Hurricane Flood Insurance Study for the Hawaiian Islands

In order to implement the FEMA "Map Modernization Project" through the incorporation of recent advances in coastal storm surge and wave-height modeling technologies, a new study was commissioned to update the digital Flood Insurance Rate Maps (FIRMs) for the Hawaiian Islands. A complete update of the coastal modeling was carried out starting with a new storm surge study. The Advance Circulation Model (ADCIRC) was used to model storms and develop storm surge values along the south shore of each island. The Empirical Simulation Technique (EST), developed by the U.S. Army Corps of Engineers (USACE), was used to determine the stillwater frequency curves for the 10% (10-year), 2% (50-year), 1% (100-year), and 0.2% (500-year) annual chance stillwater elevations. Updated stillwater elevations were utilized in the Coastal Hazard Analysis Modeling Program (CHAMP) to develop wave height and wave run-up analyses. Wave set-up for linear slopes was calculated using the Direct Integration Method (DIM). Wave set-up on reefs was determined using the methodology outlined by Gourlay (1996). The new FEMA coastal guidelines were used to determine wave run-up. The results of these analyses are used to map new coastal flood hazards around the islands using automated tools in a GIS environment.