Examination of Estuarine Sediment Dynamics : Insights from the Large, Shallow, Albemarle-Pamlico Estuarine System, NC, U.S.A.

Abstract

This dissertation investigated the dynamics of estuarine shorelines in the Albemarle-Pamlico Estuarine System (APES). Shoreline change is influenced by human activities (e.g., shoreline modification), and natural processes (e.g., waves, storms, and sea-level rise) on variable temporal and spatial scales in the coastal zone. This research examined the spatio-temporal dynamics of shoreline change, the drivers of that change, and the role of shoreline erosion in the sediment dynamics of the larger estuarine system. Historical rates of change were found to be comparable to previous studies at -0.5 ± 0.07 m yr⁻¹. Decadal and sub-annual rates of change were highly variable over the study, both spatially and temporally. However, linear regression models indicate that the large changes in shoreline position observed in high-frequency (bi-monthly) surveys are captured within the long-term (historical) average rate of shoreline change. Simulations from a coupled hydrodynamic and wave model indicate that waves and storms (hurricanes) are important drivers of shoreline change. Wave energy along different shorelines was found to be dependent on shorezone characteristics such as shoreline orientation, wind direction and fetch, and nearshore bathymetry. The role of shoreline erosion in the sediment dynamics of the larger estuarine system was also investigated for a region of the APES, the Tar-Pamlico estuary. Shoreline erosion and shoreline modification were examined within the estuary in order to explore the significance of erosion as a source of fine sediment to the estuary. Sediment storage was also evaluated for the Tar-Pamlico estuary using rates of sediment accumulation determined from the radionuclide tracers of ²¹⁰Pb and ¹³⁷Cs. A fine sediment budget was constructed for the Tar-Pamlico estuary. The budget indicates that eroding wetland shorelines represent a significant (43% of total fine sediment input) source of material to the estuary. Also, the majority of fine sediment is retained within zones of accumulation within the estuary, with only about 7% potentially exported to the adjacent Pamlico Sound. Overall, this research highlights the dynamic process of estuarine shoreline change, and the role of that change in the functioning of the larger estuarine system. Coastal managers need to incorporate an understanding and accommodation of these processes into future management plans for North Carolina's estuarine shorelines.