Calculating shoreline erosion potential using nearshore stratigraphy and sediment volume: Outer Banks, North Carolina

Despite the acknowledged influence of coastal geological framework on the behavior of beaches and barrier islands and a wealth of geological and bathymetric observations from the inner shelf, quantitatively connecting those observations to shoreline behavior has been difficult. Nearshore geologic and morphologic variability described by recent research is not well represented by conventional geologic parameters, such as mean grain size and shoreface slope, used in most shoreline change models. We propose that total nearshore sediment volume, as calculated to a continuous seismic reflection surface, provides a flexible and robust metric for use in the prediction of shoreline change. This method of determining the volume of sediment in the nearshore accounts for three‐dimensional sandbar morphologies and heterogeneous seafloor sediments. The decadal‐scale shoreline change rate for northeastern North Carolina is significantly correlated to the volume of sediment in the nearshore when a geologically defined base is used in volume determinations, suggesting that the shallow stratigraphic framework of transgressive coasts is an important influence on decadal shoreline behavior. Nearshore sediment volume was overestimated when an arbitrary depth‐constant baseline was used and was not correlated to decadal shoreline change. This implies that a volume metric which accounts for both framework geology and variable seafloor morphology better represents the geologic character of the shoreface and may help to improve existing models of shoreline change. An empirical model of regional shoreline erosion potential demonstrates the importance of incorporating nearshore sediment volume, shallow framework geology, and surface morphology when predicting seasonal to decadal shoreline evolution.