CHARACTERIZING SLOW AND RAPID PHASES OF INUNDATION TO ASSESS SEA-LEVEL RISE IMPACTS

Globally, sea-level rise (SLR) threatens nearly one-third of the world’s population by direct inundation, salt water intrusion, increased coastal erosion, and drainage problems. To better communicate these risks to the public, we calculate a key transitional elevation that distinguishes between slow and rapid phases of modeled inundation, and correlate the elevation with time using Vermeer and Rahmstorf (2009) B1, A2, and A1FI SLR curves. For the north shore of O‘ahu, Hawai‘i a rise in sea-level exceeding 0.60 m above mean higher high water triggers rapid flooding shortly after mid-century. To simulate the impacts of SLR for both phases of inundation we use a high resolution 2007 USACE (U.S. Army Corps of Engineering) LiDAR digital elevation model (DEM). Our analysis accounts for the joint uncertainty of the SLR predictions and the vertical uncertainty of our LiDAR data. Across the transition point, areas of potential inundation increased from 2.8% for all SLR scenarios to 14.2%, 18.6%, and 26.4% for the B1, A2, and A1FI scenarios respectively. Vulnerable areas include a series of wetlands, bare earth, and the coastal strand that provide native and endangered species habitats and drain the surrounding developed community during storm events. Planners have approximately 50 years to implement adaptation strategies in advance of the rapid phase of inundation.