Dam break analysis of Temenggor Dam using HEC-RAS

Abstract

Embankment dam is commonly built in Malaysia as it provides benefits to the local population, mainly agricultural activity and flood control measures. However, its massive potential energy reservoir would impose risk of sudden containment breach leading to loss of life and property at inhabited downstream area. This paper deemed to provide a dam break analysis of Temenggor Dam to generate breach hydrograph and inundation map as a result of dam break event under piping and overtopping failure. The Hydrologic Engineering Center's River Analysis System (HEC-RAS) is capable to model 1-dimensional (1-D) and 2-dimensional (2-D) dam failure event by utilizing hydrological and terrain information generating unsteady-state flow simulation of the dam breach. The process for gathering and preparing data, estimating breach parameters, creating one dimensional and two-dimensional unsteady-flow model in HEC-RAS, performing a dam failure analysis for two dam failure scenarios and mapping the flood propagation are outlined in this paper. From 1-D analysis, it is found that the breach flow of Temenggor Dam failure can achieve 281,588 m3/s for piping failure and 331,030 m3/s for overtopping failure. 2-D analysis' breach flow attained 268,341 m3/s and 328,869 m3/s for piping and overtopping failure, respectively. Furthermore, the expected arrival time of flood wave at selected locations also presented in this paper. 1-D model produced comparable breach hydrograph result of Temenggor Dam against 2-D model with the advantage of significantly shorter simulation time requirement. However, 2-D model able to generate inundation map due to dam failure in wider area which can provide insight of flood hazard risk level and contribution for emergency action plan development.