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

The Albemarle-Pamlico Estuarine System (APES) in North Carolina (NC) is a region constantly undergoing physical changes associated with sea-level rise, storm events, and anthropogenic modification. The APES is a composite of inland river valleys within the coastal plain that have been flooded by sea-level rise over the Holocene (Kjerfve and Magill, 1989). It is anticipated that estuarine shoreline change and its controlling processes (e.g., storms, anthropogenic modification, and long-term sea-level change) also influence seabed sedimentation rates in the APES, specifically in estuaries around Roanoke Island, NC. Rates of estuarine shoreline change around Roanoke Island will be established to evaluate how local shoreline changes relate to sedimentation rate variability. Two primary hypotheses are proposed in this research: (1) high-intensity storm events are a primary driver for short-term shoreline change, particularly marsh erosion in the APES, and (2) estuarine shoreline change in response to storm events and sea-level rise has enhanced subtidal sedimentation over short- and long-term time-intervals. ArcGIS analyses of shoreline change and geochemical analyses of sediment grabs and cores are the dominant methodology applied in this research. Surficial grain size distributions of the sediment around Roanoke Island will be determined. Lead-210 and ¹³⁷Cs activities along with x-ray fluorescence (XRF) analyses will be performed in order to obtain sedimentation rates and elemental compositions of the samples. The dominant foraminiferal assemblage within selected cores will serve as additional potential tracers to establish a sediment source. Fifty eight surface grab samples were collected around Roanoke Island in an initial survey on December 19 and 20, 2013. These samples were collected using a Ponar bottom grab sampler and will analyzed for grain size. One push core was also collected and segmented into one centimeter intervals. More cores will be collected from dominantly muddy locations for the further geochemical analyses. This study will produce quantifiable data pertaining to shoreline change and how adjacent estuarine sediment dynamics are affected in this modified estuarine system.