Abstract
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
