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United States CoastsAtlantic coastPacific coastGulf coast

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1. Atlantic CoastMost coasts open to storm wave attackBarrier islands common from Massachusetts

southBedrock

Florida bedrock is resistant limestone.Northward through New Jersey is comprised of

easily erodable recent deposits.New York through Maine has glacier-affected

rocks.

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Atlantic CoastStrong storms called nor’easters can damage

the coast north of Cape Hatteras, NC.Nor’easters can generate storm waves

up to 6 meters (20 feet).

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Atlantic Coast

Barrier islandsDrowned river

valleys

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2. Gulf CoastLow tidal rangeGenerally low wave energyTectonically subsidingMississippi delta dominates

Locally sea level rises due to compaction of delta sediments

Average rate of erosion is 1.8 meters (6 feet) per year

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3. Pacific CoastTectonically risingExperiencing less erosion than Atlantic

or Gulf coastsOpen exposure to high energy wavesAverage rate of erosion 0.005 meter

(0.016 feet) per year

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StabilizationStructures built to decrease coastal erosion

and interfere with sand movementAlso called armoring of the shoreOften results in unwanted outcomes

Some structures may increase wave erosion

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StabilizationFour major types of stabilization structures:

1. Groins and groin fields2. Jetties3. Breakwaters4. Seawalls

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1. Groins and Groin FieldsBuilt perpendicular to

the beachOften made of rip rap,

or large blocky materialTraps sand upcoast,

which can cause erosion downstream of the longshore current

May necessitate a groin field, or a series of groins built along a beach

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2. JettiesBuilt perpendicular to shoreBuilt in pairsBuilt to protect harbor entrances

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3. BreakwatersBuilt parallel to a shorelineDesigned to protect harbors from wavesCan cause excessive erosion, requiring

dredging to keep area stable

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SeawallsDestructive to

environmentDesigned to armor

coastline and protect human developments

One large storm can remove beach

Wave activity eventually undermines seawall structure; need continual repair or will collapse

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Alternatives to Hard StabilizationThree major alternatives

1. Construction restrictions2. Beach replenishment3. Relocation

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Alternatives to Hard Stabilization1. Construction restrictions

Simplest alternativeLimit building near shorelines

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Alternatives to Hard Stabilization2. Beach replenishment

Sand added to beach/longshore current

Expensive; costs between $5 and $10 per cubic yard

Sand must be dredged from elsewhere.

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Alternatives to hard stabilization

RelocationMove structures rather than protect them in

areas of erosion