MODERN SUBTIDAL SEDIMENTATION AND ESTUARINE SHORELINE CHANGE AROUND ROANOKE ISLAND, NORTH CAROLINA

Croatan and Roanoke Sounds in North Carolina (NC) are regions constantly undergoing geomorphic changes associated with sea-level rise, storm events, and anthropogenic modification. These estuaries are part of the larger Albemarle-Pamlico Estuarine System (APES), a composite of drowned coastal plain river valleys and large bar-built shallow sounds behind the Outer Banks barrier islands. We hypothesize that changes in shoreline morphology driven by erosion and accretion associated with oceanographic/atmospheric drivers (e.g., wave action, fetch) influence modern sedimentological patterns and sedimentation rates in the APES. While previous studies have examined the Quaternary evolution of this region, this research focuses on the dynamics and controlling parameters of modern sedimentary processes around Roanoke Island, NC. Fifty eight surficial sediment samples were collected nearshore around Roanoke Island and characterized based on grain size and organic content. In addition to this data, side-scan sonar and chirp seismic data have been collected and are currently being examined to help interpret nearshore sediment dynamics in a region undergoing high rates of shoreline erosion. Historical maps and aerial imagery have been collected for shoreline change analysis around the island. We intend to evaluate whether shoreline change variations over the past 150 years have influenced seabed sedimentation rates in the surrounding estuaries. Sedimentological (e.g., grain size, LOI, etc.) and radiochemical (e.g., ²¹⁰Pb and ¹³⁷Cs) analyses are currently being performed on several short (~50 cm) cores collected throughout the study area to provide data on inter- and intra-site variability of sediment characteristics and rate of decadal-scale accumulation. It is our intent to use the geophysical data in conjunction with the modern sedimentological data to relate decadal shoreline morphological change to adjacent estuarine sediment dynamics.