Attenuation of Geomorphic Capital Along an Ebb-Dominant Mixed-Energy Barrier Island

Abstract Debidue Beach and North Inlet are a coupled mixed-energy inlet-barrier system along the South Atlantic Bight in South Carolina, USA. Long-term chronic erosion along much of Debidue throughout the 20 th century is the result of a shoreline adjustment triggered by an avulsion in the main channel of North Inlet occurring between 1926 and 1934. We use a historical database of shoreline positions compiled by the United States Geological Survey (USGS) and the Analysis of Moving Boundaries Using R (AMBUR) package to quantify changes in the Debidue Beach shoreline over nearly 150 years from 1872 to 2011. This analysis documents relatively large-scale shoreline changes (and equivalent volumetric changes above local depth of closure ‘DOC’) following the shift in channel position, and a logarithmic decrease in erosion rates over the following decades. Mixed-energy ebb-dominant inlets have considerable effect on adjacent beaches due to their ability to retain and shed large quantities of sand relatively quickly. This study demonstrates that even systems exhibiting long-term stability – like North Inlet – are indeed migrational landforms and should be considered as such when formulating shoreline management plans along adjacent beaches.