HDOT Climate Resilience Action Plan | May 2021

Observed Conditions

Analysis of Recurrence

Apply Design Policy APPLIED DESIGN

Based on Historical Conditions

Based on Estimated Future Conditions

Estimate Changing Future Conditions

Design for Risk

Determine Consequences

Estimate Life Cycle Costs

Figure 1 Current Practice vs

Future Resilience Practice

A PROACTIVE PERSPECTIVE ON MITIGATING RISK Several recent extreme weather events have resulted in significant impacts to Hawai‘i’s highway system, and in some cases, the resulting impacts caught HDOT unaware. This is partly because the impacts to highways were much greater than had been expected when the road was designed. It has not been common practice to examine future possible risks to above-normal extreme weather effects. However, providing resilient infrastructure that takes into consideration expected environmental conditions is becoming a greater concern throughout the country. HDOT recognizes that it does not have all the information it needs to adopt such an approach. Efforts undertaken by others and documented in this Action Plan present a positive first step, but more work is needed at a more refined level to identify where adaptation investments are most critical and what it will take to create a highway network that is resilient to the hazards that may affect Hawaii. In this Action Plan, HDOT has committed to better defining the risks from extreme weather and climate change, develop the information it needs to be more proactive in its assessments, and take action to eliminate or reduce the impacts before they occur (Figure 2). A key element of this effort will be to take a closer look at conditions along the highway network and reduce or eliminate the unknowns and uncertainties associated with expected climate change-related hazards. Such an effort will require a more extensive program to accurately define specific locations on the highway network that have considerable risk to climate change-related disruptions and that lead to proactive adaptation investment. The identification of some risks is currently being conducted by State partners, including the University of Hawai’i, which is identifying coastal risks at a more refined level, generating data that will be helpful for HDOT in making more fully informed decisions. Other required data could be generated through collaboration with other State and Federal partners. Field reviews and engineering assessments will also provide the necessary information required to assess the immediacy of risks/impacts and the timing for when potential impacts may need to be addressed in investment programs.

Values of design input factors such as mean higher high water, precipitation return periods, seismic risks, landslide potential, and similar measures are determined directly from field observations and assessments of existing or past conditions. Research efforts conducted through agencies such as NOAA, USGS, the Federal Highway Administration (FHWA), the Transportation Research Board, and the American Association of State Highway and Transportation Officials (AASHTO) or by HDOT and the University of Hawai‘i contribute to the body of knowledge that supports project decision-making. However, 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 may 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. It represents a different approach, and there are many uncertainties associated with the projections of climate variables, and the strategies and designs developed in response need to be more flexible and adaptive to changing environmental conditions. Changing the perspective from one that is based on historic trends and analyses to one that is more oriented to projected changes is an important underlying theme of this Action Plan. The information contained in the Exposure Assessments report of this Action Plan outlines how future conditions are expected to be different from past conditions and thus provide a general basis to make future-oriented decisions. Figure 1 illustrates the different perspective that is needed to lead to better and more adaptive investment decisions for transportation assets in Hawai‘i. The three gray boxes leading into applied design identify how elements of risk are determined through current practices, looking backwards in time. In contrast, the colored boxes identify the steps toward incorporating a future-looking perspective. By addressing inherent uncertainties, such an adaptive approach can facilitate decisions that better consider how future conditions could affect an asset and its users, resulting in better and more resilient investments. The process for how this works at the project level is defined in Next Steps section of this Action Plan. Such a shift in approach is a critical capability, which is an underlying basis for much of this Action Plan.

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