Skip to main content

Dam Break Analysis Program

Project Description

In February 2006, the Hawaiian Islands experienced unusually severe rain showers that caused severe flooding throughout the state. The resulting heavy rainfall resulted in the failure of privately-owned Kaloko Dam on the Northeast side of the island of Kaua‘i.  The dam failure sent a floodwave of water and debris downstream that overtopped the Morita Dam, damaged Kuhio Highway, and swept away homes resulting in 7 fatalities.  This disaster resulted in a Federal Assistance program with the Department of Land and Natural Resources (DLNR) to re-evaluate the condition and awareness of the highest hazard dams throughout the state. In 2008, Oceanit analyzed dam break scenarios for those high-hazard dams-  Nu‘uanu Reservoir near Honolulu and Wahiawā (Wilson) Dam in the Kaukonahua Watershed of central Oahu. Analyses were required to evaluate the likely downstream inundation area in the case of a dam failure.

This project required: 

  • Acquisition of accurate topographic data and information, over a larger watershed area, for the development of  baseline information to assess existing dam status and project area characterics.
  • Performance of complex evaluations of various inflow scenarios, various dam failure scenarios, and mapping for resulting downstream inundation area hazards.
  • Coordination with the U.S. Army Corps of Engineers, the DLNR Dam Safety Office, and the City and County of Honolulu.

Oceanit's Actions:

  • Provided hydrological and hydraulic analyses for Probable Maximum Flood (PMF) events for a range of possible dam break scenarios.
  • Developed a computer model of the areas’ hydrology with each areas’ geometry to simulate a PMF flood event flooding.
  • Utilized both 2D & 3D hydraulic models to best stimulate and verfiy hydrologic results to model hydraulic conditions caused by a reservoir breach.
  • Calibrated and optimized model performance to produce stable accurate results by adjusting land roughness values, uneven stream profiles, and other model parameters. These set paramaters allowed for a sensitivity analysis to determine the most conservative estimate on the potential effects of a dam breach
  • Mapped the floodwave and debris flooding downstream from the dam breach with computer model results, which displayed the inundation harzard zones.
  • Given the hazard innundation areas resulting from possible dam failure scenarios, informed future mitigation plans could now be formulated.