A Basin- to Channel-Scale Unstructured Grid Hurricane Storm Surge Model Applied to Southern Louisiana

TLDR

Southern Louisiana’s low‑lying topography and extensive network of sounds, bays, marshes, lakes, rivers, and inlets make it highly susceptible to widespread hurricane‑induced inundation. The authors built a basin‑to‑channel ADCIRC unstructured grid model covering the western North Atlantic, Gulf of Mexico, and Caribbean Sea, applying realistic tidal and hurricane boundary conditions, refined overland resolution, wind fields adjusted for roughness and canopy effects, and parallel robust algorithms. The model accurately simulates storm surge, tides, and river flow, achieving a mean absolute error of 0.30 m for peak surge height in hindcasts of Hurricanes Betsy and Andrew.

Abstract

Abstract Southern Louisiana is characterized by low-lying topography and an extensive network of sounds, bays, marshes, lakes, rivers, and inlets that permit widespread inundation during hurricanes. A basin- to channel-scale implementation of the Advanced Circulation (ADCIRC) unstructured grid hydrodynamic model has been developed that accurately simulates hurricane storm surge, tides, and river flow in this complex region. This is accomplished by defining a domain and computational resolution appropriate for the relevant processes, specifying realistic boundary conditions, and implementing accurate, robust, and highly parallel unstructured grid numerical algorithms. The model domain incorporates the western North Atlantic, the Gulf of Mexico, and the Caribbean Sea so that interactions between basins and the shelf are explicitly modeled and the boundary condition specification of tidal and hurricane processes can be readily defined at the deep water open boundary. The unstructured grid enables highly refined resolution of the complex overland region for modeling localized scales of flow while minimizing computational cost. Kinematic data assimilative or validated dynamic-modeled wind fields provide the hurricane wind and pressure field forcing. Wind fields are modified to incorporate directional boundary layer changes due to overland increases in surface roughness, reduction in effective land roughness due to inundation, and sheltering due to forested canopies. Validation of the model is achieved through hindcasts of Hurricanes Betsy and Andrew. A model skill assessment indicates that the computed peak storm surge height has a mean absolute error of 0.30 m.