The salt marshes of Jamaica Bay, managed by New York City Parks and Recreation and the Gateway National Recreation Area (GNRA) of the National Park Service, provide critical ecosystem services. Hurricanes and extra-tropical storms are critical drivers of coastal wetland morphology due to their impacts on hydrodynamics and sediment transport, deposition, and erosion. However, the impacts of hurricanes on sediment dynamics and associated coastal wetland morphology in the northeastern United States are poorly understood. In this study, we used Delft3d modeling integrated with field measurements to examine the impacts of Hurricane Sandy on salt marsh morphology. Three domains (ocean, regional, and local scale) were set up for nesting computations. The local domain, covering Jamaica Bay, had a resolution of 10 m, enabling fine scale detection of wetland morphological change. Hurricane Sandy-induced winds, waves, storm surge, water circulation, sediment transport, deposition and erosion were simulated using the model. Observed surge from tide sensors, elevation change and accretion from Surface Elevation Tables (SETs) and feldspar marker horizons, and 137Cs and 210Pb-derived long-term accretion rates were used to calibrate and validate the model.
Results/Conclusions
The model results agreed well with field measurements. The model was successful in capturing the breach in the West Pond of the Jamaica Bay Wildlife Refuge, GNRA. Simulation results indicate that Hurricane Sandy resulted in substantial changes in the spatial patterns of sediment deposition and erosion compared to simulations without the hurricane. Waves were shown to play a critical role in salt marsh morphological change in Jamaica Bay, and vegetation was shown to enhance sediment trapping and reduce erosion. As a result, the impacts of Sandy will continue to influence sediment accumulation and accretion in the Jamaica Bay salt marshes.