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The history of sediment flux to Atchafalaya Bay, Louisiana

By
John McManus
John McManus
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Published:
January 01, 2002

Abstract

The Atchafalaya became a free-flowing river system in the mid-nineteenth century. It progressively increased its diversion of waters from the Mississippi until, by the mid-twentieth century, it threatened to capture the total flow of the main river. The installation of control structures has, temporarily at least, prevented total diversion, limiting the flows to 30% of the Mississippi; water discharge and sediment transport into the Atchafalaya have led to deposition throughout the basin. A major system of lakes and bayous has become largely filled with deltaic sands and layered silts, so that the waters currently drain almost directly into the Atchafalaya Bay. The natural outlet and one artificially created outlet each carry waters from the system. As a result of major flooding in 1973, sediment was flushed from the Atchafalaya Basin and began the sub-aerial emergence of deltas, which had been slowly building below the bay water surface since the 1950s. The two deltas have provided, parallel growth one largely in natural form, and the other substantially modified by the dredging needed to maintain a navigable routeway to Morgan City and the interior of the basin. The sub-aerial deltas initially grew rapidly, a process apparently slowing, but the sediment transported to the depositional areas has not diminished, rather the area of deposition within the receptor basin is increasing, so that apparent growth inevitably slows. By 1994 the two deltas occupied an area of more than 153 km2 above the 0.6 m measuring datum, created in approximately 30 years. In each

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Contents

Geological Society, London, Special Publications

Sediment Flux to Basins: Causes, Controls and Consequences

S.J. Jones
S.J. Jones
University of Durham, UK
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L.E. Frostick
L.E. Frostick
University of Hull, UK
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Geological Society of London
Volume
191
ISBN electronic:
9781862394391
Publication date:
January 01, 2002

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