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Coastal & Marine Geology Program > National Assessment of Coastal Change Hazards > Open File Report 03-337

An Overview of Coastal Land Loss: With Emphasis on the Southeastern United States

USGS Open File Report 03-337

by: Robert A. Morton

Physical Agents of Land Loss:
Waves, Currents, & Storm Surges
Landslides & Cliff Retreat
Sediment Budget
Relative Sea Level
Climate & Land Loss
Role of Shoreline Characteristics:
Composition, Induration, & Saturation
Coastal Morphology & Vegetation
Role of Human Activities:
Coastal Construction
River Modification
Hydrocarbon & Groundwater Extraction
Climate Alteration
Coastal Excavation
Wetland Losses

Climate & Land Loss

Seasonal temperatures and annual precipitation indirectly influence land loss of both rocky and sedimentary shores. In New England and along the northern Pacific coast, water repeatedly frozen and thawed along fractures and bedding planes causes ice wedging of exposed sea cliffs, and prolonged thawing of permafrost promotes loss of tundra in Alaska. On the other hand, colder climate can also reduce beach retreat during the winter when sea ice forms along beaches and acts as a buffer. The beach itself can also freeze providing additional protection from wave action. Even erosion of unconsolidated bluffs is temporarily halted when the bluffs are frozen, which is a major factor controlling bluff retreat in Alaska and around the Great Lakes. Along much of the Bering Sea and Arctic Ocean coast of Alaska, the sea is covered by ice more than half of the year, reducing the annual rates of shoreline retreat.

Climate can also indirectly influence land loss by affecting the health of coastal vegetation. Vegetation weakened or killed by droughts is less resistant to wave attack than healthy vegetation, and lowered water tables during droughts expose more dry sand, which is more easily removed from beaches by wind. Furthermore, drought-related grass fires can enhance both inundation and erosion rates of wetlands.

Coastal & Marine Geology Program > National Assessment of Coastal Change Hazards > Open File Report 03-337

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