QUANTITATIVE SHORELINE CHANGE ANALYSIS OF THE GEORGIA COAST FROM AERIAL PHOTOGRAPHY

Historical rates of shoreline change for Georgia''s barrier coastline are lacking in quantity and quality. The mostly unpublished research is limited in quality owing to technology limits at the time of study, but does provide a general understanding of erosion around each island as well as long-term patterns. A current project underway is part of the USGS South Carolina/Georgia Coastal Erosion Study administered through the South Carolina Sea Grant Consortium. The study is being conducted using the geographic information system (GIS) ArcInfo 8, along with ArcView Spatial Analyst, and Digital Shoreline Mapping System (DSMS). Shoreline change is being quantified from data that was extracted from rectified aerial photographs, NOS T-sheets, and USGS digital orthophotoquads using the wet/dry line as datum. Erosion rates are calculated using onscreen measurement in ArcView, DSMS, and ArcInfo's Grid module. Shoreline change rates vary from +8 m/y to -2 m/y. Typically the northern ends of Georgia barrier islands are eroding and the southern ends are accreting. Once completed, the study will aid in providing a baseline for setbacks, establishing long and short-term erosion rates, constructing risk assessments, and undertaking coastal planning with a higher level of accuracy. In addition to creating a scientific basis for shoreline monitoring and management, shoreline change calculations will also provide useful data on the impacts of engineering structures on erosion, which is needed to fully understand the consequences that may surround emplacement of a specific type of structure. This information can be used to provide effective recommendations on management issues with minimal impacts to the environment. Therefore, it may be possible to devise shoreline management strategies that anticipate and plan for shoreline erosion due to sea-level rise and coastal storms.