Modeling of hurricane surge and waves in the built environment:

This report summarizes the proceedings and outcomes of the third Hurricane Ian Workshop, held on September 5, 2025, in Alexandria, Virginia. The purpose of the workshop was to explore the state-of-the-art in numerical modeling of overland flow in the built environment, focusing specifically on the hazard variables of surge, waves, and currents that critically affect structural integrity during hurricane landfall. The scope included an examination of model complexities and accuracies, ranging from time-averaged models like WHAFIS (used for flood insurance studies) to highly resolved, time-dependent models like OpenFOAM (Open Field Operation and Manipulation) and Delft3D-FM (Delft3D-Flexible Mesh Suite), and their application to events like Hurricane Ian. The conclusions/recommendations synthesized from the discussions resulted in three high priority actionable items intended to yield advancements in overland flow prediction: (1) preparation of a comprehensive, state-of-the-art review paper on existing overland flow models; (2) initiation of an inter-model comparison study for a fixed domain (e.g., Estero Island) with common boundary conditions to identify modeling gaps; and (3) a scoping study for largescale laboratory validation experiments to benchmark numerical model performance against real-world, multi-hazard phenomena.