Assessment of Erosive Conditions at Cumberland Island National Seashore in Southeast Georgia

Abstract

Over the past several decades, the shoreline on the intracoastal waterway at Cumberland Island National Seashore has experienced what appears to be chronic erosion. This has become increasingly concerning because, in recent years, this erosion has resulted in revelation of a formerly unknown ancient burial ground with human remains. This study was conducted to assess whether regular semi-diurnal tidal flow causes regular sediment movement at this site and to assess the effects of worst-case storm conditions. A computational mesh of the southeastern United States/Caribbean was adapted from a previous study, refined near Cumberland Island, and used to compute water elevations and velocities in the area during several typical tidal cycles using ADCIRC. Results showed good agreement between measured and modeled results, and as such, modeled velocities were used to approximate bed shear stresses. Results appeared to indicate that sediment movement is initiated during regular tidal cycles, and this may be one of the reasons that the site appears to be chronically eroding. And, during certain worst-case storm events, these erosive conditions may become severely exacerbated both in duration and amplitude.