Roles of Wind-Driven Currents and Surface Waves in Sediment Resuspension and Transport During a Tropical Storm

Satellite remote sensing shows two hot spots of high suspended sediment concentration during the passage of Hurricane Irene (2011) over Chesapeake Bay: the shallow shoals in the mid Bay and the area around the mouth of the estuary. A coupled ocean wave sediment transport model is used to investigate mechanisms driving sediment resuspension and transport during the storm. The model reproduces the observed spatial variations of suspended sediment concentration and surface wave heights in the estuary and shows that both wave- and current-induced shear stresses are important in stirring bottom sediment. In the mid-Bay region, large wave-induced shear stress causes sediment resuspension on the shallow shoals, while wind-driven currents advect the suspended sediment downstream. Around the mouth of the estuary, the combined action of large waves and strong outflows produces high suspended sediment concentration, resulting in the export of similar to 0.8Mt of estuarine sediments to the shelf. The storm-induced sediment resuspension and export could be an important term in the sedimentary budget of an estuary. Plain Language Summary Episodic tropical storm events are important drivers of sediment resuspension and transport in the coastal ocean. The deposition and erosion of the sediments during these extreme weather events may affect stability and strength of seafloor and the local biological community. Despite its importance, the mechanisms controlling sediment resuspension and transport during storms are poorly understood. Here we use a coupled ocean wave sediment transport model to investigate mechanisms driving sediment resuspension and transport during the passage of Hurricane Irene (2011) over Chesapeake Bay. The model reproduces the observed spatial variations of suspended sediment concentration and surface wave heights in the estuary and shows that both wave- and current-induced shear stresses are important in stirring bottom sediment. The combined action of large waves and strong flows led to a large export of estuarine sediments to the shelf, with the total loss of similar to 0.8Mt of sediments over the duration of Hurricane Irene. These results suggest that storm-induced sediment resuspension and export could be an important term in the sedimentary budget of an estuary.