Littoral Sediment Budget for the Mississippi Sound Barrier Islands

Abstract : Shoreline and beach evolution for the barrier islands fronting Mississippi Sound are driven by longshore transport processes associated with storm and normal wave and current conditions. Although beach erosion and washover deposition are processes that have influenced island changes, the dominant mechanism by which sand is redistributed along the barrier islands and in the passes is by longshore currents generated by wave approach from the southeast. Historical shoreline and bathymetric survey data were compiled for the barrier islands and passes fronting Mississippi Sound to identify net littoral sediment transport pathways, quantify the magnitude of net sand transport, and develop an operational sediment budget spanning a 90-year period. Net littoral sand transport along the islands and passes is primarily unidirectional (east-to-west). Beach erosion along the east side of each island and sand spit deposition to the west result in an average sand flux of about 300,000 to 400,000 cy/yr throughout the barrier island system. Dog Keys Pass, located updrift of East Ship Island, is the only inlet acting as a net sediment sink and is the widest pass in the system (about 6 miles). As such, a deficit of sand exists along East Ship Island. Littoral sand transport decreases rapidly along West Ship Island, where exchange of sand between islands terminates because of wave sheltering from shoals and islands of the old St. Bernard delta complex, Louisiana. These data are being used to assist with design of a large island restoration project along Ship Island, Mississippi.