Puget Sound shore erosion protection study

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

Western Washington University

Project Completion Report

Puget Sound Shore Erosion Protection Study

Contract No. 78-078 Washington

June 30, 1978

Property of CSC Library

The preparation of this report was financially aided through a grant
from the Washington State Department of Ecology with funds obtained
from the United States Department of Commerce and appropriated from
Section 305 of the Coastal Zone Management Act of 1972.

F--
U. S. DEPARTMENT OF COMMERCE NOAA
COASTAL SERVICES CENTER
* 2234 SOUTH HOBSON AVENUE
o0c::, CHARLESTON, SC 29405-2413

rJ~~~C
* (Jg ~~~~~42

ABSTRACT

Erosion around the marine shoreline of Puget Sound is not as severe as

that found along the Pacific Coast, but it does represent a long-term threat

and potentially severe financial loss to individual private property owners.

Continued erosion forces the property owner to take some kind of action to

reduce the loss of his land. Unfortunately, most people understand little

about the specific causes of their erosion problems and appropriate cost

effective actions. Few sources of information are available to the public.

This report explains some of the basic dynamics of shoreline processes in

Puget Sound and illustrates some structural and non-structural methods of

reducing erosion. In addition, an explanation is given of local, state, and

federal agencies that have jurisdiction over the shoreline and permit pro-

grams administered by each.

SHORE PROCESSES AND EROSION
ABATEMENT ALTERNATIVES FOR
PUGET SOUND

* ~~~~~~~~~~~~~~~~~Page
INTRODUCTION I

THE EROSION PROCESS 2

The Sea 2

Waves 2

Currents 3

Tides 3

The Land 5

Beaches 5

Shore Bluffs 6

EROSION PROTECTION TECHNIQUES 8

Non Structural Techniques 8

Setback 8

Vegetation 9

Beach Nourishment 10

Structural Techniques 10

Bulkheads, Seawalls, Revetments 11

Gro ins 11

CASE EXAMPLES 14

EROSION ABATEMENT ADVISE 36

PERMITS AND ASSISTANCE 48

BEACH AND BLUFF EROSION: 52

Signs of a Problem

GLOSSARY OF TERMS 54

* ~~~~~~~~~~~INTRODUCTION

Most everyone who has lived near the shoreline of a large water body

has at one time seen large structures constructed to protect harbors from

waves or to retard the erosion of the shoreline. Where public property is

in danger of erosion damage or loss, the U.S. Army Corps of Engineers is

empowered by the Congress to take protective measures. However, beach

erosion occurs in many areas where the U.S. Army Corps of Engineers is not

empowered to act. Foremost among these areas are shorelines under private

ownership. Approximately 2075 miles of saltwater shoreline are privately

owned in Washington State with about 75 percent of this mileage bordering

Puget Sound and Georgia Strait. It is to these property owners that this

publication is addressed.

While erosion around the marine shoreline of Puget Sound is not so

severe as that found along specific locations of the Pacific coast, it does

represent a long term threat and potentially severe financial loss to the

property owner. Continued erosion pressures the property owner to take some

kind of action to reduce the loss of his land. Unfortunately, most people

understand little about the specific causes of their erosion problems and

appropriate cost of effective actions. Few sources of information are

available to the general public. This publication explains some of the

basic dynamics of shoreline processes in Puget Sount and illustrates some

structural and non-structural methods of reducing coastal erosion. I~n

addition, an explanation is given of agencies that have jurisdiction over

the shoreline and permit programs operated by these agencies.

This guide is not a do-it-yourself blueprint for shore protection, nor

a substitute for professional engineering advice and design. When faced

with an erosion problem, the information herein will help individuals to

make informed decisions about their problem and inform them of available

resources.

THE EROSION PROCESS

Shoreline erosion is a natural process caused by the interaction of

two systems, the sea and coastal rock formations. The sea is driven by a

* ~~complicated system of dynamic forces including winds, astronomical stresses,

temperature and salinity gradients, plus the earth's rotation which individ-

ually or together generate waves, currents and tides. Coastal rock formations

* ~~present an almost infinite variety of layered and non layered, resistant and

non resistant rocks that form banks, bluffs or cliffs along the standard

edge of the land. The constant erosion of these coastal rocks and rocks found

* ~~far inland, whose eroded remains are transported to the sea by rivers, all

lead to the buildup of beaches. However, the energy that leads to the

natural build up of beaches can also cause its erosion, and it is the latter

* ~~that most concerns and affects land owners in the coastal zone.

The Sea

Waves

Wind is the generator of waves at sea. The longer and stronger the

wind blows and the greater the distance (fetch) over which it blows, the

larger and more powerful the waves will be. Waves are measured by their

height, length, and period (fig.la ). Wave height is the vertical distance

from the trough of the wave to its crest. Wave length is the horizontal

distance between two successive wave crests; and period is the number of

*Underlined terms defined in Glossary of Terms

5 ~~~~~~~~~~~~~~~2

seconds it takes two consecutive wave crests to pass a fixed point. In the

* ~~relatively protected waters of Puget Sound, wave period is usually less than

eight seconds. The higher the wave, relative to its length, the more likely

the beach will erode. High steep waves rapidly break upon the shore

* ~~agitating the beach sediment carrying it both along (parallel) the shore

and offshore into deeper water. The net result is a lowering or natural

erosion of the beach.

Currents

Currents -- the movement of water from one place to another -- are

another force affecting the shoreline. Most important is the longshore

current which is generated by waves striking the shoreline at an angle

(fig. lb ). The longshore current, in addition to the swash and backwash

of waves onto the beach, lead to the movement of beach sediment parallel

to the shore known as littoral transport. The prevailing direction of waves

relative to the shoreline determine the net direction of the transport.

Sediment from eroding bluffs or sediment-laden streams, will be carried

along the shore by the littoral current until the current velocity slows

sufficiently to allow suspended material to settle. When sediment is scarce

the littoral current working with breaking waves will carry existing sedi-

ment away from beaches causing erosion. This sediment will eventually be

deposited on another beach or carried into deeper water.

* ~~Tides

The term tide refers to the periodic rising and falling of water levels

caused by the gravitational attraction of the moon and sun. Tides determine

* ~~the level at which waves hit the beach. They are an important factor in

shoreline change when unusually high tides cause coastal flooding or combine

WA1V E
LE n w H

Figure la

Figure lb

9 ~~~~~~~~~~~~~4

with storm waves to cause severe beach and bluff erosion and flooding.

* ~~~~Tides can produce currents which become very strong, especially

through narrow channels. A strong tidal current can sweep sediments from

the littoral zone into or out of bays and channels.

The Land

Beaches

The beach is the first line of defense which protects the land from

wave attack. There are two principal features of the beach which make

it particularly effective in protecting the land. First, it has a sloping

surface which gradually dissipates wave energy as it flows up the slope.

Second, it is made of loose unconsolidated sediment allowing water to soak

into it and change its slope as waves attack. Any man-made interference

with these characteristics will reduce the natural protection of the beach.

Beaches which are exposed to stoniL-generated waves tend to go through

a seasonal change in slope or profile as wave conditions change. Fall and

winter storms cause high steep waves to break on shore. These waves remove

beach sediment storing it in deeper water in the form of offshore bars. This

reduces the amount of sediment on the beach and it becomes lower, narrower

0 ~~and steeper. During the spring and summer, calmer conditions prevail. Waves

striking the shore are low gentle waves. These waves carry the sediment from

the offshore bars back onto the beach, building it back up and making it wider.

0 ~~~~Beach sediment is derived from rivers and from eroding sea cliffs. The

beach may be thought of as a river of sand and gravel moving along the shore.

if the sediment supply from rivers or bluffs is reduced or stopped, beach

erosion is likely to occur. However, if the sediment supply remains stable,

the beach will only change with the seasonal change of wave energy, or due

to exceptional circumstances.

Nothing substitutes for the work a beach performs. it is a natural

defender of the upland from wave attack, the habitat for various types of

marine life and land animals and a zone of high recreational value. Every

attempt should be made to preserve it in its natural state.

Shore Bluffs

Rimming most of the beaches of Puget Sound are steep shore bluffs, some

standing as high as 200 feet or more above the beach. These bluffs are

mainly composed of clays, silts, sands, gravels, and boulders laid down

during the glacial periods thousands of years ago. Beaches primarily are

created from the erosion of these uplands. Sands and gravels fall onto the

beach where they become part of the loose sediment until they are carried

* ~~away by littoral currents. Thus, erosion of sea bluffs is a necessary process

for natural beach maintenance. However, not only waves cause bluff erosion.

Wind, rain, groundwater, and frost also play an important role in loosening

and removing material and bringing it to the beach. The intensity and

importance of each varies with the degree of exposure of the bluff, the

material it is composed of and other topographic and geologic characteristics.

* ~~Many landslides are caused where impermeable clay layers underlie more permeable

surface soils or glacial strata. After long periods of rainfall, groundwater

is unable to penetrate through the silt or clay layer and begins to move

* ~~laterally saturating overlying materials causing debris slides or slumps.

These conditions often weaken the material cohesion of unconsolidated sediments

until they lead to slides and slumps.

* ~~~Property owners should be aware that shore bluffs do erode, some more

rapidly than others and in some instances are very difficult to control by an

individual land owner or whole community. View homes should be constructed

* ~~~well back from the edge of the cliff to reduce the potential threat of

destruction.

EROSION PROTECTION TECHNIQUES

Beaches are dynamic ribbons of sediment that rim most of our uplands.

They erode, accrete and are subject to long term changes of shape and

* ~~volume. Beach processes and responses should be recognized and disturbed

as little as possible by man. Yet, be design or ignorance man often disturbs

the natural processes at the sea-land interface. Ill-advised intrusion may

* ~~well lead to new or increased erosion and induce or accelerate the threat of

property destruction. The purpose of this section is to briefly illustrate

some of the techniques that may be used under optimum circumstances to reduce

* ~~the erosional threat to personal property. However, in some circumstances,

the most prudent action is to do nothing.

Beaches are a resiliant and natural form of protection for the land,

* ~~however the land is also the source of beach sediment! Thus erosion and

accretion are natural processes that continue along our shorelines. Only

where the works of man are threatened near an eroding shoremay these pro-

* ~~cesses develop into a hazard. Once established along a shoreline, man

finds himself in a position of having to consider additional investments to

protect his developments. Measures designed to protect property from erosion

* ~~hazards fall into two general categories: (1) non-structural and (2)

structural. Non-structural techniques are always preferable. Furthermore,

if the erosion problem impacts neighboring properties, it is wise to develop

* ~~a coordinated effort toward erosion control. Cooperation will help to reduce

costs for professional services and materials as well as prevent the use of

a multiplicity of control measures.

Non-Structural Techniques

Construction Setback. The safest measure is to build well back from the

active shore zone or bluff edge. This will allow natural processed to

operate without the interference from or threat to the property owner. It

is difficult to provide a "rule of thumb" setback line that would apply

everywhere. Must Puget Sound cities and counties have minimum shoreline

construction setback limits established. These tmust be consulted prior to

construction. However, most setback lines are minimum standards and may

not be enough to prevent a further erosion threat. Before considering

0 ~~building, it might be wise to ask neighbors about existing erosion problems,

or to consult an engineer or geologist or local government staff for advice.

Most people purchase existing structures and have no say regarding the

0 ~~original sitting decision. If erosion presents a hazard, it would be worth-

while to investigate the costs of moving the structure farther back from the

beach or cliff edge. Many times such action compares favorably in cost to

0 ~~the construction of a bulkhead or similar structure, which might have a

rather short life span.

* ~~~~Vegetation. There is little information available on the potential use

of vegetation to help abate shore erosion. While most vegetation is gener-

ally unable to withstand direct wave attack, it can be successfully used

with other measures to help stabilize beaches or shore bluff slopes. The

rooting and ground coverage provided by various plant species help to reduce

the erosive effects of rain, running water and frost. Mature upright tree

stands reaching the water's edge are an indication that for a period of

perhaps several decades or longer beach recession was low or non existant.

Great care should be taken not to disturb existing vegetation on a

* ~~shore bluff. The existing vegetation is adapted to a particular environment

and plays an important role in the overall stability of the slope. If growing

vegetation must be cleared, it is wise to have roots embedded within the

0 ~~~~~~~~~~~~~~~~9

soil for stability. A local nursery operator or extension agent should be

* ~~consulted when additional plants are desired to help stabilize a shore bluff.

Beach Nourishment. Beaches are very effective in dissipating wave

energy. When maintained, either naturally or artificially, in adequate

dimensions, they afford protection for the adjoining backshore. The placing

of compatible "borrow" material to help maintain a beach is called beach

nourishment. Artificial nourishment directly remedies the basic erosion

problem, which is a deficiency of natural sediment. When conditions are

suitable for artificial nourishment, long reaches of shore may be protected

at a relatively low cost. Furthermore, this method of protection least

disrupts natural physical and biological shore processes. The costs,

benefits, and long term effectiveness of nourishment should be considered

relative to other erosion protection techniques.

Structural Techniques

Any artificial materials placed on a beach to absorb, reflect, or inter-

cept waves or nearshore currents for the purpose of controlling erosion are

considered structural techniques for erosion control. Such installations

should be employed only as a last resort, for they not only intercept natural

* ~~shore processes, but are often high cost and have a high probability of failure.

A wide variety of materials and designs are available. Cost may vary

significantly among the different types of materials and designs. Steel

reinforced concrete is perceived by most people as the ultimate erosion defense.

While this may be true in some cases, it is not necessarily true for all

erosion problems. The unyielding rigidity of concrete placed upon an ever

changing beach with its variety of pressures often spells failure for the

structure. A structure that can withstand wave attack and yet yield to changes

* ~~~~~~~~~~~~10

in the beach profile and pressures from the shore and uplands will likely

serve better.

Bulkheads, Seawalls, and Revetments. These structures are all similar

0 ~~in that they are built against or parallel to the shoreline but are used in

different situations. They may also be alike in shape and generally con-

structed of similar materials such as concrete, rip rap, wood, or steel.

Bulkheads serve as retaining walls to shield the upland from wave scour

and help hold the land from slumping into the water. They are usually

constructed of wood or concrete with footings (base) extending a minimum of

two feet below the level of the beach to a minimum of one foot above maximum

high tide levels.

Seawalls are specifically designed to withstand the full force of heavy

wave attack. They may also serve as retaining walls and in some locations

as docking facilities. They are usually constructed of thick steel rein-

forced concrete with a concave or stairstep face to help rebuff strong wave

attack.

Revetments are the lightest of the three structures. They are not intended

to retain land or fill, but just to protect the shoreline from waves and

currents. They can be constructed of concrete, interlocking blocks, rocks,

(rip rap) or boulders.

* ~~~Groins. Groins are structures placed perpendicular to the shore. Their

purpose is to build or maintain beaches by trapping sediment moving in the

littoral drift. They may be constructed in various configurations using timber,

* ~~steel, concrete, or rock. Groins can be classified as high or low, long or

short, and fixed or adjustable.

These structures can substantially impact natural beach processes and

0 ~~can have severe consequences. While they trap and build beach sediment for

one property, they starve and cause erosion of beaches downdrift. Downdrift

property owners are almost forced to take the same action (fig.2 ). The net

result is a domino-like installation of groins along a given length of beach

and property owners competing with one another for beach sediment. After

careful study along some high energy shoreline environments, groins have

been used successfully with a program of beach nourishment. In Puget Sound,

the use of groins is seldom justified and should be discouraged as a method

of shoreline erosion protection.

.-~~~~~~~~~~~~~~e r. --.o

pr-0~~ ~ per t

0~~~~iue 2

CASE EXANFLES

Many private property owners around Puget Sound are attempting to re-

duce erosional loss of their shorelands by installing structures of one type

* ~~or another. Seven such sites were selected for study and reporting. They

were selected from around Puget Sound and represent a mix of beaches and

structures. These examples are not intended to be used as blueprints, but

* ~~as illustrations of what has been done and what is planned to reduce erosion.

Details of the physical environment, construction designs and materials,

prognosis, and possible improvements are given to lead the reader toward a

* ~~clearer understanding of the problems and prospects of shore erosion abatement.

SHORE PROTECTION STRUCTURES - ANALYSIS OF DESIGN

1. Structure Number: 1

2. Structure Type: Concrete - vertical/recurved bulkhead

3. Location: Birch Bay, Whatcom County

4. Physical Environment

a. Maximum Wave Heights: Moderate 2-3 feet

b. Tides: Extreme Tide Range: - 4.5 to 12.5
Mean Higher High Water: 9.5
Estimated Highest Tide: 12.5

c. Predominant Littoral Drift Direction: S to N

d. Beach Material: Coarse sand and gravel

5. Coastal Hydraulics

The shore erosion problem at this site may be complicated by two
groins which are located several hundred feet to the south. These groins,

constructed about 20 years ago, interrupted the northward transport of
littoral material, could have contributed to a lowering of the beach
profile and erosion in the vicinity of the bulkhead. The bulkhead was
built in response to this shore erosion. Since its construction, the
beach has lowered about 12 inches leaving another 12 inches of material
over the footing. When, or if, these last 12 inches are eroded, ex-
posing the footing, the bulkhead will be in jeopardy of overturning.
However, the recent erosion rate at the study site has slowed consid-
erably, according to the bulkhead owner.

6. Construction Details

Cost: $1,000 (self-constructed)

El. 12.83

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This bulkhead appears adequately strong to resist the level of wave
attack experienced at this site. There are no weepholes to provide
drainage along the base of the structure, but since the backshore is im-
pervious (concrete patio), none are needed. No tiebacks were incorpor-
ated in the bulkhead, a factor which could hasten overturning, should
the beach lower more than 12 inches.

7. Prognosis

The remaining useful life of this structure is probably on the order
of 20 years. If the beach fronting the bulkhead continues to lower,
larger waves will be able to reach the bulkhead without breaking, and
the amount of wave overtopping could increase significantly.

8. Possible Improvements

A 3-foot wide blanket of 20-50 pound rock at the toe would help to
protect the footing from wave scour and reduce the possibility of bulk-
head failure during a severe storm. Periodic placement of a fairly
large quantity of sandy gravel at the bulkhead toe would also be a
possible alternative should the beach lower more than 6 inches.

SHORE PROTECTION STRUCTURES - ANALYSIS OF DESIGN

1. Structure Number: 2

2. Structure Type: Vertical railroad tie bulkhead

3. Location: Sandy Point, Whatcom County

4. Physical Environment

a. Maximum Wave Heights: High 5-6 feet

b. Tides: Extreme Tide Range: -4.5 to 12.5
Mean Higher High Water 9.5
Estimated Highest Tide: 12.5

c. Predominant Littoral Drift Direction: N to S

d. Beach Material: coarse gravel

e. Beach slope: 1:6

5. Coastal Hydraulics

The western portion of Sandy Point is quite exposed to wave action,
especially to the 90+ mile fetch up Georgia Strait. Fortunately, strong,
sustained northwest winds are rare for the only documented occurrence
(29-30 March 1975) caused considerable damage. This storm lasted about
30 hours. Waves driven by 45-knot winds, eroded the beach allowing
large logs to be thrown into several beachfront houses. In an attempt

to preclude a recurrence of this situation, residents along the exposed
portion of the beach constructed bulkheads of varying types, one of
which is the site #2 bulkhead.

6. Construction Details

Cost: $4,000

EL./5.L5

EL. q.5'
EL. e,$'

rip rp
rav�/ _ EL. 7.26'

This bulkhead appears adequately strong to resist the normal level of
wave attack experienced at this site. The riprap toe protection front-
ing the structure is adequate in size, but is subsiding because of a
lack of proper bedding material. A horizontal cable which connects
the railroad ties, probably lends little strength to the structure.
Had tiebacks been attached to the cable every several feet, its useful-
ness would have been much improved. The bulkhead top elevation is suf-
ficient to provide protection from wave overtopping and debris damage,
except in the rare event of an exceptionally high tide occurring simul-
taneously with high winds from the northwest.

7. Prognosis

If the beach fronting this structure remains unchanged, the remain-
ing useful life is estimated to be about 15 years. However, any inter-
ruption of the southward transport of beach material to, or along Sandy
Point, could result in a lowering of the beach and a corresponding in-
crease in the severity of wave attack at the bulkhead.

8. Possible Improvements

The structure could be improved by removing the existing riprap,
placing an 18 inch thick by 8-foot wide blanket of quarry spalls (20-200

pounds) in front of the bulkhead, and then replacing the riprap on the
blanket as close to the bulkhead as possible. This procedure would
significantly reduct the rate of subsidence of the riprap. However,
it should be noted that the recreational and scenic value of the beach
has been lessened by the use of riprap.

SHORE PROTECTION STRUCTURES - ANALYSIS OF DESIGN

1. Structure Number: 3

2. Structure Type: Concrete - vertical bulkhead (failed)

3. Location: Samish Island, Skagit County

4. Physical Environment

a. Maximum Wave Heights

b. Tides: Maximum Tide Range: -4.5 to 11.0
Mean Higher High Water: 8.3
Estimated Highest Tide: 11.0

c. Predominant Littoral Drift Direction: NW to SE

d. Beach Material: Sand and small gravel

e. Beach Slope: 1:8

5. Coastal Hydraulics

This site is exposed to wave attack primarily from the north. The
net transport of beach material is from the northwest to the southeast,
with eroding bluffs approximately 1/4 mile updrift of the site. Erosion
of the beach appears to be a fairly slow process with the beach profile
lowering at a rate of between 0.05 and 0.1 per year. This erosion con-
tributed to, but does not appear to be, directly responsible for failure
of this bulkhead. The primary cause for failure was probably the slump-
ing of the bank which forced the bulkhead outward from behind.

6. Construction Details

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resis the ave ttackexpeience athisste. oweetheblkha

1-1/2-oot o toe sour wich ha occured ovr thelast 0 y e r Iol
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was virtually no freeboard and any additional wave action probably caused
overtopping, adding to the bluff saturation problem.

7. Prognosis

In this case, the lack of bank stabilization appears to be the pri-
mary cause of the bulkhead failure. If no solution is found for the
bank foundation problem, the undestroyed portions of the bulkhead will
probably fail in the near future. With no toe protection, the bank would
be exposed to wave action, and the erosion rate could increase dramatically.

8. Possible Improvements

Solving the bank foundation problem could help to slow the rate of
erosion at this site. Bank stabilization procedures could include re-
sloping to a more stable angle, dewatering, and revegetation. In addition,
a new means of protecting the bank toe should be provided. This could be
a new bulkhead, either timber or concrete, or a revetment of some sort. In
the event of further bank slumping, a "nonrigid" revetment of rock or
gabions might prove less prone to catastrophic failure than a vertical
bulkhead of wood or concrete.

SHORE PROTECTION STRUCTURES - ANALYSIS OF DESIGN

1. Structure Number: 4

2. Structure Type: Railroad Tie - vertical bulkhead

3. Location: Fidalgo Island, Skagit County

4. Physical Environment

a. Maximum Wave Heights: Moderate 2-3 feet

b. Tides: Tide Range: -4.5 to 15.0
Mean Higher High Water: 11.2
Estimated Highest Tide: 15.0

c. Predominant Littoral Drift Direction: W to E

d. Beach Material: Gravel

e. Beach Slope: 1:8

5. Coastal Hydraulics

This site is exposed to wave attack primarily from the south. While
the transport of beach material is not pronounced, a small net movement
from the west to the east is probable. Since the structure at this site
w~as only recently constructed, no accurate measure of the erosion rate is
available. This bulkhead was constructed to protect the bluff toe from
* ~~~wave attack, thus stopping for the time being, the cycle of toe erosion
and slumping typical of coastal bluffs.

6. Construction Details

Cost: $2,500 (self-constructed)

5. 152'

L. 7.Z

* ~~~~This bulkhead is adequately strong to resist the level of wave attack
experienced at this site, but the structure is not designed to retain
the high bluff behind it. The structure top elevation appears to be ade-
quate, but high tides accompanied by moderate wave action may produce
some overtopping. Since no filter material was provided behind the
structure, fine material eroding from the bluff may continue to pass
* ~~~through the bulkhead. As of the inspection date, toe protection rock
has only been provided along the eastern 25 percent of the structure.
This rock is adequately sized but protection of the entire toe should
be completed promptly. No tiebacks were included in this design, but
the structure is only four feet high and, may be adequately strong to
support the back fill behind it. However, a major bluff failure would
* ~~~overturn the bulkhead whether or not tiebacks were used.

5 ~~~~~~~~~~~~~25

7. Prognosis

The useful life of this bulkhead should be at least 15 years, pro-
viding the bluff behind the structure is stabilized, and that the toe
protection is completed. Should more bulkheads be constructed along
the base of the updrift bluff, the beach erosion rate may increase and
some corrective measures may have to be taken.

8. Possible Improvements

The bluff behind the bulkhead should be watched carefully. Drainage
and revegetation of the bluff should be seriously considered. The west-
ern 75 percent of the bulkhead should be provided toe protection as soon
* ~~~as possible, and free-draining gravel and coarse sand should be placed
as a filter behind the structure.

S~~~~~~~~~~~~~2

SHORE PROTECTION STRUCTURES - ANALYSIS OF DESIGN

1. Structure Number: 5

2. Proposed Structure Type: Concrete - vertical/recurved bulkhead (proposed)

3. Location: Nisqually Reach, Thurston County

Bulkhead Site

b. Tides: Tide Range. - 4.5 to 17.0
_--,---- ..�-"- - ___.,

4. Physical Environment

Estimated Highest Tide: 17.0

c. Predominant Littoral Drift Direction: Approximately neutral

d. Beach Material: Sand and gravel

e. Beach Slope: Approximately 1:8

5. Coastal Hydraulics

This site is evenly exposed to wave action from both the north and
south. No net transport of littoral material is obvious. The concave
shape of the shoreline creates a fairly protected beach at this site.
Offshore wave heights of about three feet are probably reduced to less
than 2-1/2 feet before they reach the shoreline, and beach erosion at
this site does not appear to be severe.

6. Construction Details

Cost: $7,000 (estimated)

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Proposed Design

The proposed bulkhead should be sufficiently strong for the wave cli-
* ~~~mate at this site. However, the indicated bulkhead top elevation of 15.5
feet above mean lower low water (+15.5 mllw) is about 1.5 feet below the
maximum estimated tide. At this elevation, the structure would probably
be overtopped at least once annually. Since the proposed bulkhead does
not completely enclose the backshore area and the foundation is ex-
tremely permeable, raising the top elevation by 1.5 feet or more would
* ~~~not insure that the backshore would remain dry. The plans for the pro-
posed work show a backfill behind the bulkhead to an elevation of +14.5
mllw. This elevation probably will be surpassed by several tides each
year. No toe protection is shown in the design plans, and without toe
protection, the 9-inch deep footing is marginal.

* ~~7. Prognosis

This structure will probably do little to protect the backshore prop-
erty from tidal flooding and could add to the problem by allowing the in-
coming tide into the backshore area and then retaining the water as the
tide recedes. In addition, construction of the bulkhead may cause some
* ~~~increased erosion of the beach in the vicinity of the structure toe. The
life of the bulkhead could be 20 years or more, depending on the toe
scour rate and the degree of maintenance provided.

8. Possible Improvements

* ~~~~To provide protection from tidal flooding, the residence at this site
could be raised to an elevation of at least +18 feet mllw. The bulkhead
top elevation should be at least +18 feet also. An alternative solution
would be to raise the residence, and place a berm of gravel and sand be-
tween the residence and the mhhw line. This berm should extend to an
elevation of about 19 feet mllw and would serve as a debris barrier
* ~~~during extreme tides.

SHORE PROTECTION STRUCTURES - ANALYSIS OF DESIGN

1. Structure Number: 6

2. Structure Type: Concrete - vertical/recurved butlkhead(proposed)

3. Location: Dana Passage, Thurston County

Bulkhead Site

4. Physical Environment

a. Maximum Wave Heights: Mild: less than 2 feet

b. Tides: Extreme Tide Range: -4.5 to 17.5
Mean Higher High Water: 14.4
Estimated Highest Tide: 17.5

c. Predominant Littoral Drift Direction: Approximately Neutral

d. Beach Material: Sand, gravel, and cobbles

e. Bluff Geology: The material at this site ranges from clayey
silt exposed on the upper beach to 10 feet of silty sand in the
lower bank, grading into a more silt free sand above. The lower
bank has been severely undercut by wave action in places. The
bank is failing both as relatively small scale debris slides and
as caving slabs of cohesive sand

5. Coastal Hydraulics
This site is exposed to wave attack primarily from the north. Rela-
tively short fetches limit significant wave heights to less than two feet.
Because the shoreline is oriented perpendicular to the predominant direction
of wave approach, there is little net transport of littoral material along
this beach. Erosion problems here are probably a result of ground water
activity causing the bluff of silt and clay to slump. Wave action then
carries the material from the bluff toe.

6. Construction Details
Cost: $7,000 (estimated)

PROPOSED BACKFILL
280 C.Y's * CLEAN SAND
a GRAVEL TRUCKED IN
FROM AN UPLAND SOURCE
EXIST. BANK

i~ ~~~m, n2 O.C.OF PLUMB,
A5 'I' . EL. 18.0

PROPOSED CONC. BLKHD.
4REBAR 2�O.C, HORZ, a.VERT
K~~~~~~~~~~~~~I M..HW 14.4

x41 4' WEEP HOLES 2.5' OC.

Li
I-..,,. - E "L..12.0
LW A% '4t; E.1.06Y'

L 4", -- _l EXIST BEACH

11.5' -I

Proposed Design

The proposed bulkhead is sufficiently strong to resist waves which attack
this site. The purpose of the bulkhead would be to retain the backfill
material and additional bluff material which slumps onto the backfill and
to prevent toe erosion. The top elevation of the bulkhead is satisfactory,
but a footing depth of one foot may be marginal, particularly with no toe
protection. No tiebacks are shown in the design, and with six feet of fill
behind the structure, tiebacks may be desirable. The surface layer of
beach material appears to be underlain by a clay-like material and atten-
tion should be paid to preparing a foundation for the bulkhead.

7. Implications of the Geology to Shore Defense:

Two aspects of the geology and active geologic processes at this site
relate to the design of any shore protection structures. A bulkhead could
easily slide on the surface of the very hard impermeable silt underlying
the gravels. Thus, it would need to be well "keyed" the silt surface but
without disturbing it. Drainage would have to be carefully provided for
as there would have to be no underf low. Secondly, superficial bank fail-
ure will continue but at a slower rate, even after construction. Thus,
the bulkhead will need to perform some retaining wall functions as well
as providing wave protection.

8. Prognosis

The life of this structure will depend primarily on its ability to
resist overturning due to soil pressure. A high saturated bluff of clay
and silt, and a clay-like foundation, will make the construction of a
durable structure extremely difficult. Even if the bulkhead can resist
overturning, the bluff will probably continue to slump until it reaches
a stable slope.

9. Possible Improvements and Alternatives

The proposed desing may have a better chance of success if the follow-
ing measures are incorporated:

* ~~~~a. Use tiebacks

b. Increase footing depth

c. Provide toe protection

* ~~~~d. Provide an adequate foundation

A riprap revetment is an alternative design which, if economically
feasible, would be more flexible and might be less prone to catastrophic
failure. Here again, foundation preparation would be critical. Another
solution, if permits could be obtained, would be to construct an artifi-
* ~~~cial beach of gravel and coarse sand. If graded to a 1:6 slope, such a
beach fill would require about six cubic yards of material per foot of
beach, in addition to the proposed backfill. This type of protection

* ~~~~~~~~~~~~~32

would not be damaged by additional slumping of the bluff, and with
* periodic replenishment, would protect the bluff from wave action.

0
0

0 ~~~~~~~~~~~~33

SHORE PROTECTION STRUCTURES - ANALYSIS OF DESIGN

1. Structure Number: 7

2. Structure Type: None proposed as yet

3. Location: Tulalip Shores, Snohomish County

Erosion Site

4. Physical Environment

a. Maximum Wave Heights: Severe, 3-4 feet

b. Tides: Extreme Tide Range: -4.5 to 14.5
Mean Higher High Water: 11.2
Estimated Highest Tide: 14.5

c. Predominant Littoral Drift Direction: Northwest

d. Beach Material: Sand and gravel

e. Beach Slope: 1:10

f. Bluff Geology: The geology in this general area consises of a
gray silt making up the lower bluff, with the overlying material

largely sand. The upper surface of the silt unit varies from 10
* ~~~~~to 50 feet above high tide. The site in question appears to be
a low place in the surface of this water-perching silt. The
resulting concentration of groundwater was probably responsible
for what appears to be an ancient landslide.

5. Coastal Hydraulics

This site is exposed to heavy wave attack from the south. An effec-
tive fetch of about 6 miles allows the generation of waves in excess of
5 feet high. The relatively shallow beach probably causes the highest
waves to break offshore, and waves striking the bluff toe should be
limited to 3 to 4 feet under most conditions. The predominance of south-
* ~~~erly waves causes the net transport of littoral material to be toward the
northwest. Erosion problems at this site appear to be serious and seem
to result from ground water activity in the bluff combined with wave
action attacking the bluff toe. The bluff is over 100 feet high and
appears to be composed of silt, clay, and sand. Material from the bluff
is deposited at the bluff toe, then removed by wave action.

6. Construction Details

No bulkhead has been constructed recently at this site, and no design
has been proposed.

* ~~~7. Implications of Geology to Erosion Defense

A bulkhead at this site may need special attention to its foundation
design as the disturbed slide materials may well extend into the upper
beach. As ancient landslides may reactivitate, every effort should be
made to prevent groundwater buildup within the slide mass as well as the
* ~~~bank. Prevention of reactivation through drainage control will probably
be much more effective and cheaper than a retaining structure.

8. Prognosis

Based on the location of old bulkhead remains on the beach fronting
* ~~~the bluff, the bluff is eroding at an average rate of about 1/2 foot per
year. With no remedial action, this erosion rate will probably continue
into the foreseeable future.

9. Possible Improvements and Alternatives

* ~~~~Due to the magnitude of the erosion problem at this site, relocation
of the bluff top residences should be given serious consideration. How-
ever, the erosion process might be slowed by protecting the bluff toe
with a riprap revetment or some other structure which would not be
completely destroyed by future slumping of the bluff.

* ~~~~~~~~~~~~~35

EROSION ABATEMENT ADVICE

The abatement of an erosion problem can be achieved only if the

* ~~causes.-are clearly understood. A variety of processes cause the re-

treat of beaches and shore bluffs, which are not obvious to an untrain-

ed person. It is best to seek the opinion of a professional who can

* ~~~pinpoint the causes, and in the longrun save the property owner time

and money.

There are some basic procedures that should be followed to pro-

* ~~~long the life and effectiveness of any erosion abatement method chosen.

A discussion of the various techniques, their advantages and disadvan-

tages follows.

Construction Setback

The best way to avoid a hazard is to move away from it. Cities

and counties bordering the marine waters of Washington state have shore-

line construction setback requirements established in their shoreline

management programs. These agencies must be consulted prior to con-

struction.

The cost and benefits of moving a home back from the shoreline

or bluff edge should be considered. Many times this cost compares

favorably with other protection methods and might provide protection

longer than many structural solutions.

Advantages:

Reduces the threat of structure destruction.

Allows shoreline processes to operate naturally.

* ~~~~~~~~~~~~36

No impacts to neighboring properties.

Preserves recreational and aestetical value of the beach.

Can be accomplished by the individual through contract with a

housemover.

Minimum of permit problems.

Disadvantages:

Does not stop erosion.

Area must be available for relocation.

May reduce arc of shore view from relocated position.

Special skills and equipment required.

Vegetation

Vegetation helps to shelter and bind the soil and substrate from

erosion. Removal without replanting is poor practice, and bare spots

should be planted. Some varieties of plants are better than others

* ~~~for bank stabilization. A local nursery operator, county extension

agent or local office of the Soil Conservation Service should be con-

sulted. If removal of large trees and other large plants is necessary,

* ~~~the roots should be left in the soil to help maintain stability.

Successive plantings first with grasses or ivy, then with shrubs

and trees will help to shelter and bind the soil and substrate for

maximum protection.

Advantages:

Shelters and bind the soil and substrate.

Reduces soil creep and rain erosion.

Self maintained and renewable protection.

* ~~~~~~~~~~~~~37

Disadvantages:

Does not stop erosion at bluff toe.

Growing vegetation may reduce views.

Vegetation may interfere with access.

Has little effect on deep seated slides.

Beach Nourishment

* ~~~~A viable alternative to saving an eroding beach is to artificial-

ly restore it by adding sediment of a similar type. This technique

is not always practical or possible. Major obstacles to many beach

* ~~~nourishment proposals are the acquisition of large quantities of sand

or gravel of suitable type and size and the transportation of this

material to the beach.

* ~~~~The cost of sand or gravel for beach nourishment depends largely

upon the source of the material and the method and distance of trans-

port. A total cost for loading, hauling and spreading at an approximate

* ~~~cost of $2.50 to $3.00 per cu. yd. A rule-of-thumb estimates that for

each one foot of visible recession of the shoreline, the beach has

lost two cubic yards per shoreline foot. Thus, a 100 ft. shoreline

* ~~~that has eroded ten feet would require approximately 2000 cubic yards

material.

Advantages:

* ~~~~Most effective method of dissipating wave energy.

The beach after treatment remains suitable for recreation and

attractive.

* ~~~~Nourishment does not adversely effect downstream beaches.

* ~~~~~~~~~~~~38

Disadvantages:

Beach will likely require additional material.

Cost and accessibility of "borrow" material may be prohibitive.

* ~~~Bulkheads and Seawalls

These structures are similar. They are vertical walls made of

concrete or wood placed on a beach to rebuff wave attack and retain

* ~~~the land behind the structure. These structures are subject to various

hydraulic forces that must be accounted for in their design and strength

of materials.

* ~~~~Seawalls and bulkheads should be constructed sufficiently high

to prevent wave overtopping during extreme tides and footings should

be dug deep into the beach to avert their exposure. In general, the

* ~~~maximum depth of expected scour is roughly equal to the highest break-

ing waves at the site. Maximum storm waves two feet high prescribe

a footing depth of two feet. It is advisiable to go beyond the mini-

* ~~~mum if economically and physically possible. Some wave scour will

occur; however, large rocks placed on the beach in front of the struc-

ture will help to reduce the erosive impacts of wave scour.

* ~~~~A seawall or bulkhead protects only the land behind it or the

beach in front of them. These structures provide no protection to

either up or downcoast areas. The structures may be placed just at

* ~~~the site of erosion or along the entire length of the property. The

ends should be joined to neighboring structures. Where none exist,

wing walls or tie-ins to the adjacent land must be provided to prevent

* ~~~flanking and possible progressive failure from the ends.

Accumulating water and soil pressures soon build behind bulkheads

* ~~~~~~~~~~~~~39

and seawalls. Drainage must be provided to allow groundwater to escape

from the landward side of the wall. This can be facilitated by back-
filling with gravel and by making frequent openings (weep holes) through

the wall near the level of the beach.

Additional strength can be given to the structure through the use

of tie backs. Tie backs anchor the upper part of the wall with steel

cables to logs or other large materials deeply embedded into the beach

or shore bluff (Figure 3 ). These structures are rarely capable of,

or designed for, stopping deep seated landslide activity. They can

help prevent reactivation of former slides however, by preventing the

erosion.

Advantages:

Shields the land from wave scour and undercutting.

Low maintenance if properly constructed.

Disadvantages:

Limits beauty, access and use of beach.

Incompatible with conditions for some forms of natural plant and

animal life.

Complex engineering design.

Construction requires special equipment.

Subject to failure from use of improper materials or design flaws.

costs:

The costs of seawalls and bulkheads vary considerably. The price

is dependent upon the type of materials used, the special equipment re-

quired, and the type of labor. Generally, wooden installations range

from $30 to $50 per linear foot, and concrete $60 or more per linear foot.

* ~~~~~~~~~~Figure 3

* ~~~~~~~~~~~~~~41

Revetments

Revetments are among the least expensive type of protection.

They consist of armor facing of blocks, rocks, or other hard material

placed like a blanket on the natural sloping shore. The revetement

functions as a wave energy dissipator. Since the joints between the

rocks in the revetment facing are usually open and not watertight,

special care must be taken to prevent scour of supporting shore ma-

terial as the returning splash and surface runoff flows back to the

sea. Twelve to eighteen inches of gravel or woven filter mat should

be placed between the natural soil and the revetment. The filter is

designed to retain the solids as water flows through (Figure 4 )

Advantages:

Relatively least expensive (armor) protection.

Constructed of individual units, able to accommodate some settle-

ment and replacement.

Provides a sloping surface and may accommodate some forms of inter-

tidal marine line.

Disadvantages:

The stability of the light armor facing is dependent upon the

strength underlying base material.

If the filter fails, the underlying material is easily lost through

open joints.

Adversely impact the scenic and recreation quality of the beach.

Costs:

Revetments vary significantly in cost, Most of the cost is in-

volved in the transportation and placement of the material. Prices can

S ~~~~~~~~~~~~42

0AR4~-
0/7-Fo /zi vtAz e -

I I .~~Figre
0�~,. B4

( -~~~~~-

Figure 4

* ~~~~~~~~~~~43

range from $30 to $80 per linear foot.

Groins

Groins are long, low finger-like structures that jut out perpen-

dicular to the shore and dissipate or deflect the erosive energy of

longshore currents and waves. Groins may be used to either maintain

a beach with its present profile or build up a beach by trapping

littoral sediments passing along in the surf. The usual result is a

buildup of sediment on the updrift side and consequent erosion on the

downdrift side. While intended to protect the shore, they often cause

shore erosion, especially downdrift from the structure. Many law suits

have been initiated by property owners claiming increased erosion

damage resulting from the installation of a groin. Groins generally

are not necessary for erosion abatement in Puget Sound, and their use

except in very special circumstances is ill-advised.

Advantages;

Quickly trap and impound longshore moving sediments.

Buildup the beach on the updrift side.

Disadvantages:

Shoreline downdrift will experience rapid erosion.

Unsuitable in areas of low littoral sediment transport.

Opens the property owner to legal liabilities to damages suffered

by downdrift property owners.

Costs:

Small groins can be constructed of wood or rock. The former can

be constructed inexpensively but may require the use of a backhoe or

pile driver. A wooden groin may range in price from $10 to $25 per

Summary of Erosion Abatement Techniques

Construction Beach Bulkhead
Setback Vegetation Nourishment Seawall Revetment Groin

Reduces threat Shelters and After use Shield the Least Quick trap
of destruction binds soil beach suitable land from expensive of beach
and substrate for use wave attack sediment
Allows natural Reduces soil Does not Low main- Individual Builds beach
shore processes creep and impact down- tenance units allows on updrift
to operate rain/gulley stream beaches settlement & side
wash replacement
No impact on No impact on
beach life beach life

Does not stop Does not Does not stop Limits Subject to Downdrift
erosion halt erosion access & settling beaches erode
erosion recreational
use of beach
and scenic
view
Area must be Vegetation Cost and ac- Complex Underlying ma- Unsuitable in
available for may reduce cessibility design terial lost low littoral
relocation views of borrow through joints transport areas
material
May reduce Reduces Impacts Special Impacts Legal problems
views access beach life equipment beach may result
needed life
'-
Special moving Subject to Limits recre- Impacts beach
skills failure if ational use of life
improperly beach and sce-
designed nic value
Impacts Limits recreational
beach life use of beach

$3.00 to $5.00 minor $2.50 to wood: $30 to $30 to $80 wood: $10 to $25
o per sq. ft. $3.00 cu. yd. $50 in ft in ft in ft
concrete: $60 concrete:$30 to
to $80 in ft $80 in ft

linear foot, however, the wood will require relatively frequent main-

* ~~tenance. The costs of a rock groin is dependent upon the accessibility

of large rock. Costs may range from $30. to $80. per linear foot.

CONCLUSIONS AND RECOMMENDATIONS

* ~~~~It should be obvious to the reader that the shore is a dynamic envi-

ronment and a basic incompatibility emerges with the installation of rigid

erosion protection structures in this "fluid" environment. A variety of

* ~~~structural alternatives have been presented; however, each has advantages

and disadvantages that must be considered in light of the physical conditions

that prevail at the erosion site. The selection of the most appropriate

* ~~~technique must be based on an assessment of physical conditions, costs,

and accessibility (fig. 5).

* ~~~~~~~~~~Figure 5

Physical Conditions Cost Accessibility

* ~~~Wave heights Materials Materials
Wave direction Installation Installation
Tidal heights (machinery & (machinery)
Littoral drift labor)
Beach & bluff
geology
* ~~~Water run-off
(surface & ground)

Physical conditions vary greatly around Puget Sound. It is therefore

very difficult to recommend any one erosion protection technique above

another without knowing conditions of the site. However, certain gener-

* ~~~~~~~~~~~~45

alizations can be made for three general catagories of shore types found in

* ~~Puget Sound: low beach (no bluff) beach with low bluff (up to 50 feet), and

beach with high bluff (greater than 50 feet). Under all circumstances,

non-structural alternatives stand alone in reducing erosion with the least

* ~~disruption of natural shoreline processes. If for reasons of physical con-

ditions or cost non-structural methods are not appropriate, structural

techniques may be the only recourse.

* ~~~Along the relatively few low sand and gravel beaches in Puget Sound,

log or railroad tie bulkheads of the type shown in case example (2) appear

to be the most effective in terms of cost and service. Installation of

a log or railroad tie bulkhead with necessary footing depth and supports

are relatively inexpensive to install and provide some flexibility to

long and short term beach changes. Furthermore, repairs are relatively

easy to accomplish. Concrete bulkheads are also often used as erosion

protection on low beaches. While some do serve well, many are prone to

failure or require frequent repair as shallow footings are exposed or

* ~~tension cracks appear, severely weakening the structure.

The most common physical type of shore found around Puget Sound is the

gravel and cobble beach backed by a low bluff. Here it is important to

determine the principal cause of erosion which can usually be attributed to

one of two events, undermining by storm waves, or weakening of the bluff

by ground water saturation. If wave erosion is the principal erosion agent,

rip rap or a wooden bulkhead may be installed to check the waves' erosive

power. However, in many cases, the erosion results from groundwater

saturation of bluff strata causing differential pressures resulting in

* ~~~~~~~~~~~~46

debris slides and slumps. Breaking waves simply move the fallen debris

along the beach. An example of this is shown in case example (6). Under

these circumstances, a strong reinforced concrete retaining wall, back-

filled with gravel appears to be the best solution to reducing the erosion.

Frequent "weep holes" through the wall are necessary to prevent water buildup

behind the bulknead.

Lastly, where erosion is occurring to high shore bluffs in excess of

50 feet, as shown in case example (7), the problem is compounded by the

large amounts of debris that fall upon the beach. Any type of retaining

structure would have to be of massive dimensions beyond the financial

capabilities of most individuals. A few actions may be taken: (1) relo-

cation of the home a safe distance from the bluff edge; (2) removal of

groundwater (dewatering) by pumps or the interception of flow; and (3) the

*placement of rip rap at the toe of the bluff to help reduce the force of

breaking waves. All three actions should be taken, but relocation of the

home (if possible) should be given the highest priority.

Regardless of the physical conditions of the site the property

owner should consider all erosion protection options and discuss them

with his local planning or building department representative. They are

most familiar with local conditions and are in the position to provide

information about the range of alternative actions that are permitted.

0 ~~~~~~~~~~~~~47

PERMITS AND ASSISTANCE

Permits

* ~~~~The property owner faced with an erosion problem should first

consult with his local planning or building and codes department be-

fore taking any action. These agencies participate in Washington's

* ~~~Shoreline Management Program which deals with development on marine

and freshwater shorelines of the state. The local agency can advise

the property owner of site information, possible abatement techniques

* ~~~and inform him of legal limitations.

In most cases it is in the property owners best interests to call

a professional geologist or engineer to review the problem. Prof ession-

* ~~~al advice, in the long run, will save time and money. Perhaps the prob-

lem can be solved by employing a non-structural technique. However,

if structural abatement is necessary, appropriate permits must be acquir-

* ~~~ed prior to installation.

The U.S. Army Corps of Engineers is designated by the U.S. Congress

the authority of regulating all dredging, filling, bulkhead and pier

* ~~~construction in the "navigable waters of the U.S." by The Rivers and

Harbors Act of 1899 (USC. 404 Sec. 10). Along the Pacific Coast, "navi-

gable waters of the U.S." are channelward (seaward) of Mean Higher

* i~~lijU-SWater. Thus, the type of permits necessary for the construction

of an erosion defense structure depends on the location of the proposed

structure in relation to the Mean Higher High Water (MHHW) on the beach.

* ~~~If the proposed structure is landward of Mean Higher High Water, permit

approval need only be obtained from the local (city or county) planning

* ~~~~~~~~~~~48

or building and codes department. If, however, the pro-

posed structure is seaward of Mean Higher High Water, approval must

be obtained from the local agency, Department of Fisheries (state) and

the U.S. Army Corps of Engineers (federal).

Accurate definition of the Mean Higher High Water mark requires

a survey. However, one can estimate the location through the use of

tide tables. Another approach is to assume the lowest limit of land

vegetation growth demarcates Mean Higher High Water. However, it should

be noted that some local jurisdictions do not allow the installation of

defense works beyond the toe of the bluff, or on the backshore berm of

a beach.

Assistance

* ~~~~Local Government. A concerned property owner is probably not the

first or only person experiencing an erosion problem in his local area.

The initial step is to discuss the problem with the local city or county

5 ~~~planning or engineering office. They have designated authority over

development along the shoreline of the local jurisdiction through

Washington's Shoreline Management Program. Furthermore, they are

* ~~~familiar with the area and must be contacted to obtain appropriate

installation permits. While these offices may -not be able to provide

specific remedies to an individual erosion problem, they will explain

5 ~~~the range of actions that are legally permitted. Additionally, they

may be able to direct someone to professionals nearby for area speci-

fic information and assistance.

5 ~~~~State Government. Three different state agencies may be of assis-

tance to the citizen with a beach erosion problem. They are the

* ~~~~~~~~~~~~49

Department of Ecology, Shoreiands Division; Department of Natural Re-

sources, Division of Geology and Earth Resources; and the Department

of Fisheries. These Departments are sources of legal, geological and

biological information relating to the shorelines of the state. How-

ever, they will generally not provide direct assistance to property

owners.

Federal Government. The U.S. Army Corps of Engineers is the lead

federal agency dealing with public works projects in and around navi-

gable waters of the United States. This agency is responsible for

major harbor improvements and erosion abatement projects. They are

designated by law to act only in behalf of the U.S. public at large

and not for an individual citizen. However, general information

dealing with erosion problems and permit requirements is available

through the Seattle District Office.

0~~~~~~~~~~~~~5

PROPERTY
OWNER

APPLY

City
Countyv

STATE
AGENCY REVI E

PERMIT

Granted
or
Denied

BEACH AND BLUFF EROSION:
Signs of A Problem

The understanding of bluff and beach processes is academic
unless the knowledge can be applied in a functional way. Early
recognition of erosion before it progresses into a severe problem
is important to its control. The following gives some of the
* ~~~signs of beach and bluff erosion. Be on the lookout for these
signs and, if possible, study small changes in the nature of
your shore bluff or beach over time using photographs or other
means of comparison.

0 ~~~SHORE BLUFF
Type of Geologic Material

-Hard Rock
* ~~~~~~Homogenous rock and gravel embedded in sand and silt
-Layers of gravels, sands, silts, and clays

Evidence of Instability
- Cracks in the soil parallel to bluff edge
* ~~~~~- Bare exposures of soil (slump scars)
- Trees bend or tilted downslope
- Trees with exposed roots at bluff edge
- Masses or recently fallen debris (soil, rock, & vegetation)
at base of the bluff
- Notching at the base of the bluff from wave scour
- Active water flow over the face of the bluff
- Springs emitting water from within the bluff
- Water slowly "weeping" from strata within the bluff

BEACH
- Obvious longterm recession or lowering of the beach
relative to some "fixed" object *
* ~~~~~- Longterin change in the size of beach sediment from
smaller to larger particle sizes

* ~~~~~~~~~~~~52

* ~~~~~- Undercutting and removal of upland vegetation or
beach grasses

MAN MADE STRUCTURE
* ~~~~~- Bulkheads or other erosion defense structures on
neighboring beaches
- Groins on neighboring beaches "trapping"t beach
sediment
* ~~~~~- Cracking or undercutting (exposed footings) of
existing erosion defense structures

*Study your beach relative to some natural or manmade object
such as a boulder on the beach or piling that is fixed or
photograph the same part of your beach each year in mid
or late summer and compare with older photographs

* ~~~~~~~~~~~~53

GLOSSARY OF TERMS

Backshore: The zone of the beach profile extending landward from the sloping
0 ~~~foreshore to the point of development of vegetation or a change in
physiography (bluff or dunes).

Beach: The zone of unconsolidated sediment extending shoreward from near
low tide line to some physiographic change such as a bluff or dune
field or to a point where permanent vegetation is established.

Beach Nourishment: The process of replenishing a beach. It may be brought
about naturally, or artificially by the deposition of materials from
another source.

Beach Profile: The intersection of the ground surface with a vertical plane;
may extend from the top of the dune line to the seaward limit of sand
movement.

Bluff: A high steep bank at the seaward edge of the coast.

Debris Slide: An unconsolidated mixture of fallen bluff material, vegetation,
0 ~~~and water.

Dewatering: The process of removing ground water by pumping or injecting
pipes to intercept flow.

Fetch: The horizontal distance over which wind generates waves.

Footings: An enlargement at the lower end of a wall or column to distribute
the load.

Groin: A shore erosion protection structure built perpendicular to the shore-
line to trap littoral drift.

Longshore Current: The littoral current in the breaker zone moving essentially
parallel to the shore, generated by waves breaking at an angle to the shore.

Littoral Transport: The movement of littoral drift in the littoral zone by
* ~~~waves and currents.

Littoral Drift: The sedimentary material moved in the littoral zone under
the influence of waves and currents.

Mean Higher High Water: The average height of the higher high water over a
* ~~~19 year period.

Nearshore: An indefinite zone extending seaward from the shoreline to just
beyond the breaker zone.

Offshore: The comparatively flat portion of the beach extending seaward from
* ~~~beyond the breaker zone to the continental shelf.

Revetment: A facing of stone or concrete built to protect a bluff or bank
against wave scour or currents.

* ~~~~~~~~~~~~54

Rip Rap: A layer or facing of stones randomly placed to prevent erosion of
a beach or bluff face.

* ~~Seawall: A structure separating land and water areas, primarily designed
to prevent erosion due to wave action.

Setback: A minimum construction limit near the shore of bluff edge to help
reduce the immediate and future threat of erosion damage.

* ~~Slump: Movement of earth down slope along internal slip surfaces, generally
concave upward.