The success of living shoreline restoration projects in response to hurricanes, Nor’easters and coastal storms requires a better understanding of how living shoreline structures reduce the impact of wind waves and storm surges on marsh edges in estuaries and bays. Along the shorelines in the Chincoteague National Wildlife Refuge, oyster reef living shoreline projects were constructed by US. Fish and Wildlife Service (USFWS), The Nature Conservancy, and Virginia Marine Resources Commission after Hurricane Sandy to restore salt marsh and adjacent uplands. U.S. Geological Survey (USGS) and Northeastern University, in collaboration with USFWS, conducted field measurements of waves, currents, and sedimentation at multiple locations protected by the living shoreline structures (oyster castles) and at controlled locations without structures for two winter months in March – April 2019. Wave characteristics (wave height and wave period) were measured by wave gages with sampling frequency at 10 Hz every 30 minutes. Current velocity was measured by Acoustic Doppler Velocimeter (ADV) and tilt current meters (TCMs) at the shallow-water project area nearshore and the deep-water offshore locations. Sediment deposition or erosion from bed were measured using sediment traps and tiles during the monitoring period.
Results/Conclusions
Field measurements of waves, currents and sediment accumulation were used to calibrate and validate the Boussinesq wave model FUNWAVE-TVD and the Delft3D-SWAN model, which was used to assess the wave height attenuation and tide/wind/wave-driven currents with and without living shoreline structures at local and project scales. Sediment transport and morphological dynamics (sediment deposition and erosion) were simulated by the Delft3D model (Delft3d-FLOW and Delft3d-MOR) by coupling with the Delft3D-SWAN model that computes wave energy dissipation caused by bottom friction, wave breaking and vegetation effects as well as wave-current combined bottom shear stresses and the advection and diffusion of the sediment during the winter storm period. The model results of waves, currents and sediment deposition/erosion were tested against field measurements. Preliminary results indicate that living shoreline structures tend to be effective in reducing wave and current energy when structures are emergent (exposed). The effectiveness diminishes when structures are deeply submerged. The integration of short-term field monitoring with long-term numerical modeling is an effective tool to assess the performance of nature-based features. This is an abstract and does not necessarily reflect USGS policy.