Prediction of Storm Surges and Wind Waves on Coastal Highways in Hurricane-Prone Areas

Abstract

A recent study reveals that more than 60,000 miles (>96,500 km) of coastal roadways are in the 100-year floodplain in the United States and vulnerable to the attacks of water surges and storm waves generated by hurricanes. Mitigating the effects of coastal flooding requires accurate predictions of the destructive hydrodynamic forces. This study demonstrates a methodology for integrating state-of-the-art storm surge and wave prediction models as an effective tool for engineering design of coastal infrastructure and facilitation of hurricane emergency management. The methodology has the capability of resolving complex geometry and topography typical of coastal road flooding. The surge model incorporates moving shoreline conditions associated with flooding and allows for nonlinear interactions among astronomical tide, storm surge, and wave setup. The wave model takes into account the unsteadiness of wind forcing, currents, and water levels. A historical hurricane event is simulated for the landfall of Hurricane Georges (1998) on the north coast of the Gulf of Mexico. Good agreement between the modeled and measured surge hydrographs in Mobile Bay, Alabama, has been found. The advanced surge model (ADCIRC), coupled with the wave model, successfully simulates the inundation and measured high water marks along two highways adjacent to the bay. The third-generation wind wave model (SWAN) coupled with the hydrodynamic model reveals the temporal and spatial variability of wave heights and wave periods in the Mobile Bay estuary and on the flooded highways. Numerical experiments were carried out to examine the response of the estuary to various forcing agents, including the offshore surge hydrograph, local wind forcing, and wave thrust.