Geomorphic classification of coastal land loss between 1932 and 1990 in the Mississippi River delta plain, southeastern Louisiana

Abstract

The dramatic loss of Louisiana's coastal wetlands and barrier shorelines is well recognized by government agencies, industries, universities, and the public. Between 1932 and 1990, the deltaic plain of the Mississippi River lost over 680,000 acres of land due to a complex suite of causes. Controversy and debate continues as to the causes of coastal land loss in Louisiana. Estimates of the human contribution of man to the land loss problem ranges between 10 percent and 90 percent (Britsch and Kemp, 1990; Penland et al., 1990, Penland et al., 1992; Turner, 1997). Several government agencies and industries have been targeted as the primary agent of coastal land loss including the U.S. Army Corps of Engineers (USACE) and the oil and gas industry. The role of natural processes and the multiple causality of the coastal land loss problem often have been overlooked (Boesch et al., 1994). In an effort to further our understanding and knowledge of the coastal land loss problem in Louisiana, the Gas Research Institute (GRI) sponsored a research project through the Argonne National Laboratory (ANL) entitled Natural and Human Causes of Coastal Land Loss in in cooperation with the U.S. Geological Survey (USGS). The study team consisted of scientists from GRI, ANL, Louisiana State University (LSU), University of New Orleans (UNO), USGS, USACE, and the Louisiana Universities Marine Consortium (LUMCON). This study focused on three major land loss research tasks: 1.) Geologic Processes, 2.) Vegetative processes, and 3.) Spatial Geographical Information System (GIS) Analysis. Through these research tasks, the objectives of this study are to quantify and rank the causes of coastal land loss within the Mississippi River delta plain in southeastern Louisiana. This study took advantage of continuing research by the USGS in framework geology and subsidence processes, and the USACE in GIS analysis, framework geology, and subsidence processes (Dunbar et al., 1990, Dunbar et al., 1992, Britsch and Dunbar, 1993; Williams et al., 1993). The geological processes task focused on the Holocene evolution of the Mississippi River delta plain in an effort to identify the regional geological controls on coastal land loss over the last 18,000 years. The vegetative processes task conducted field investigations into the role of salt-water intrusion and soil inundation in plant dieback. The GIS analysis task focused on quantifying the geomorphic forms and processes of coastal land loss using the USACE coastal land loss database. In this report, the results of the GIS geomorphic classification of coastal land loss are presented.