River Discharge and Sediment Deposition in the Upper Pamlico Estuary

Abstract

A qualitative stability model was used to evaluate the Pamlico-Tar River system of North Carolina to determine possible impacts of upstream land use on sediment delivery to the estuary and the role of streamflow relative to other processes in defining the loci of sediment accumulation. Barring catastrophic or threshold-type changes in the watershed, rivers such as the Tar are dynamically stable with respect to sediment transport and storage. This suggests that fluvial sediment delivery to the estuary and fluvial influence on the geomorphology of the river/estuary transition zone will be relatively constant. Observed changes in upper-estuary sedimentation patterns should then be linked to changes in the coastal rather than the fluvial system. Because sediment yield/discharge relations are constant, and because tidal currents are negligible, wind-driven circulation determines the location of sediment accumulation within the boundary conditions defined by river flow. The interaction of wind-driven circulation and freshwater inflow creates a gradual, poorly defined river/estuary transition zone. The first step to understanding processes in the transition zone is tracking the movement of the river/estuary interface under various discharge and wind conditions.