Simulating Waves and Water Levels in the Chesapeake Bay during Hurricane Isabel Using a Coupled Wave-Current Model

During a storm, surface waves can profoundly modify the surface and bottom turbulent boundary layer, and mass and momentum transports, resulting in a change of current velocity profile as well as water levels. Many shallow water wave models are designed for the wave transformation in the near-shore process, or applied during fair weather conditions without considering major input of energy source, or do not include the interaction with the change of water level, current velocity and nonlinear dissipation due to wave-current interaction. In order to take these effects into account, the three dimensional hydrodynamic UnTRIM model is dynamically linked with the UnK wave model. The UnK model is a 3^rd generation spectral wave model which solves the action balance equation on unstructured grids. This coupled model is used to investigate the effects of surface waves on the storm surge in York River estuary during the extreme conditions of hurricane Isabel (2003). A rare dataset including wind speed and direction, wave height and period, and directional energy spectra collected in the York River during Hurricane Isabel is used for examination. During the peak surge period of Hurricane Isabel, the surface wave was propagating with the flood currents and the significant wave height was as high as the surge height, reaching up to 1.6 meters. It is shown that hurricane-induced surface wave height and period was adequately simulated by the coupled model. The wave effects can strongly modify the storm surge characteristics and linear superposition of current and wave model can not explain the phenomena unless the wave-current interaction mechanism is specifically included.