Hurricane Overwash and Decadal-Scale Evolution of a Narrowing Barrier Island, Ocracoke Island, NC

Barrier islands are found around the world and are important environmentally and economically. With accelerated sea level rise and relentless storms, their evolution is complex but important to understand, especially from a coastal planning and managing perspective. In this study, shoreline change estimates from aerial photography (1949, 1974, 2006), sedimentological and stratigraphic investigation, and analysis of geomorphic character were used to evaluate the hurricane response and decadal evolution of Ocracoke Island, NC. Between 1949 and 2006, the majority (> 65% of transects) of the entire island eroded at an average rate of - 0.54 m/year. Cross-island width decreased by as much as 40% (180 m) over the period. Hurricane Isabel (2003) represented up to 23% of the long-term net change in some regions of the island. The rate of narrowing of Ocracoke Island appears to have increased in the last half century and is due to a combination of natural and anthropogenic factors. Isabel overwashed a total of 9% of the island based on aerial photographic analysis with an average deposit thickness of 0.24 m based on trench investigation. Assessment with the Storm Impact Scale showed a direct relationship between overwash and the pre-existing dune conditions, which had been affected by long-term erosion. Sedimentological signatures interpreted from cores show up to four distinct stacked overwash deposits, potentially dating back as far as 1944. This multi-pronged analysis shows the complexity of barrier island evolution and highlights the necessity to examine and model a system response in four dimensions (i.e., spatially and with time).