A COUPLED GEOLOGIC AND HYDRODYNAMIC MODELING APPROACH TO HINDCAST AND FORECAST THE RESPONSE OF A COASTAL SYSTEM TO SEA-LEVEL RISE AND GEOMORPHIC CHANGE

We are using observations and analyses of coastal stratigraphy and geomorphology, paleobathymetric models, and a hydrodynamic model (ADCIRC) to understand past and future responses of a critically threatened coastal system to changes in tidal amplitude, currents, and sediment transport which correspond to geomorphic/paleobathymetric changes related to storm impacts and sea-level rise. The modeling approach is based upon geologic observations of late Pleistocene and Holocene facies within and surrounding the Albemarle-Pamlico Estuarine System (APES) and the associated Outer Banks (OBX) of North Carolina, derived from seismic data, cores, and microfossil assemblages, temporally constrained by radiocarbon and optically-stimulated luminescence ages. Based upon existing data, we understand that major coastal reorganization occurred in the past, and will occur in the future, and is accompanied by rapid transitions in the tidal regime and sediment transport processes in response to sea-level rise and degree of barrier island continuity. To understand the process response, we are developing bathymetric/paleoenvironmental models of the APES system at specific time slices (past and future), and modeling the tidal effects (amplitude, currents, bed shear stress) with ADCIRC, using various representations of barrier island morphology, which are constrained by our geologic observations. Model outputs of currents and bed shear stress are being compared to sedimentological and paleoenvironmental data to determine the degree of correspondence of the model with observations, robustness of the method, and to identify discrepancies. These data will facilitate an understanding of the past coastal system process response, and the potential for future changes.