1. United States Coasts
 Atlantic coast
 Pacific coast
 Gulf coast
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2. 1. Atlantic Coast
 Most coasts open to storm wave attack
 Barrier islands common from Massachusetts south
 Bedrock
 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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3. Atlantic Coast
 Strong 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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4. Atlantic Coast
 Barrier islands
 Drowned river
valleys
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5. 2. Gulf Coast
 Low tidal range
 Generally low wave energy
 Tectonically subsiding
 Mississippi 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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6. 3. Pacific Coast
 Tectonically rising
 Experiencing less erosion than Atlantic or Gulf
coasts
 Open exposure to high energy waves
 Average rate of erosion 0.005 meter
(0.016 feet) per year
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7. Stabilization
 Structures built to decrease coastal erosion and
interfere with sand movement
 Also called armoring of the shore
 Often results in unwanted outcomes
 Some structures may increase wave erosion
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8. Stabilization
 Four major types of stabilization structures:
1. Groins and groin fields
2. Jetties
3. Breakwaters
4. Seawalls
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9. 1. Groins and Groin Fields
 Built perpendicular to
the beach
 Often made of rip rap, or
large blocky material
 Traps 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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10. 2. Jetties
 Built perpendicular to shore
 Built in pairs
 Built to protect harbor entrances
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11. 3. Breakwaters
 Built parallel to a shoreline
 Designed to protect harbors from waves
 Can cause excessive erosion, requiring dredging to
keep area stable
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12. Seawalls
 Destructive to environment
 Designed 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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13. Alternatives to Hard Stabilization
Three major alternatives
1. Construction restrictions
2. Beach replenishment
3. Relocation
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14. Alternatives to Hard Stabilization
1. Construction restrictions
 Simplest alternative
 Limit building near shorelines
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15. Alternatives to Hard Stabilization
2. 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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16. Alternatives to hard stabilization
 Relocation
 Move structures rather than protect them in areas
of erosion
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