HDOT Climate Resilience Action Plan | May 2021

as repair and reconstruction interventions, to understand better wildfire events on the network and anticipate probable future consequences, including repair cost estimates. Asphalt material is sensitive to temperatures and can be damaged in a wildfire. Moreover, due to the composition of this material, in very intense temperatures, asphalt can ignite and allow wildfires to spread along and across roads. A.8 LAVA FLOW » Recommendation A.8-1. When evaluating existing prioritized assets (i.e., those in Zones 1 through 3 in the Hawai‘i District and in Zone 1 in the Maui District), HDOT should evaluate the level of network redundancy to allow alternative access to areas served by the network, and improve redundancy if this level is found to be inadequate. Lava flow diversion strategies may be additionally considered. The assessment of network redundancy and lava flow diversion strategies should also be considered when conducting major improvements to existing State highways or constructing new assets in the areas most exposed to lava flow hazards. » Recommendation A.8-2. When an eruption occurs, the USGS HVO estimates the probable paths of lava flow using DEMs representing the topographies of volcanoes, enabling them to identify the steepest descent paths, and broad inundation zones defined by historical lava flow path data. The HVO also estimates lava flow travel times based on the advance rates of active flows and those of earlier flows in the same area (USGS HVO, 2020). During eruptions that require the activation of an EOC, the information generated by the HVO can be accessed by State agencies through the activated EOC. HDOT should consider developing and implementing a process to enable direct communication with the EOC and the HVO to identify assets along the State road network that may be affected by lava flows. This development should review communication during past emergencies, including the eruption of Kīlauea in 2018. » Recommendation A.8-3. HDOT should assess the effects of previous lava flows on the highway network, identifying common and recurring impacts, leading to improving the estimation of probable future consequences. » Recommendation A.8-4. This assessment should also consider seismic hazard events that have occurred in combination with past lava flow events. These combined events can result in significant damage to roadway assets. » Recommendation A.8-5. Underground voids created by lava tubes are hazards associated with active and inactive volcanic zones and lava flows. During the lava flow event of 2018, field crews used ground- penetrating radar to identify the locations of large voids that posed a potential hazard on State highways. These potential hazards were successfully identified in the Puna District of the Big Island, and HDOT subsequently undertook appropriate countermeasures, such as road closures, to protect the traveling public. There is a need to continue collecting field data to identify voids in other locations. This information can be used to complement the results of this exposure assessment and future risk analyses. » Recommendation A.8-6. HDOT should also assess other types of volcano-related hazards, including pyroclastic flows, air-fall tephra, and volcanic gases, along with their potential impacts on highways and personnel.

( A-6 ) HAWAI ‘ I HIGHWAYS | CLIMATE ADAPTATION ACTION PLAN