Mississippi-Alabama: Natural and Man-Made Shores—A Study in Contrasts

by Ervin G. Otvos, Gulf Coast Research Lab, Ocean Springs, United States,

Document Type: Proceeding Paper

Part of: Coastal Zone '93


Quaternary formations essentially define the present configuration of the Alabama-Mississippi coast. As the result of the coast's tectonic history, they are much less widespread and thinner than in the adjacent Louisiana-Texas or the Carolinas-Georgia coastal plains. High sea level Sangamonian alluvium and barrier ridges dominate coastal morphology. Contrary to a common misconception, the present barrier islands did not, as a rule, shift landward with the Holocene transgression. After Holocene sea level rise slowed, the submerged nearshore shoal area about to be occupied by the islands, developed in the path of abundant nearshore sand transport. The Late Holocene barriers formed approximately at their present locations on these shoals. Subsequent development, ongoing subsidence and destruction of Mississippi subdeltas profoundly influenced the development of SW Mississippi marshlands and barrier islands, as well as their subsequent degradation. In combination with recurring tropical storms, large-scale coastal development since the 1920s in Mississippi, in Alabama since the 1970s, created significant erosion and associated land-use problems. One of the most intensively maintained shores anywhere, the minimum energy 40-km Harrison County beach since 1951 has received a total sand nourishment of nearly seven million cubic meters from offshore trenches. In contrast, Alabama Gulf beaches have been much less effected by restoration measures. Tectonic subsidence will continue to aggravate coastal erosion and land loss along the Louisiana border.

Subject Headings: Land subsidence | Coastal management | Islands | Barrier islands | Sand (hydraulic) | Erosion | Coastal plains | Sea level | United States | Mississippi | Alabama | Louisiana

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