Affect of Seabed Density and Sediment Pelletization on Erosion/Deposition Processes at Clay Bank, York River, Chesapeake Bay, Virginia

We have examined the relationships among seabed density, sediment pelletization, erosion/deposition patterns and their changes through time and space at the partially mixed, microtidal Clay Bank, York River (CB-YR), Chesapeake Bay subestuary. Previous studies describe the CB-YR site as a dynamic area with seasonal and spatial variations in sediment transport. Acoustic profiles and radiochemical analysis show low rates of deposition during winter and early spring seasons in cohesive sediments across and along the CB-YR site. Low sediment pelletization was also found during winter/early spring seasons due to the limited biological activity, which may explain the low deposition rates. High bulk density measurements during winter/early spring signify the removal of the pelletized sediments from the seabed, inducing high erosion rates. Volumetric calculations of the upper seabed layer indicate high variability in sediment distribution at the Clay Bank-York River site. We attribute the bulk of these changes to both biological and physical factors, which vary markedly between winter/early spring and summer/fall seasons.