Dam break flood risk assessment and mapping for the Nyagak 111 dam

Abstract

Nyagak III dam is located in Zombo district, west Nile along the Nyagak River. Over time, dams have been known to break and cause immense damage on both people and property due to the resultant floods since dams hold a considerable amount of water behind them. The purpose of this study is to carry out a flood risk assessment as a result of dam break of the Nyagak III dam and to determine the extent of the risk associated with the floods. Various dam break scenarios were determined and also possible breach parameters were obtained. HEC HMS was used for the hydrologic modelling while HEC RAS software was used for the hydraulic analysis and flood mapping which was done using the RAS Mapper tool within HEC RAS software with the help of ARC GIS. Flow hydrographs were obtained along with flood maps showing both depth and Velocity varying along the catchment for both a sunny day and hydrologic events.