The State of Hawaii Statewide Coastal Highway Program Report

Small Pacific Island communities are vulnerable to sea level rise and high energy wave environments. Our study looks at the Hawaiian Islands, situated in the North Pacific Ocean, which is of particular interest given the high population density and strategic importance to the United States. A “State of Hawaii Statewide Coastal Highway Program Report” was delivered on August 21, 2019 to the State of Hawaii Department of Transportation Highway Division to assess and rank the susceptibility of the State of Hawaii coastal roads due to ocean hazards. Throughout the State of Hawaii, 302 mileposts on the islands of Oahu, Kauai, Maui, Molokai and Hawaii, are identified and assessed, due to their close proximity to the ocean. We rank the susceptibility of the State of Hawaii coastal roads using a new index methodology called the Coastal Road Erosion Susceptibility Index (CRESI), which considers the principal factors that determine coastal erosion and road degradation. CRESI is developed from prior studies that consider coastal erosion without a specific focus on road infrastructure. As such, it represents a novel engineering tool of specific relevance to those in charge of managing and maintaining coastal road networks. CRESI considers elements of vulnerability and hazards, but it does not yet represent a risk measure. Since the report, there are ongoing efforts regarding traffic and ocean hazards that are leading to improved versions of the CRESI index. Our results show the rankings of 302 mileposts for the improved version of the Coastal Road Erosion Susceptibility Index (CRESI) using the Ocean Hazard Classification Scheme (OHCS) that we also developed for the report, and how transportation can be included.