Storm layer deposition on a coastal louisiana lake bed

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Li, H.; Lin, L., and Burks-Copes, K.A., 2013. Modeling of coastal inundation, storm surge, and relative sea-level rise at Naval Station Norfolk, Norfolk, Virginia, U.S.A. Tropical cyclone impacts on wetland, terrestrial, and shelf systems have been previously studied and reasonably delineated, but little is known about the response of coastal lakes to storm events. For the first time tropical cyclone impacts on a shallow coastal lake in the Louisiana coastal plain have been studied using direct lines of evidence. Using side-scan sonar, CHIRP subbottom, and echo sounder bathymetric profiles, the lake bottom and shallow subsurface of Sister Lake was imaged pre- and post-Hurricanes Katrina and Rita to provide a geologic framework for assessing storm effects. Box cores were collected to provide site-specific "ground truth" data to further evaluate the accretion or erosion of sediment over the short storm period between synoptic geophysical surveys. X-ray radiographs of box cores showed clear increments of recent event sedimentation (1-10 cm in thickness), corroborated with radionuclide dating as being products of the storm period. High percentages of approximately 40% fine sand in the storm layer and its thickness relative to an average long-term sedimentation rate of 2.0 mm/y suggest that transport of storm-related sediments from the inner shelf is a large factor in Sister Lake sedimentation. This study provides a framework and fundamental understanding of lake bottom characteristics and impacts of storm-related physical processes on erosion, sediment resuspension, and deposition. For a general case of subsidence in the Louisiana coastal plain of 6-8 mm/y and future sea-level rise rate of at least 3 mm/y, the sediment deficit for Sister Lake is 7-9 mm/y, which suggests that Sister Lake will deepen and widen with time. © Coastal Education & Research Foundation 2013.

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Journal of Coastal Research

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