A Coupled Wave-Current-Sediment model for Skagit Bay

Along with tidal currents, waves provide a dominant forcing mechanism for sediment transport on many tidal flats. In semi-enclosed regions such as Skagit Bay, Washington, the wave action is due mainly to local wind forcing that occurs over seasonal and event scales. Due to the limited fetch, variations in along-flat wave characteristics can drive gradients in the wave-induced bottom stress and resulting sediment transport. In this work, we use an unstructured grid, coupled wave-current-sediment model to study the influence of wave-induced near bottom stresses in the presence of tidal currents on the sediment transport within the Skagit River delta and Skagit Bay. The coupled model consists of three primary components: the Finite Volume Coastal Ocean Model (FVCOM) for hydrodynamics, the unstructured grid model SWAN to compute the phase-averaged wave field, and the Community Sediment Transport Modeling System. Model sensitivities to the choice of coupling and bottom boundary layer formulations are examined. Results from process oriented simulations will be presented. The process studies use a realistic domain with controlled forcing conditions to quantify the influence of wave-induced bed stresses on the sediment dynamics in Skagit Bay.