U.S. completes dam-break studies of Hawaii dams

The Corps of Engineers has completed ten detailed dam-break studies of dams throughout Hawaii identified as being of special concern primarily due to downstream urban development.

Sen. Daniel Inouye, D-Hawaii, secured $2 million in funds for the studies following the 2006 failure of Kaloko Reservoir Dam on the island of Kauai, in which seven people died. (HNN 10/30/06) The Corps initiated the studies in January 2007, choosing the dams from a list prepared by the Hawaii Department of Land and Natural Resources’ Dam Safety Program.

The Corps evaluated various hydrologic and dam failure scenarios, and analyzed hydraulics that resulted from maps of downstream areas that could be adversely affected. Several consulting firms assisted the Corps in the work, including Tetra Tech, PB Americas in joint venture with Northwest Hydraulic Consultants, SSFM International in joint venture with WEST Consultants, and Oceanit Laboratories.

The reports cover engineering models of possible dam failures due to extreme loading scenarios. The state said hazard maps included in each report could be used to assist in classifying a dam’s hazard potential but added they are not evacuation maps.

The Corps transmitted reports of the studies to the Department of Land and Natural Resources for: Nuuanu Dam No. 4 and Wahiawa Dam on Oahu; Twin, Waita, Elua, Aepo, Puu Lua, Reservoir 24, and Upper Kapahi reservoirs on Kauai; and Kualapuu Reservoir on Molokai. It expects to complete the study of an 11th dam �- Halamanu Reservoir 21 on Maui — in March. The department posted the reports on its website, http://hawaii.gov/dlnr. The link address is http://hawaii.gov/dlnr/reports-1/dam-break-studies.

The State Dam Safety Office will use the reports in following up with dam owners and local emergency preparedness agencies, State Dam Safety Officer Edwin Matsuda said.

The department’s Hawaii Inventory of Dams listed 133 dams: 53 on Kauai; 16 on Oahu; 51 on Maui, Molokai, and Lanai; and 13 on the island of Hawaii. The state categorized 75 dams as high risk, 21 as significant risk, 20 as low risk, and 17 as dams of an undetermined risk.

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