Wave Effects on Hurricane Storm Surge Simulation

Abstract

Hurricane storm surge depends on the tidal stage, barometric pressure, Coriolis effect, wind stress, and wave forcing, as well as the local bathymetry. In the past, storm surge numerical models, such as Sea, Lake, and Overland Surges from Hurricanes (SLOSH), neglect wave forcing components to conserve computational efficiency. However, since hurricane wind, storm surge, and waves are coupled phenomena, numerous situations necessitate the inclusion of waves' effects to more correctly model hurricane storm surge. This paper describes the result of a collaborative effort by the National Institute of Standards and Technology (NIST), the National Oceanic and Atmospheric Administration (NOAA), and the University of Florida (UFl) to incorporate a wave model into the SLOSH model to extend its capability for storm surge simulation. A two-way coupling methodology was developed to incorporate two wave forcing components, that is, set-up from wave stresses and mass flux transport, into the SLOSH model. The aim was to better understand the relative contribution of each effect and their relationship to both storm strength and bathymetry. To this end, numerous simulations with different forcing variations (wind-stress only, wind and wave stresses, and wind and wave stresses with mass flux transport) were performed. The wind stresses used for the simulations were based on three hurricanes with different intensities, and the simulations were conducted for two basins with contrasting bathymetry in Florida (shallow and steep slopes). The results show that the impact of wave set-up and mass flux to storm surge levels varies between locations – even for the same storm in the same basin – proving that the interaction between the wind and wave forcing components is indeed complex. On average, however, the addition of the wave set-up and mass flux raised the maximum storm surge levels 10 to 30 percent, although isolated positions experience increased well above 100 percent.