MODELING COASTAL EROSION, GROUNDWATER INUNDATION, PASSIVE INUNDATION, AND WAVE INUNDATION UNDER HIGHER SEA LEVEL IN HAWAII

The State of Hawaii Interagency Committee on Climate Adpatation is investigating community vulnerability to sea level rise. We have developed modeling to provide the committee with assessments of exposure to coastal erosion, wave run-up, and flooding based on the IPCC model of sea level rise over the 21st Century. We model the exposure to coastal erosion using a hybrid equilibrium profile model (Anderson et al., 2015) that integrates historical rates of shoreline change with a Bruun-type model of beach profile translation. results are mapped in a GIS showing the 80%ile probability of erosion at years 2030, 2050, 2075, and 2100. Wave run-up is modeled on a topo/bathy LiDAR DEM using data from the 2013 JBLTX survey of the Hawaiian islands. We use XBEACH (Delft Hydraulics) to estimate inundation at higher levels during the same time periods by a 3 m Hs wave to represent a seasonal high swell event. XBEACH is used in the 1D mode with settings for a permeable substrate. We develop a gridded product of depth and velocity for use in a vulnerability analysis. DEM scenarios of sea level flooding, the so-called "bath tub" method, provide estimates of storm drain flooding and groundwater inundation. Combined, these impacts of sea level rise are used with FEMA Hazus software to estimate exposure and loss of upland assets.