Hurricanes pose major threats to coastal communities and sensitive infrastructure, including nuclear power plants, located in the vicinity of hurricane-prone coastal regions. This study focuses on evaluating the storm surge and wave impact of low-probability hurricanes on the lower Delaware Bay using the Delft3D dynamically coupled wave and flow model.
The model comprised Overall and Nested domains. The Overall model domain encompassed portions of the Atlantic Ocean, Delaware Bay, and Chesapeake Bay. The two-level Nested model domains encompassed the Delaware Estuary, its floodplain, and a portion of the continental shelf. Low-probability hurricanes are critical considerations in designing and licensing of new nuclear power plants as well as in establishing mitigating strategies for existing power facilities and other infrastructure types.
The philosophy behind low-probability hurricane modeling is to establish reasonable water surface elevation and wave characteristics that have very low to no probability of being exceeded in the region. The area of interest (AOI) is located on the west bank of Delaware Bay, almost 16 miles upstream of its mouth. The model was first calibrated for Hurricane Isabel (2003) and then applied to synthetic hurricanes with very low probability of occurrence to establish the storm surge envelope at the AOI.
The model calibration results agreed reasonably well with field observations of water surface elevation, wind velocity, wave height, and wave period. A range of meteorological, storm track direction, and storm bearing parameters that produce the highest sustained wind speeds were estimated using the National Weather Service (NWS) methodology and applied to the model. Simulations resulted in a maximum stillwater elevation and wave height of 7.5 m NAVD88 and 2.5 m, respectively, at the AOI. Comparison of results with the U.S. Army Corps of Engineers, North Atlantic Coastal Comprehensive Study (USACE-NACCS) storm surge values at the AOI demonstrates that the estimated elevation has an annual exceedance probability of less than 10−4.
Author: Mehrdad Salehi- Sargent & Lundy