Hydrologic Modeling for Dam Break Analyses in Hawaii

Abstract

This paper is one of several being presented during a special Technical Session dedicated to recently completed dam break and flood hazard mapping analyses that were performed throughout the State of Hawai‘i on behalf of the State Department of Land and Natural Resources and the Honolulu District U.S. Army Corps of Engineers. Basin hydrology, dam break and downstream flooding assessments were conducted for eleven reservoirs located in the State of Hawai‘i. This paper focuses on procedures used to develop consistent basin hydrologic information required for these studies. The overall hydrologic approach, data preparation and analysis; model parameter estimation; model testing, calibration and application methods; and key results are summarized, herein. When work began on the dam break studies in January 2007, there were very few hydrologic reports found that contained the hydrologic data, and types of detailed information required for the basins that were to be analyzed for this project. This paper provides a framework for developing hydrologic models designed to provide reliable rare storm event rainfall and runoff information in a variety of locations and settings throughout the State of Hawai‘i. Hydrologic data needs are discussed along with sources where available data may reside. Discussions of methods used to develop information for ungaged basins (basins with no rainfall or runoff records) are presented along with methods used for developing and testing the hydrologic models, including hydrologic parameter estimating procedures. A summary of adopted hydrologic model parameter values and a discussion of lessons learned during the hydrologic modeling work are provided. Background Beginning in February and lasting into early April 2006, the Hawaiian Islands experienced a series of unusually severe rainfall events that caused flooding throughout the State of Hawai‘i. During this period, the privately owned Kaloko Dam on the northeast side of the island of Kaua‘i failed, sending a floodwave of (%)