Multi-Hazard Mitigation Plan: 11. DamFailures

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Chapter 11:Hazard Analysis—Dam Failures c � 0 Critical Dams Dams Figure 11-1. Dam Inventory and Rating Following the 2006 Kiholo Bay Earthquake some damage occurred to dams and irrigation ditches in the Waimea-Kamuela area where recorded peak ground acceleration exceeded 1.0g (soil depths are greater in that region than along the rocky coast nearest the epicenter). At least two dams experienced cracks along their crests, while at least two others showed clear evidence of incipient slope failure on their embankments. The Pacific Disaster Center performed dam break simulations for Hawaii County Civil Defense. Two dams located above Waimea were drained after excessive seepage and "water boils" were observed five days following the earthquakes. The State Department of Land and Natural Resources had in place post-earthquake dam inspection procedures. The Hawaii Dam Safety Guidelines: Seismic Analysis & Post-Earthquake Inspections (Brandes, 2004) call for inspections of dams within 75 miles of the source of an earthquake of magnitude between 6 and 7. The U.S. Army Corps of Engineers undertook these comprehensive inspections. The U.S. Army Corps of Engineers (USACE) provided Hawaii State Civil Defense (HSCD) with completed documentation concerning the Statewide Dam Visual Conditions Survey in response to the Kiholo Bay Earthquake on October 15, 2006. Documentation includes electronic field inspection reports with corresponding photographs for 86 dams inspected by USACE between October 30 and November 8, 2006. HSCD asked Pacific Disaster Center (PDC) to develop a map viewer application to allow authorized users to view the documentation provided by USACE. PDC created (and will maintain) a password-protected map viewer that hosts and displays USACE data for persons authorized by HSCD to access 11-2 Hawaii County Multi-Hazard Mitigation Plan