HAKOU v3: SWIMS Hurricane Inundation Fast Forecasting Tool for Hawaii

INTRODUCTION: U.S. Pacific Island coastal communities are extremely vulnerable to tropical cyclones. A powerful hurricane or typhoon can increase water levels and generate large waves impacting island coasts, causing coastal inundation and loss of infrastructure and life. While the complexity and accuracy in modeling coastal inundation continues to increase, most numerical models were conceived and tested primarily for U.S. mainland application. Developing methodologies to analyze accurately hurricane/typhoon waves and storm surge, and their interaction with island coasts, including coastal reefs, is the goal of SWIMS. Pacific Land-Ocean Typhoon Experiment (PILOT) and SWIMS have worked cooperatively toward improved measurements and modeling of storm waves and inundation on island coasts. PILOT has collected coastal processes and meteorological data under hurricane and high-wind conditions in Guam, Hawaii, Saipan, and the U.S. Virgin Islands. Wave and water level data from PILOT are then used by SWIMS, which serves to evaluate and extend existing models by developing new capabilities and links between models. HAKOU v3 is a SWIMS framework that estimates hurricane flooding risk for the Hawaiian islands of Kauai and Oahu by performing dynamic and fast evaluations of waves, surge, and inundation for approaching hurricanes (Smith et al. 2011). OVERVIEW: HAKOU employs a database of storm response to quickly forecast potential inundation risk when a storm threatens Hawaii. The database was generated from proven highresolution wave and surge simulations covering the range of hurricanes expected to impact the islands. Hurricanes are characterized by five simple parameters: landfall location, angle of approach, minimum central pressure, forward speed, and radius of maximum winds. The database is then used to forecast quickly potential waves, surge, and inundation by employing responsesurface surrogate modeling. Specifically, HAKOU calculates three different outputs: (1) maximum significant wave height, (2) maximum still water level, and (3) maximum wave runup level. HAKOU can perform either a deterministic assessment of a single hurricane track or a probabilistic assessment based on the error cone of possible tracks and forecasts. HAKOU provides deterministic predictions in seconds and probabilistic predictions in minutes. Additionally, inundation lines can be saved as shapefiles for viewing in GIS and as KML files for uploading to Google Earth.