FLOOD INUNDATION AND DAM BREAK ANALYSIS FOR DISASTER RISK MITIGATION (A CASE STUDY OF WAY APU DAM)

This paper presents a numerical modeling to simulate flood inundation and dam break analysis of Way Apu dam for an emergency action plan (EAP), by considering EAP guidelines for ICOLD (International Committee on Large Dam). The Way Apu dam, located in Way Apu River, Maluku, Indonesia is a multi-purpose dam constructed mainly for irrigation, hydropower, water supply, and flood control. Therefore, the dam's outflow discharge needs to be analyzed, due to the large amount of rainfall in eastern Indonesia. Thus, there is a need to analyze flood inundation mapping and dam break simulation in a bid to identify the flood mitigation risk zone and early warning system, within the downstream area of Way Apu dam. In this study, the flood inundation mapping and dam break simulation were analyzed using HEC-RAS 5.0.7. The analysis results of flood routing generate the outflow peak discharge reduction over spillway were 7.36 % (Ten years return period discharge, Q10) and just 2.14% (Probable maximum flood discharge, QPMF), indicating the simulation results of Hec-Ras 5.0.7 model for conditions with or without dam break did not show significant difference in dam's downstream area. According to these results, 6 sub-districts are affected by the flood (Grandeng, Waeleman, Wanakarta, Waenetat, Debowae, Mako) with a maximum flood height range between 1-2.5 m (Q10) and 2.9-4.2 m (QPMF). The simulation results of arrival time also showed the estimation of evacuation time for QPMF ranges from 6 - 12 hours.