedded into natural
ground, depending on the soil type and
density. Each design should be checked for
stability based on site conditions.

Other typical vertical face bulkheads
f ound in coastal Mississippi are made of
concrete and corrugated aluminum metal
alloys. Heavy duty plastic bulkheads are
beginning to come into use.

* Bulkheads must be built at or above the
mean high tide mark.

* In areas where there is substantial tidal
marsh, vertical face bulkheads should not be
constructed. In these cases, revetment
solutions should be explored.

Marine grade treated lumber should be
used for wooden bulkheads. Use of creosote
treated timber bulkheads is discouraged.

TREATED CAP
GROUND CAPBOARD

j TIMBER LINER
BOLTED TO WALER
1011

GALVANIZED TIE ROD

TIE BACK PILE
AT EACH WALL PILE
TIMBER WALES
BOLTED TO PILES

TONGUE AND GROOVE,"@'.
SHEETING 4

TIMBER
PILE

Figure 7, Wooden Sheet Pile Bulkhead (State
of Maryland, 1982)

Revetments

Revetments are generally suitable f or
protecting high or low banks f rom erosion
when a recreational beach in f ront of the
bank is not required. In some cases beaches
may f orm or remain in f ront of revetments,
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.

Revetments must have toe protection
designed into the structure when it is
constructed on easily eroded material such
as sand. Revetments also must be designed
so that erosion cannot outflank the
structure and cause erosion around the ends
of the structure. This can be done by
either attaching the ends to existing
structures or extending return walls back
into the bank.

* Revetments are most commonly constructed
from stone. If local stone is not
available, other designs such as concrete
armor units, wire gabions, etc. may be more
economical. In many cases manufacturers or
vendors will provide design services.
Concrete rubble revetments should be f ree of
exposed steel, paint or petroleum based
products. Asphalt should not be used as
revetment material. Since revetments are
highly visible, only unifore materials
should be used.

Figure 8 shows some of the design
features of a typical armor stone revetment.

OVERTOPPING
APRON

ARMOR LAYER

MHW

-MLW
TOE
PROTECTION
GRADED STONE
FILTER

Figure 8, Armor Stone Revetment
(U.S. Army Corps of Engineers, 1981)

Breakwaters

Offshore breakwaters are sometimes
suitable when a public recreational beach is
desired and offshore water depths are
shallow. One advantage of offshore
breakwaters is that they allow a portion of
the wave energy to reach the beach,
maintaining some transport of sand along the
shoreline. This helps prevent erosion of
beaches due to blocking sand movement.

Breakwaters which are long compared to
the distance offshore Will tend to
accumulate sediments behind them, extending
the beach offshore. In the extreme case,
the beach will eventually extend all the way

to the breakwater. This may interrupt the
movement of sediment to downdrift beaches
and may also reduce water circulation,
causing water quality problems.

Due to the complexity of positioning
offshore breakwaters, it is recommended that
professional assistance be obtained for
design.

Figure 9 shows an example of a small
armor stone breakwater cross section used in
conjunction with vegetation planting. Stone
sizes should be based on local site
conditions, using Table 1.

CREST I
FLL AND MARSH GRASS ARMOR STONE

.. ...... ML
CORE STONE ....... .............................. .......
FILTER CLOTH
MIN. 3 STONES AT TOE OF SILL

EXISTING GROUND

Figure 9, Armor Stone Breakwater Section,
with Marsh Creation

ESTIMATED WEIGHT CORRECTION CORRECTION FOR

OF ARMOR STONE FOR SLOPE UNIT WEIGHT

WAVE ESTIMATED SLOPE UNIT
HEIGHT WEIGHT WEIGHT
H W wr
(f Ob) (f t/f 0 K I (lb/ft3) K 2

0.5 1 1:2 1.0 120 4.3
1.0 10 1:2@ 0.8 130 2.8
1.5 20 1:3 m on meow-0. 7 135 2.4
2.0 50 1: 3@ 0.6 14o 2.0
2.5 100 1: 4 0.5 145 1.7
3. 0 040bomm- 16 1: 44 0.4 150
3.5 260 1: 5 0.4 155onnolillow-1-3
4.0 390 1: 5% 0.4 160 1.1
4.5 550 1-. 6 0.3 165 1.0
5.0 760 170 0.9
5.5 1000 175 0.8
6.0 1300 180 0.7
6.5 1650 185 0.6
7.0 2100 190 0.6

EXAMPLE

GIVEN: The wave height (H) Is 3.0 feet and the structure
slope is 1 on 3 (1 Vertical on 3 Horizontal) and one
cubic foot of rock weighs 165 lbs (wr)

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

W = 160 lbs x 0.7 x 1.3 145 lbs

TYPICAL UNIT WEIGHTS PER CUBIC FOOT:
CONCRETE 144
GRANITE 165
LIMESTONE 156
0
0
0
00@@

Table 1, Calculation of Armor Stone Weights
(U.S. Army Corps of Engineers, 1981)

Vegetation

The success of vegetation as shoreline
erosion control depends on such factors as
climate, soil properties, wave exposure, and
salinity regimes.

Typically, Gulf Coast marshes include
saltgrass and gulf cordgrass, as well as
smooth cordgrass, saltmeadow cordgrass, and
black needle rush. See Table 2.

* The range of vegetation erosion control
can be extended through the use of
structures such as low breakwater sills, as
shown in Figure 9, which remain permanently
in place, or temporary wooden or brush
fences. These structures reduce the wave
height while the plants become established.

Vegetation should be protected from
pedestrian u'se by fences and signs. Access
paths through the vegetated areas should be
provided to public beaches or other
recreational areas.

PLANTING SPECIFICATIONS FOR GULF COASTS MARSH PLANTS

Type Planting Time Plant Form Spacing Location

Smooth March-May Sprigs 31 apart MLW to
Cordgrass 15 Week 1.51 NNW
6 Month 1.51
or Plugs

SaLtmeadow March-May Sprigs 31 apart NNW to
Cordgrass 15 Week high tide

Gulf March-May Sprigs 1.51-31 NNW &
Cordgrass 15 Week 1.51 above
6 Month 1.51

Salt Grass Spring Seedlings 1.51-31 NNW &
above

Black Spring Seedlings 1-5% of Above NNW
Needle Rush cordgrass
plantings

Common Reed Spring Sprigs 1.51-31 Above NNW

Table 2, Planting Guide for Marsh Plants
(U.S. Army Corps of Engineers, 1981)

SHOREFRONT ACCESS FACILITIES

Description of Access Facilities

This section describes shorefront structures
designed to provide access to coastal
waters. Typical structures most commonly
built in coastal Mississippi include mooring
and fishing piers, boat ramps, dredged boat
slips, boat houses and berthing facilities.

Piers for mooring purposes are usually built
parallel to the shoreline. In cases where
water depth is a factor, piers are
constructed perpendicular to the shore with
boats being moored along side. Commonly
when there is adequate navigation clearance
a 'IT" or "Ll' section is attached to a
perpendicular pier for mooring. Mooring
piers are also used for fishing access and
many pier are used exclusively for fishing
or passive recreation.

Boat ramps for both residential and public
use are very popular in coastal Mississippi.
Most public boat ramps are constructed for
high volume use, while residential boat
ramps are not built to the same degree of
improvement.

Many property owners choose to moor their
boats by creating a boatslip from the upland
portions of their property. In the past,
boatslips were dredged deep into the upland
property creating a square or rectangular
boatslip with upland on three sides. This
type boatslip exhibits poor water quality
conditions because of the lack of water
movement in and out of the boatslip. This
type of boat slip is no longer permitted in
coastal Mississippi. A new type of boatslip

is now being constructed along the coast,
with the slip parallel to the shoreline and
sides angled to allow better water flow
through the boatslip.

Often there is a need to protect moored
boats from the weather. In these cases
boathouses are constructed over the mooring
area. In addition to a weather proof roof,
many boats are hoisted out of the water for
additional protection.

on occasion, individuals and local agencies
desire to provide facilities for the
berthing of many boats. Marinas usually
require extensive planning and professional
assistance. However, some guidance for
berthing facilities is included in this
publication as this guidance can be used for
other applications.

Specific Design Recommendations

Small Craft Launching Facilities

This section describes the design of boat
launching ramps generally used for public
use. Private boat launching ramps will
typically be less elaborate.

* 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
launching lane will handle approximately 50
launchings and 50 retrievals per day.

Launching ramps should have a minimum
slope of 1 (vertical) on 9 (horizontal) and
a maximum slope of 1 on 6. The slope should

be kept constant if possible.

* 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, as shown in Figure 10.
The vertical curve keeps trailer hitches
from striking the launching ramp at a change
in grade, and enhances driver's vision while
backing. A 15 to 20 foot vertical curve is
recommended.

HEM OF RAW

r w
DOM HM WATER

........ .. .................
,F DESM LOW WATER
N TO 2a ... ......
VERMAL CURVE
TOE OF RAMP\

H
Figure 10, Small Boat Launching Ramp
(State of California, 1991)

* Private individual boat launching ramps
will typically be narrower (approximately 15
feet or less) and will not extend as deeply
into the water (generally no deeper than -3
feet MLW) as described here.

Construction Details:
r M",.'
7W@@ V @@E

Concrete should have a minimum of 3
inches of cover over rebar. Concrete should

be a total of 6 inches thick in fresh water
and 8 inches thick in salt water. Minimum
steel reinforcement should be #4 bars at 12
inches both ways, or as required by the
design engineer.

Precast concrete planks should be
designed to bolt, cable, or key together
during installation. Planks should be
placed over geotextile fabric to prevent the
foundation soil from being washed through
the gaps.

In areas subject to undermining from
currents or waves, the ramps must be
protected by a 3 to 5 f oot perimeter of
riprap or other means of protection.

It is recommended that boat ramps be
finished with V-grooves aligned at 60
degrees to the longitudinal axis of the
ramp. The grooves should be 111 by 111. This
is especially important in salt water where
slick marine growth will frequently be
present. spinning tires will quickly wear
away the growth on the peaks of the grooves
to provide traction.

* Private individual boat ramps not using
concrete should use 6 to 8 inches of clean
compact shell, limestone or gravel.

Shoreside Facilities:

* Where possible, parking areas should be
located immediately adjacent to the
launching ramp with all spaces within 600
feet of the ramp.

Garbage receptacles for marine trash

should be provided as close to the launching
ramp as practical.

* A minimum of 20 to 30 car/trailer parking
spaces per launching lane should be
provided. Pull-through trailer spaces are
recommended to the maximum extent possible.

* Car/trailer spaces should be 101 wide by
401 long. Additional car-only spaces should
be provided for picnic, day-use and other
activities in the vicinity of the launching
area.

One handicap parking space should be
provided for every 50 car/trailer spaces and
every 40 single car spaces, with a minimum
of one handicap parking space. Handicap
spaces should be located near the launching
ramp and restroom, and should conform to all
State and local regulations.

No overhead power lines should be
permitted over parking areas, launching ramp
areas, or any other areas where a vehicle
can drive while towing a boat trailer within
the project area, due to the possibility of
trailerable sailboats with metal masts using
the facilities.

Environmental Concerns:

Launching Ramps will not be permitted for
construction in,marsh areas.

* Care in the placement of launching ramps
should be taken to avoid interrupting the
natural movement of beach sand. This may
lead to the buildup of sand on the updrift
side of the ramp and erosion of the beach on
the downdrift side of the ramp.

* Boat Launching Ramps should be located in
areas where there are no underwater
obstructions to interfere with launching or
navigation near the facility.

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.

Piers

All public piers shall be handicapped
accessible with safety rails and wheelchair
guards, and shall be at least 61 wide.

* Piers used for mooring or docking shall
provide a combination of safety rails and
wheel chair guards to accommodate handi-
capped individuals.

Public piers should be lighted.

Piers shall not obstruct 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 in
which they are located. See Figure 11 for
typical pier layouts.

Piling design should be based on local
conditionst including water depth and
geotechnical conditions. Local knowledge
will often be the best guide for small
private facilities. Larger facilities will
require the services of an engineer and a
soils exploration program to determine
required pile sizes and embedment depths.
See Figure 12 for typical pier sections.

PERPENDICULAR 7- PER
TO SHORE

MAXMUM OF V4 WAY
ACROSS WATERWAY (TYPJ

PARALLEL TO SHORE V PIER

Figure 11, Typical Pier Alignments

* Good foundation conditions and moderate
water depths will typically require piles
with embedment lengths of 15 to 30 feet with
butt diameters ranging from 10 to 12 inches
maximum to 6 to 8 inches minimum. Soft
foundation soils will require embedment
lengths ranging from 25 to 40 feet.

Construction Details:

All piers should have railing capable of
withstanding a horizontal force of twenty
pounds per linear foot, applied at the top
of the railing. Top rails should be 4211 in
height and be sloped on a 30 to 40 degree
angle to reduce sitting on the top rail.

* Typical wooden deck planks should be 6 or
8 inches wide and be placed with the heart
side down. Spacing should not be more the
1/411 between deck planks to facilitate
wheelchair use.

* Typical residential piers have pier bents
that range from 61 to 101 apart, with 8 to
12 inch wide cross beams, 6 to 10 inch cross
bracing, and 8 to 12 inch wide deck joists.

Public piers with handicapped access
should have handrails with the top rail 32
inches above the deck on all sloped pier
sections.

Environmental Considerations:

For piers four feet wide or greater,
elevations of the pier deck should be a
minimum of 1 foot above vegetated bottoms
for every 1 foot of pier width, and provide
I inch spacing between decking boards to
prevent the shading of vegetation. Public
piers accessible to the handicapped should
provide turn around areas with 1/4 inch
spacing at ends of piers or every 100 feet.
Minimum turnaround areas shall be 5 feet by
5 feet in dimension.

Pilings -supporting piers should be
concrete or chemically treated in accordance

LIU4T FD(TLFE

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WHEELCHM GUAF0 RAIL CAP
AND MOORNG RAL
SAFETY RAL

DECKNO
BLOCKMNG DECK JC*T$

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--JI
igure 12, Typical Public Pier Cross-
Section MIM, RAL DEICK@
32

with American Wood Preserver's Association
recommendations f or the environment in which
the piling will be placed. Generally, wood
should be treated with 2.5 CCA for saltwater
and .6 CCA for freshwater.

The use of creosote treated lumber is
discouraged.

Berthing Facilitiles

Channels and Fairways:

* Entrance Channels should have a minimum
width of 75 feet at the design depth or
bottom' and a minimum depth of 3 feet below
the anticipated deepest draft vessel or 5
feet, which ever is greater.

* Interior Channels should have a minimum
width of 75 feet at the design depth, and a
minimum depth of 2 feet below the
anticipated deepest draft vessel, or 4 feet,
which ever is greater.

Fairways should have a minimum width of
1.75 times the length of the longest berth
where berths are perpendicular to the
fairway, or a minimum width of 1.5 times the
length of the longest boat where boats are
berthed parallel to the fairway.

* Fairways should have a minimum depth of
6 feet for boats up to 45 feet in length, 8
feet for boats up to 55 feet in length, and
10 feet for sailboats up to 65 feet in
length.

Berths:

* Berths should have the same water depth
as fairways.

It is recommended that berth widths be
provided based on expected boat lengths:

Boat Length Berth Width
201 10,
241 121
281 131
321 141
361 151
4.01 161
501 171

Main walkways should be 6 feet wide.
Finger piers should be a minimum of 2.5 feet
wide up to 20 feet long, 3.0 feet long up to
35 feet long, 4.0 feet wide up to 60 feet
long and 5.0 feet over 60 feet long.

Land Areas:

A minimum of 0.6 parking spaces per
recreational boat berth should be provided.
This is in addition to parking needs for
other areas such as restaurants, public
fishing piers, launching ramps, etc.

* Parking areas should be located such that
no parking space is more than 1,000 feet
from any berth.

* Approximately 2% of all parking spaces,
but not less than one space, shall be
reserved for handicap parking.

* Runoff should be controlled through the
use of grassed swales, detention ponds, or
other filtration methods to protect the

quality of the receiving water.

Services:

All shoreside utilities should be
underground, and should conform to accepted
practice and all applicable codes.

* All utility lines shall be installed so
they are not exposed on the deck of the
structure. For, floating piers, utility
lines should have not less than 6 inches of
clearance above the waterline under dead
load conditions, nor less than 2 inches
clearance under dead load plus live load
conditions.

* All water lines shall be equipped at the
shore end with appropriate anti-siphon
devices.

Fire protection shall be provided in
sufficient locations to afford protection to
all structures and boats in the marina at a
rate of not less than 40 gpm at 40 psi.
marina designers should check with local
fire officials for other requirements for
fire fighting at specific sites.

* It is recommended that circuit breakers
equipped with ground fault interrupters be
provided at all berth power outlets. GFI's
should be tested and maintained at regular
intervals to insure that the devices remain
in working order, especially in a salt water
environment.

A minimum of one shoreside pumpout
installation must be provided at every
marina. This facility should be approved by
the local authority having jurisdiction over
sewage disposal.

Dredged Boat Slips

* Residential boatslips cut into the shore
shall have each side cut at 45 degrees or
less to the shoreline, as shown in Figure
13. The slip width should be based on the
berth widths indicated in the previous
section. Boats should generally be moored
in the boatslip parallel to the shore.

The back side of the boatslip shall be
equal to or slightly longer than the boat
proposed to be moored.

Boatslips shall not be dredged in or
through marsh areas.

BAYOU

4-@
MOOFM Pu a-usTm

45'

Figure 13, Indented Boatslip

Boat Houses

Boat houses should be designed to be
visually unobtrusive. Completely enclosed
structures are discouraged.

Boat houses constructed seaward of the
shoreline should be as near the shoreline as
water depths allow.

Boat houses with motorized boat hoists
should have sufficient structural capacity
to accommodate the boat to be lifted.

* Electrical service to boat houses should
incorporate ground fault interrupters.

ROOF

L
PLE,,, OPr=N SDr=S

MW
HLW

BOTTOM

Figure 14, Boat House Section
L

CONCLUSION

There are a wide range of options available
for controlling shoreline erosion and
providing access to the shoreline without
degrading the natural environment. This
pamphlet presents suggestions, and in some
cases requirements of the State of
Mississippi, which will help provide cost
effective measures which have been proven to
have the least impact on our shorelines.

Individuals planning on constructing
shoreline erosion control or shorefront
access facilities are urged to contact the
State of Mississippi Department of Wildlife,
Fisheries and Parks for guidance before
beginning construction. Engineers and
contractors with local experience can also
be of help in planning a project, obtaining
required permits, and insuring that the
project is properly built.

By taking proper care in planning and
constructing shoreline structures, we can
enjoy our natural resources while preserving
the environment for future generations.

REFERENCES

American Wood Preservers Institute, 11AWPI
Technical Guidelines for Pressure-Treated
Wood", 1970.

CERC (Coastal Engineering Research Center),
"Shore Protection Manual",, Volumes 1 and 2,
U.S. Army Corps of Engineers, 1984.

Quinn, Alonzo, Design and Construction of
Ports and Marine Structures, McGraw-Hill,
N.Y., 1972.

State of California, Department of Boating
and Waterways, "Layout, Design and
Construction Handbook for Small Craft Boat
Launching Facilities", March 1991.

State of California, Department of Boating
and Waterways, "Layout and Design Guidelines
for Small Craft Berthing Facilities",
January 1984.

State of Maryland, Department of Natural
Resources, "An Assessment of Shore Erosion
in Northern Chesapeake Bay", 1982.

State of Mississippi Department of Wildlife,
Fisheries and Parks, "Mississippi Coastal
Programs," 1988, Fourth Printing.

State of Washington, Department of Ecology,
"Shoreline Management Guidebook", 1990.

U.S. Army Corps of Engineers, "Low Cost
Shore Protection - A Guide for Engineers and
Contractors", 1981.

University of Wisconsin Sea Grant Institute,
"Coastal Processes Workbook, 1987.

NOAA COASTAL SERVICES CTR LIBRARY

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