AN INTEGRATED GIS-BASED APPROACH TO QUANTIFYING THE RATES OF SHORELINE CHANGE IN THE GEORGIA BIGHT: A PROGRESS REPORT

The South Carolina/Georgia Coastal Erosion Study is a USGS cooperative program administered through the South Carolina Sea Grant Consortium. The goals of the Georgia portion of the program are twofold: 1) to determine the historical rates of shoreline change in Georgia and southernmost South Carolina and 2) to synthesize existing knowledge to identify gaps in our understanding of coastal processes in the Georgia Bight as a guide for further research.

Historical shoreline change was determined using aerial photographs from the late 1950s, 1979, and 2000. USGS Digital Orthophoto Quarter-quads (DOQQs) from 1993 were used both for shoreline position and for selecting ground control points for georeferencing the photographs. Ground control points were carefully identified from the base-layer DOQQs and assigned to each photograph. Each photograph was then registered into ArcView. The wet/dry line was then digitized into an ARCView polyline shapefile. Shoreline position for periods prior to aerial photography were derived from T-sheets which were scanned, digitized, georeferenced and imported into ARCView. Shoreline change rates varied from +8 m/y to -2 m/y. Typically the northern ends of Georgia barrier islands are eroding and the southern ends are accreting.

The second component of this program involves generation of a digital State of Knowledge report for the coast and inner shelf. This ongoing effort will permit identification of gaps in the state of current geodata. We are reviewing published and gray literature citations on historical coastal change, extents and impacts of coastal engineering, and the role of the post-Mesozoic stratigraphic framework in coastal evolution.