Shoreline Response to Changes within a Small-Scale, Mesotidal Inlet System: Goulds Inlet, Georgia

Goulds Inlet separates Sea and St. Simons Islands and is comparatively small compared to most inlets along coastal Georgia. In the past, shorelines located adjacent to the inlet have experienced erosion and accretion at varying magnitudes. Although the inlet's present location appears to be relatively stable, historically the inlet has migrated south, thus extending the Sea Island spit. As a result, shoreline accretion/erosion processes are driven by complex linkages between the movements of the ebb channel, asymmetry of the ebb-tidal delta, and migration of swash bars. Georectified aerial photos of the study area spanning roughly sixty years (1942-2000) were used within ArcGIS to delineate the high-water line (HWL) shoreline, ebb delta shoals, and the middle of the inlet channel and stored as shapefiles. Measurements of spatial and temporal changes of these features were performed within ArcGIS using ArcToolbox and in-house scripts. Preliminary results of the shoreline change analyses suggest net long-term accretion along the adjacent shorelines. However, a small segment on the St. Simon's inlet shoulder was identified that has net long-term erosion (~ -1.5 m/yr). This portion of the shoreline appears to be less influenced by the ebb delta morphology and more so with the position ebb channel's thalweg and periodic advance and retreat of the Sea Island spit. A few hundred meters south of this shoreline segment, net accretion is occurring along a “bulge” in the shoreline associated with inlet swash bar welding. Cursory inpection of the aerial photos suggests the shoreline position along this region also tends to fluctuate in response to the movement/orientation of the ebb channel and changes in ebb delta symmetry (~ +1 to 7 m/yr). More aerial photos and historical maps are being added to the GIS database to better ascertain long and short-term trends.