HDOT Climate Resilience Action Plan | May 2021

The Urgency: Why We Must Act and Change Current Practices 2

THE NEED FOR A RESILIENT HIGHWAY SYSTEM HDOT is responsible for the condition and performance of approximately 971 (linear) miles of highways on 6 islands within the State. Just over 456 miles of this network is part of the National Highway System (NHS). The effective management of these NHS highways is a top priority for HDOT because of their vital contribution toward community access, economic prosperity, national security, and overall mobility (HDOT 2019a). The configuration of the State Highway Network reflects the terrain and geography of the State. Belt roadways on low-lying coastal areas typically encircle each island, while steep central mountain ranges a few miles inland limit the number of cross- island routes. These roadways are critical for each island given the limited alternatives for accessing many island communities. Unfortunately, this configuration makes the highway network especially vulnerable to natural hazards. Shoreline change, coastal erosion, and storm surge compromise the State’s coastal highways. In addition, the roadways that pass through mountainous terrain are susceptible to natural weathering, erosion, and rockfall where the volcanic rock slopes and cliffs have been excavated to construct the roadways. Several recent extreme weather events have resulted in significant unanticipated impacts to Hawai‘i’s highways. The severity and increased frequency of these events are attributed to weather or climate change hazards that are not typically effectively addressed in traditional highway design methods. Applied design standards are based on the analysis of past conditions; however these are proving insufficient, as many states nationally are coping with unanticipated risks to safety and extensive damage to highway infrastructure. Traditional design standards will need to be adjusted to address the effects associated with climate changes and better reflect future risks to the highway system.

HDOT recognizes it is important to increase the resiliency of highway infrastructure by incorporating future climate change considerations into HDOT project design, operations, maintenance, and programming and budgeting. The intended result is improved infrastructure resilience to climate change hazards, reduced operation and maintenance costs, and reduced risk to public safety. A FUTURE UNLIKE THE PAST Climate change will result in environmental conditions that are different than those historically considered as a part of transportation project development and decision-making. Transportation planning and design, like most science-based technical disciplines, are dependent on research to develop best practices that often reflect how transportation facilities have responded to historic environmental conditions. Field measurements are made, summaries are created, statistical analyses are completed, and target levels are identified on which to make decisions (e.g. a 50-year storm event, etc.). Climate change shifts the perspective from past conditions as the only predictor of the future, to forward-looking analyses that consider projections of how the future could be different. Adopting such a forward-looking perspective has proven to be one of the greatest challenges associated with changing standard practice in state transportation agencies.

10 HAWAI I HIGHWAYS C L I MAT E ADAP TAT I ON ACT I ON P L AN