Barrier Island Erosion and Protection in Louisiana: A Coastal Geomorphological Perspective

Shea Penland, John R. Suter

Louisiana has the highest rates of coastal erosion and land loss in the United States. In Louisiana, rates of coastal land loss exceed 100 km²/year. Louisiana's barrier islands, whose presence creates and maintains an extensive estuarine system and protects the marshes from the wave energy of the open Gulf of Mexico, are rapidly vanishing, decreasing in area and migrating landward at rates up to 20 m/year. Between 1890 and 1979, Louisiana barriers decreased in area by 37%, shrinking from 92 to 58 km². The life expectancy of individual barrier island systems ranges between 50 years for the Isles Dernieres and 225 years for the Chandeleur Islands. Disappearance of the barrier islands will result in destruction of the barrier-built estuaries and acceler ted marsh deterioration. Such destruction will severely impact the fishery and fur industries, valued at an estimated $1 billion per year, whose harvests depend on the habitat provided by these fragile coastal ecosystems.

Understanding the geological processes, both natural and human-induced, that control barrier island erosion, estuarine deterioration, and marsh loss in the Mississippi River delta plain is essential in evaluating the performance of the various coastal protection methods currently envisioned or being employed. Previous attempts at coastal preservation and marsh management have shown that an integrated approach that enhances natural processes rather than combats them is the most effective. Highways are built with regularly scheduled maintenance programs in mind, and this same concept should be applied to the coastal zone. Preservation of our coastal environments requires a dynamic landscape-maintenance program of regularly scheduled beach nourishment, barrier restoration, fluvial sedime t and freshwater diversions, and revegetation projects.

AAPG Search and Discovery Article #91036©1988 GCAGS and SEPM Gulf Coast Section Meeting; New Orleans, Louisiana, 19-21 October 1988.