ABSTRACT

The dramatic loss of Louisiana's coastal wetlands and barrier islands is well recognized by government agencies, industry, universities, and the public. Between 1932 and 1990, the Mississippi River delta lost over 690,000 acres of land. Controversy and debate continue as to the causes of deltaic land loss. Estimates as to the contribution of man range between 10% and 90%. The U.S. Army Corps of Engineers and the oil and gas industry have been targeted as the primary agents of land loss. The causes are complex and varied; foremost, man has altered the hydrology of the Mississippi River flood and diversion control, disrupting the regional dynamic equilibrium of this delta's wetland. A geologic coastal land loss classification is presented in this paper that describes the form, or geomorphology, of localized areas of loss and the causes or processes of this loss.

The geomorphology of coastal land loss can be classed as either shoreline or interior. The shoreline class can be further subdivided into gulf, bay, lake, and channel. The interior class can be further subdivided into pond and channel. GIS analysis of the digital coastal land loss database documents the shoreline class, accounting for 207,927acres of loss (30.0%) and the interior class accounting for 483,004 acres of loss (69.91%).

The processes of coastal land loss can be classed as erosion (3 subclasses), submergence (9 subclasses), or direct removal (8 subclasses). GIS analysis of the digital coastal land loss database documents that the erosion class accounts for 213,280 acres of loss (30.87%), submergence class accounts for 375,613 acres of loss (54.36%), and the direct removal class accounts for 103,038 acres (14.77%) of loss. The top three process classes are oil and gas at 36.06%, followed by natural waves at 26.21% and altered hydrology at 21.52%) for a total of 83.79%. The remaining 15 subclasses account for only 16.21%. These results document the complexity of the coastal land loss problem and the importance of man in driving this environmental disaster in America's delta, the Mississippi.