Geomorphic and Coastal Process Analysis for Ship Channel Planning at Ship Island, Mississippi

Abstract : Westward migration of Ship Island, Mississippi, has resulted in significant channel shoaling and increased maintenance dredging requirements of the Gulfport Harbor Ship Channel, requiring realignment of the channel to the west around the advancing island tip. The western island tip has migrated westward approximately 38 ft/year since 1848. The subaerial island area has decreased at the rate of 4.5 acres/year since 1948. As the Ship Island barrier system migrates westward, the gulf shoreline along the eastern end erodes, supplying sand to the advancing western tip. Alternative channel alignments were studied as potential solutions to the shoaling problems caused by the island migration. An alignment passing 1,900 ft west of the island tip would allow approximately 50 years before the island tip reaches the channel edge, based on the 38 ft/year migration rate. This alignment is favorable according to the following criteria: construction and maintenance costs as a function of dredging requirements; channel navigability; siltation potential; and complexity of design and construction. Keywords: Shallow water; Sediment transport; Channel(waterways); Water waves; Barrier island; Bathymetric analysis; Historic data; Shoaling; Wave refraction. (sdw)