Simulation and Observation of the Bottom Stress Distribution in a Large Estuary

The stability and transport of sediments in an estuary are largely determined by the bottom shear stress and the circulation. To select appropriate sites for the disposal of material dredged from harbors and inlets in the eastern end of Long Island Sound we developed an implementation of FVCOM and tested it with the results of an extensive observational study that augmented existing observations with particular emphasis on the eastern end of Long Island Sound and Block Island Sound. Three two-month campaigns were executed to describe the spring, summer and winter conditions. Bottom stress was measured at seven locations. The model showed excellent agreement with the measurements of sea level, currents, and salinity. Bottom stress evaluation showed that model was capable of discriminating areas of high maximum stress from areas of low bottom stress. The evaluation suggest that a spatially variable bottom stress coefficient may improve the model performance. The model was used to identify area where the maximum bottom stress was low, less than 0.75 Pa, which is thought to be characterisitc of the critical shear stress for dredged material in the region. Some of these areas may be candidates for future disposal of dredged material