PREDICTING EROSIONAL EFFECTS OF THE TIDAL INFLUENCE ON SAPELO ISLAND, GA FROM ARCHIVAL IMAGERY AND GPS TRACKING

Sapelo Island, GA is one of many drumstick barrier islands that make up the coast of Georgia as it meets the Atlantic Ocean. Here, a large tidal influence has created a diverse tidal salt marsh ecosystem and an extensive system of tidal channels that exist solely to distribute the inundation of the area during high tide. These channels exhibit erosional cut banks and depositional point bars associated with meandering fluvial streams. Many cut banks are aligned to actively erode the barrier beach in the direction of the open ocean, as is the case with a cut bank in a local tidal channel called Blackbeard Creek. Through the analysis of archival imagery and UTM GPS data from Google Earth using the Pythagorean Theorem and Microsoft Excel, this cut bank was determined to be actively eroding the beach deposits between 1988 and 2012. During this period, however, the beach also experienced accretion of sediment with the difference between these values representing an average net erosion eastward. Collected data regarding beach thickness and variables such as mean sea level rise and historical storm events, when mathematically modeled, suggests that the cut bank may theoretically breech the open ocean at some point during this century, thus affecting the volume, flow velocity, and chemical characteristics of the sea water influx during flood tide events. Given the environment’s sensitivity to changes in variables such as salinity and soil nitrification, this event could significantly affect the diverse and important salt marsh that the barrier both created and protects.