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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

Summary
Introduction
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:
Introduction
Transportation
Coastal Construction
River Modification
Hydrocarbon & Groundwater Extraction
Climate Alteration
Coastal Excavation
Wetland Losses
Acknowledgments
References

Physical Agents of Land Loss: Sediment Budget

Changes in Sediment Supply

Several thousand years ago the principal suppliers of sediment to most non-cliffed coasts were either rivers that delivered sand directly to the beach or nearshore currents that transported sand onshore from the continental shelf. Once at the coastline the sand was redistributed by alongshore currents. The presence of sandy beach-ridges and barrier islands on both Atlantic and Gulf coasts indicate that sand supply was plentiful and beaches were building seaward as sea level approached its current position several thousand years ago. Since then, sediment supplied by some coastal rivers and the continental shelf has naturally diminished as a result of climatic changes and adjustments of the inner shelf profile. Humans have also contributed significantly to the deficit in sediment supply by damming rivers, building seawalls, groins, and jetties, and dredging tidal inlets. These natural and artificial reductions in coastal sediment supply have resulted in the erosion of many beaches, barrier islands, and deltas. Today the only remaining source of sediment for many coastal compartments is local erosion of nearby beaches and bluffs.

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


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