Submersed aquatic vegetation is an important modulator of sediment delivery from the Susquehanna River through the Susquehanna Flats into the Chesapeake Bay. However, the dynamic interactions between vegetation and the physical drivers of sediment transport through the region are not well understood. This study used a new vegetation component in a coupled flow-wave-sediment transport modeling system (COAWST) to simulate summer through fall 2011, when the region experienced a sequence of events including Hurricane Irene and Tropical Storm Lee. Fine sediment was exported under normal flows and high-wind forcing but accumulated under high flows, with accumulation doubling in the presence of vegetation. The relative effects of vegetation under normal flows and high-wind forcing depended on previous sediment dynamics. The presence of vegetation facilitated deposition of fine sediments within the patch under normal flows and subsequent resuspension during a wind-driven event. However, during significant discharge events, the system was completely dominated by riverine dynamics with vegetation enhancing net deposition as well as channeling the flow. While further refinement of the bed model may be needed to capture some nuances, the COAWST modeling system provides new insights into detailed sediment dynamics in complex vegetated deltaic systems.
