Bathymetric Comparisons Adjacent to the Louisiana Barrier Islands: Processes of Large-scale Change
Keywords:Erosion, sea-floor change, sediment budget, sea-level rise, ebb-tidal delta, Louisiana, Mississippi Delta
This paper summarizes the results of a comparative bathymetric study encompassing 150 km of the Louisiana barrier island coast. Bathymetric data surrounding the islands and extending to 12 m water depth were processed from three survey periods: the 1880s, the 1930s, and the 1980s. Digital comparisons between surveys show large-scale, coherent patterns of sea-floor erosion and accretion related to the rapid erosion and disintegration of the islands. Analysis of the sea-floor data reveals two primary processes driving this change: massive longshore transport, in the littoral zone and at shoreface depths; and increased sediment storage in ebb-tidal deltas. Relative sea-level rise, although extraordinarily high in the study area, is shown to be an indirect factor in causing the area's rapid shoreline retreat rates.