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Historical shoreline and bathymetric survey data were compiled for the barrier islands and passes fronting Mississippi Sound to develop a regional 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 430,000 cy/yr throughout the barrier island system. Dog Keys Pass, located updrift of East Ship Island, is the only inlet that is a net sediment sink. It also is the widest pass in the system and has two active channels and ebb shoals. As such, a deficit of sand exists along East Ship Island. Littoral sand transport decreases rapidly on 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.Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it Historical shoreline and bathymetric survey data were compiled for the barrier islands and passes fronting Mississippi Sound to develop a regional 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 430,000 cy/yr throughout the barrier island system. Dog Keys Pass, located updrift of East Ship Island, is the only inlet that is a net sediment sink. It also is the widest pass in the system and has two active channels and ebb shoals. As such, a deficit of sand exists along East Ship Island. Littoral sand transport decreases rapidly on 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.

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A computer-based shoreline mapping methodology, within the framework of a geographic information system, was used to compile and analyze changes in historical shoreline position and island area between 1847/49 and 1986 for the Mississippi Sound barrier island system. The data base consisted of three to four cartographic shorelines and one to two air photo interpreted shorelines. The dominant direction of movement for Dauphin, Petit Bois, Horn, and Ship islands is to the west, whereas cross-shore change in shoreline position is the primary mechanism by which the beaches on Cat Island respond to incident processes. Average shoreline change for the study area was about -1.7 m/yr; however, Horn Island illustrated no net shoreline change for the period of record and the western halves of Petit Bois and Ship islands were net progradational. Although spatial variability in shoreline movement was common, associated land loss was relatively consistent, ranging from -1.6 to -2.5 ha/yr. The magnitude of lateral island migration is generally an order of magnitude greater than cross-shore movements. East of Dog Keys Pass, the islands are moving to the west by updrift erosion and downdrift accretion at rates exceeding 30 m/yr. The eastern end of Petit Bois Island illustrates the greatest lateral movement, averaging 89.9 m/yr between 1848 and 1986. Long-term changes recorded for the ends of Ship Island are significantly smaller, mainly due to dredging at the Biloxi navigation channel and distance from sand source, limiting the quantity of sand available for natural bypassing to the west. Short-term lateral migration trends illustrate a similar response at Horn Island Pass.