The impact of offshore waves and vegetation on the sediment budget in theVirginia Coast Reserve (VA)

The possible for fast coastline modification in the face of sea-level rise or other stressors is alarming, since coasts are often densely populated and support valuable infrastructure. In addition to coastal submergence, nutrient- and turbidity-related water pollution is a growing concern for coastal wetlands. Previous studies found that suspended sediment concentrations (SSCs) of coastal wetlands acts as a first-order indicator of their sustainability, but precise controls on SSCs are poorly understood. In this study, we focus on the Virginia Coast Reserve Long Term Ecological Research (LTER) site, USA, where we apply numerical modeling (Delft3D-SWAN) and subsequent analyses to determine SSCs and their feedbacks that direct the wetland system to different landscape structures. In particular, we consider two important controls on SSCs: vegetation and ocean waves. We find that salt marsh, seagrass and offshore wave energy play a morphodynamic role in coastal wetlands by altering water residence time and increasing the volume of sediment retained in the bay. The reduction in the tidal prism decreases SSC export out of the bay via the tidal inlets. We find that alongshore currents can enhance sediment concentrations by importing fine sediments from inlets updrift, thereby coupling different wetland environments. We simulate the effect of different future wave climates scenarios, which can help evaluate the effect of different restoration strategies within the VCR.