AN INTEGRATED GIS-BASED APPROACH TO QUANTIFYING THE RATES OF SHORELINE CHANGE IN THE GEORGIA BIGHT: FINAL RESULTS

The Georgia portion of a USGS-funded SC/GA Coastal Erosion Study has been focused on lab-based analyses of shoreline change and data gaps within the coastal scientific literature. Shoreline change information was determined using GIS analysis of historic and modern shoreline positions derived from NOAA tide sheets and aerial photography. These data have been used to produce a series of maps showing areas of coastal erosion, accretion and critically eroding coast. These maps illustrate the response of the barrier islands to eustatic sea level rise and the integrated results of southward longshore transport of sediment within the GA Bight.

Long-term (100-y timescale) shoreline change analysis of the GA barrier islands suggests erosion at rates of -2 to -3 m/y along the northern sections and variability in rates, ranging from -3 to +5 m/y, in the southern sections of the islands. In contrast, the central sections of most of the barriers are accreting at +1 to +2 m/y. These results suggest a relationship between tidal inlet morphodynamics and shoreline change along adjacent beaches. However, further detailed analyses are needed to delineate the extent of erosional influence adjacent to tidal inlets and to identify the role of local geologic framework on island-wide shoreline change. Currently, a new digital shoreline analysis technique is being developed and tested to aid in the statistical demarcation of hazard zones.

A State-of-Knowledge Report and bibliography of 1300 citations focused on coastal geology and engineering has also been produced. Priority coastal data and research needs identified in the report include: high-resolution imagery of the shallow subsurface; function and role of ebb-tidal deltas; high-frequency resolution of Quaternary sea-level history; sediment transport patterns on the nearshore shelf and validation assessment of numerical shoreline behavior models.