Multi-Hazard Mitigation Plan: 18. Risk Assessment

Home

Chapter 18:Risk Assessment The 2006 Kiholo Bay Earthquake had a relatively minor impact on the roads and bridges in Hawaii County. Although rock and soil slides in cuts above roadways were numerous, damage to road embankments and pavements was less prevalent, with a few exceptions (Figure 18-12). The most dramatic of these was the collapse of half of the roadway at Mile 35 on Highway 19 near Pa`auilo,resulting in the closure of one lane of traffic (Figure 18-13). This was caused by failure of a 20-foot high embankment and rock wing wall on the approach to a concrete girder bridge. The cast-in-situ concrete girder bridge is supported on rock wall abutments. The bridge suffered no damage but the adjacent embankment failed. The wing wall consisted of mortared rock and was approximately 14 inches thick. Because of the lack of redundancy in the highway system on the Island of Hawaii, road closures due to rockfalls, landslides or embankment slope instability can have a significant effect on emergency response and economic recovery efforts. For a number of hours after the earthquakes, the area of North Kohala, including the town of Hawi, was cut off from the rest of the island because of road closures on Highways 250 and 270, the only access roads to this region. Fortunately, the rockfalls and landslides caused by these earthquakes could be cleared relatively easily, and all roadways on the Island of Hawaii were open to at least one-lane traffic within two days of the earthquakes. 18-29 Hawaii County Multi-Hazard Mitigation Plan