The Delft3D Flexible Mesh Suite (Delft3D FM) is an open-source hydrodynamic modeling system created by Deltares to simulate storm surge and other coastal hydrodynamic processes. A key advantage of Delft3D FM is the robust, efficient, and stable mesh generation capability of the software. Combining this mesh generation technology with in-house expertise and detailed data for model initialization and wind/pressure forcing, the team at AIR Worldwide has created a Delft3D FM-based storm surge catastrophe model for part of Great Britain (England and Wales). This Great Britain coastal flood model captures storm surge risk from extratropical cyclones. Simulated historical surge events such as Storm Xaver (2013) and the North Sea Flood of 1953 will be shown, as well as modeled surge return periods. Finally, it should be noted that similar technology can be used for simulating tropical cyclone-induced storm surge risk in areas impacted by tropical cyclones.