--> ABSTRACT: Winter Storm Impacts on Chenier Plain Coast of Southwestern Louisiana, by Harry H. Roberts, Oscar K. Huh, S. A. Hsu, Lawrence J. Rouse, Jr., and Douglas A. Rickman; #91029 (2010)

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Winter Storm Impacts on Chenier Plain Coast of Southwestern Louisiana

Harry H. Roberts, Oscar K. Huh, S. A. Hsu, Lawrence J. Rouse, Jr., Douglas A. Rickman

Stormy conditions associated with periodic winter cold front passages are closely related to transport of suspended sediment to the continental shelf, coastal erosion, and coastal progradation along shoreline sectors where abundant fine-grained sediments are stored on the inner shelf. Cold front passages occur between October and April on 3 to 5-day cycles. Their typical northwest to southeast direction of approach, large spatial scales, and numerous yearly occurrences (20-30 cycles/year) drive physical processes that cause significant coastal change.

Acquisition of both remotely sensed multispectral and high-quality photographic data, collected from altitudes of 1,500, 9,000, and 21,000 m before and after cold front passages, forms a database for evaluating coastal change and suspended sediment transport pathways. Satellite imagery provide a longer term perspective on coastal change. Remotely sensed data sets are augmented with ground truth measurements of coastal configuration, sedimentological framework, and water quality.

Physical processes active in the prefrontal rapid cold front passage are considerably different from post-frontal phases. Along the chenier plain coast, prefrontal periods are characterized by prolonged periods (days) of high wave action from the southerly quadrants, water level setup along the coast, and strong along-shore and onshore sediment transport. At these times, mud from the Atchafalaya River, stored on the nearshore shelf, is transported onshore and along shore to add an increment of progradation to the chenier coast. Post-frontal conditions bring dry cold winds from the northerly quadrants, causing water-level lowering along the coast, a significant reduction in nearshore wave energy, and drying of the newly deposited mudflats fronting the chenier plain. Rapid drying causes an important increase in sediment strength, mud-crack formation, and effective armoring of the mud flats by dried mud clasts that resist erosion in subsequent cycles.

AAPG Search and Discovery Article #91029©1989 AAPG GCAGS and GC Section of SEPM Meeting, October 25-27, 1989, Corpus Christi, Texas.