Seafloor change along the Louisiana barrier island coast from the 1930's to the 1980's shows historical patterns of seafloor erosion and accretion. This base of information will be used to evaluate the contribution of catastrophic events to the long-term evolution of this coastal area. USGS scientists have assembled bathymetric surveys from data from the 1880's, the 1930's, and the late 1980's, and are in the process of assembling a similar survey in 1993 following the passage of Hurricane Andrew. The pattern of long-term, large-scale bathymetric change is key information in determining the processes of barrier island evolution and in formulating predictions of future changes. For example, historical data over the past 100 years indicate that the shoreline at Bayou Lafourche has eroded back about 3 kilometers. The USGS, in cooperation with Louisiana State University, documented the long-term historical record of bathymetric and shoreline change along the Louisiana coast. Geological Survey (USGS) studies collect information critical for improved predictions of long-term erosion rates. This information has been used by State agencies within Louisiana to evaluate the cost/benefit ratio for barrier island restoration projects. Simulations of coastal waves quantify the wave-shielding properties of barrier islands. Because these wetlands are nurseries for many species of fish and shellfish, the loss of the barrier islands and the accelerated loss of the protected wetlands may have a profound impact in the billion dollar per year fishing industry supported by Louisiana's fragile coastal environment. Through the processes of increasing wave attack, salinity intrusion, storm surge, tidal range, and sediment transport, removal of the barrier islands may significantly accelerate deterioration of wetlands that have already experienced the greatest areal losses in the U.S. As the islands disintegrate, the vast system of sheltered wetlands along Louisiana's delta plain are exposed to increasingly open Gulf conditions. Although there is little human habitation on these islands, their erosion may have a severe impact on the environment landward of the barriers. Louisiana's barrier islands are eroding so quickly that according to some estimates they will disappear by the end of this century. Geological Survey The environmental consequences of coastal erosion in Louisiana may be severe. Geological Survey show that other coastal processes, such as the longshore redistribution of sediments, are responsible for this erosion." Though it has long been assumed that this erosion was due to the area's rapid rate of relative sea level rise, recent studies by the U.S. In places up to 100 feet of shoreline are disappearing every year. "The barrier islands of Louisiana are eroding at an extreme rate. Louisiana Barrier Islands: A Vanishing Resource - USGS Fact SheetĬoastal and Marine Geology Program> Louisiana Barrier Islands: A Vanishing Resource Louisiana Barrier Islands: A Vanishing Resource USGS Fact Sheet
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