UH Manoa Department of Urban and Regional Planning Research Highlight: Summer 2020

This article highlights a study authored by Dr. Suwan Shen and Dr. Karl Kim. It focuses on transportation system vulnerabilities to tidal flooding by combining physical impacts and harm to socially-vulnerable groups. Transportation vulnerability is assessed in terms of roadways at risk and changes in accessibility due to flooding. The study shows potential impacts of sea level rise on transportation, and helps to prioritize zones for flood mitigation. The study authors are affiliated with the University of Hawaii at Manoa’s Department of Urban and Regional Planning and the National Disaster Preparedness Training Center.

Assessment of Transportation System Vulnerabilities to Tidal Flooding in Honolulu, Hawaii

Suwan Shen, Karl Kim

Abstract 

Tidal flooding, a tangible, present-day effect of sea level rise, has caused roadway damage and transportation system closures as well as delay, disruptions, and economic losses. There is a need for more research, understanding, and planning for the management of this threat to transportation services. Using data on tidal flooding, transportation networks, land use, and population characteristics, the vulnerability of transportation systems to tidal flooding is assessed for Honolulu, Hawaii. Accessibility measures coupled with population characteristics provide quantitative estimates of underlying exposures and vulnerabilities of travelers to disruptions. Using GIS and overlay mapping techniques, at-risk roadway segments are identified and Traffic Analysis Zones (TAZs) are ranked in terms of accessibility changes. Trips to work, school, grocery shopping, recreational activities, and emergency services are analyzed. In addition to identifying critical, at-risk facilities, the analysis includes the consideration of vulnerable populations, such as elderly, young, low income, and those with limited transportation options. Using a nonparametric, mean shift clustering method, TAZs are ranked and prioritized for potential mitigation actions accordingly. While 90% of TAZs have minimal impacts, several experience up to 100% accessibility reduction. High priority areas are located in Laie, Punalua, Kailua, Waimanalo, Hawaii Kai, and near Honolulu Harbor. In addition to transportation system planners, the analysis is useful to first responders, emergency managers, and others working to increase transportation system resilience. Designed as a flexible planning, decision-support tool, the approach could be adapted to plan for other types of hazards such as tsunamis or storm surge as well.

Please contact Suwan Shen at suwans@hawaii.edu for a copy of this article. Questions related to this article can also be sent to the email address provided.