MODERN BACK-BARRIER SEDIMENT AND HYDRODYNAMIC PROCESSES

Barrier islands are found around the world, and their geomorphic evolution is related to ocean and estuarine processes. More research is needed on back-barrier areas being affected by an array of processes. Rodanthe, North Carolina is a town on the Outer Banks that is bounded by the Atlantic Ocean and Pamlico Sound. The Rodanthe back-barrier coast consists of undulating shoreline, adjacent to a broad (~4 km) shallow seabed (<2 m) widely covered with submerged aquatic vegetation (SAV). Shoreline and volumetric change rates, bathymetry, surface sediment grain properties, and hydrodynamic conditions were measured to evaluate sediment processes along with SAV patterns and change over time. Shoreline change rates (SCR) were evaluated using aerial photographs from five time steps (1949 to 2015), and the long-term SCR as -0.41 m/yr but there was much variability. Singlebeam bathymetric surveys revealed a broad, shallow expanse across the SAV region with two sand bars at a 4 km depth break near the western (sound-side) SAV boundary. Surface sediment grab samples display modest variation in grain-size distribution across the region with a dominance of fine sands. Data are being used to evaluate spatial variability and change over time.