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ABSTRACT: Coastal Geomorphology and Landscape Changes in the Pontchartrain Basin


Lakes Maurepas and Pontchartrain have served as a historical natural, economic, and recreational resource to New Orleans and the communities surrounding this basin. Natural and human processes are causing an environmental decline of this basin. In order to better manage this natural resource, the U.S. Geological Survey in cooperation with Louisiana State University, are conducting a 5-year study of this valuable ecosystem. This paper presents new information on coastal geomorphology and landscape changes in the basin.

Four basic coastal types have been mapped. These include swamp (34.2% or 46.64 miles), marsh (28.5% or 38.74 miles), beach (4.2% or 5.67 miles), and armored shorelines (33.1% or 45.10 miles). In terms of coastal erosion, 45.10 miles of shoreline are stabilized by armored structures and the remaining 53.55 miles of shoreline are experiencing erosion. The highest erosion rates occur between Frenier Beach and the Bonnet Carre Spillway where erosion rates exceed 14 feet per year. Overall, the lowest rates of erosion are found in Lake Maurepas, where rates are less that 7 feet per year. Erosion rates in Lake Pontchartrain average 7 to 14 feet per year where the shoreline is not armored.

The major landscape changes occurring over the last 100 years include freshwater marshes changing to higher salinity marshes, cypress swamps changing to freshwater marshes, and the loss of wetlands due to urbanization.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana