ABSTRACT

Historical monitoring of Mississippi's barrier islands (Petit Bois, Horn, Ship, and Cat) records the direction and magnitude of shoreline change. Long-term shoreline monitoring involves repetitive sequential mapping of shoreline positions using vintage coastal topographic charts and aerial photographs. The mapped results give insight to the natural and artificial trends in sediment movement and deposition. The long-term trends averaged over a 125 year time period (1847--1973) indicate maximum rates of accretion (16 to 125 feet per year) that were generally recorded on the western ends of the islands and maximum rates of erosion (44 to 322 feet per year) that occurred on the eastern ends of the islands. The main process involved is the east-west littoral drift movement. Generally the Gulf facing shorelines experienced higher rates of erosion and accretion than the sound facing shoreline. The one major exception to the east-west changes in the sediment movement is along a north-south trending spit on the most westerly island (Cat Island).

The major factors affecting shoreline changes are fluctuations in sediment supply, high frequency of tropical storms, and artificial change in east-west littoral drift by dredged channels.

The shoreline change study indicates both the long-term effect of tropical storms and significance of the short-term erosional changes and recovery phase of each storm event.

The net loss of land during the 125-year time period was 1800 acres or 18 percent. A majority of processes causing these losses are natural but have been affected by man's influence.

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