On the Receding of Storm Surge along Louisiana's Low-Lying Coast

Severe damage from storm surge often occurs over low-lying, small slope land subject to inundation. The extent of the environmental damage depends on the flooding as well as how long the flood water remains - or how long the receding of the surge takes. An investigation of storm surge impact to the coast of Louisiana is conducted using the state-of-the-art finite-volume coastal ocean model, FVCOM (CHEN et al., 2003). All nonlinear terms are included in FVCOM's governing 2D equations, and hurricane simulations in this paper are forced by tides and wind stress. An application of the model to Hurricane Rita's storm surge event is described, and data along the Louisiana-Texas coast in September 2005 used for model validation. USGS surge data covering Hurricane Rita, our own data covering Hurricane Gustav (September 2008) and our modeling results were combined to study the receding stage of surge waters. We quantify typical longer term hurricane-induced inundation patterns, for different locations affected by the surge. We show that the surge outflow, which peaks at about 24 hours after landfall, takes much longer than the initial flooding due to different dynamics over coastal passes and floodplain near the shoreline. Whereas flooding occurs along large parts of the shoreline (decreased bottom friction results in a brief, vast landward transport of water), the surge flows back to the Gulf constrained by the existing channels, and surge waters flow out of the region's major coastal passes in a plume-like pattern.