Sediment deposition in the lower Hudson River estuary

Abstract

This study uses geophysical and sedimentological data collected from the Lower Hudson River estuary to identify the depositional response of the estuary to high river discharge events. Erosional and depositional environments in the estuary are identified through the use of side-scan sonar, bottom penetrating sonar and surficial sediment sampling. Sediment cores are used to document deposit thicknesses and to obtain the spatial distribution of estuarine deposits. Results show a high degree of spatial and temporal variability in sedimentation within the estuary. Two primary deposits are identified underneath the turbidity maximum for the estuary. Approximately 300,000 metric tons of sediment were deposited within these two deposits during May and June of 1998. This short-term accumulation underneath the turbidity maximum of the estuary can account for 30 to 98 percent of the estimated, river-borne sediment load supplied to the estuary during the 1997-1998 water year. Both the tidally produced stratigraphy observed in sediment cores and the spatial distribution of identified deposits, support the theory that sedimentation underneath the turbidity maximum of the estuary is primarily the results of a convergence in bottom water flow, caused by the formation of a salinity front during ebb tide.