Fine grain sediment transport and deposition in the Atchafalaya and Chenier plain sedimentary system

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Conference Proceeding

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The most extensive land loss and land accretion processes in the U.S. are occuring in the Mississippi River Delta Plain. Some 40 square miles of valuable marshlands are lost annually. However, discharge of one third of the Mississippi River waters through the Atchalfalaya Basin is now rapidly building land, deltas in Atchafalalaya Bay and prograding mudbanks along the Chenier Plain. Studies of these coastal processes is underway combining field work with the data from remote sensing systems. Remote sensing systems being used include the NOAA Satellite AVHRR, the Multispectral Atmospheric Mapping System, the Calibrated Airborne Multispectral Scanner, SPOT satellite imagery and color aerial photography. Storms, both winter cold front passages and the occasional hurricane actually build up the muddy coasts by heaving fluid mud onto the shoreface where it becomes stranded. The deposit consists of a centimeter or so of sand/shell overlain by a 6-8 cm layer of mud. The mud begins dewatering by evaporation and by percolation through the sand/shell lamina. It becomes sun dried, dessicates, hardens, cracks into mudcrack cobbles which resist wave erosion. The transition from fine to very coarse grained sediment stabilizes newly accreted sediment against the coast. This process has caused recent progradation (1987-1990) of up to 200 m per year along the Chenier Plain coast west of Morgan City, La. Newly formed land is quickly colonized by marsh grasses. Cold front passages and hurricanes have essentially the same effect, with hurricanes just creating larger mud layers.

Publication Source (Journal or Book title)

Coastal Sediments '91

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