Paper No. 4
Presentation Time: 2:30 PM
HISTORICAL CHANGES OF GOULDS INLET, GEORGIA, FROM GEOSPATIAL ANALYSIS OF AERIAL PHOTOGRAPHS
Goulds Inlet is a relatively small Georgia inlet running between St. Simons and Sea Islands. Typically, inlet dynamics cause adjacent shorelines to experience varying degrees of erosion and accretion as hydrographic conditions vary seasonally or at longer temporal scales. Goulds Inlet, though seemingly stable, has historically migrated south, hugging the St. Simons shoreline, allowing the Sea Island spit to follow suit, building towards the south. The relative persistence of the inlet channel against St. Simons Island creates shoreline accretion/erosion processes driven by complex linkages between the movements of the ebb channel, asymmetry of the ebb-tidal delta, and migration of the swash bars. Georectified aerial photos of the study area spanning roughly sixty years (1942-2003) 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. 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 (shoreline movement averaging about -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. Inspection 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.