Storm tide simulation in the Chesapeake Bay using an unstructured grid model

Hurricane Isabel made landfall near Drum Inlet, North Carolina on September 18, 2003 (UTC 17:00). Although it was classified as only a Category 2 storm (Saffir–Simpson scale), Hurricane Isabel had a significant impact on the Chesapeake Bay with a 1.5–2.0 m storm surge (above mean sea level), and was dubbed the “100-year storm”. A high-resolution unstructured grid model (UnTRIM) was applied to simulate storm tide in the Chesapeake Bay. The application of an unstructured grid in the Bay offers the greatest flexibilities in representing complex estuarine geometry near the coast and encompassing a large modeling domain necessary for storm surge simulation. The resulting mesh has a total of 239,541 surface elements. The model was forced by 9 tidal harmonic constituents at the open boundary and a wind field generated by a parametric wind model. A hindcast simulation of Hurricane Isabel captures both peak storm tide and surge evolution in various sites of the Bay. Model diagnostic studies indicate that the high surge occurring in the upper Bay regions was mainly caused by the forced southerly wind, whereas the offshore surge and both the northeasterly and southeasterly winds influenced the lower Bay region more significantly.