Dam Breach Analysis Using HEC-RAS: A Case Study of Naumure Dam, Nepal

This study aimed to evaluate the potential dam breach scenario of the proposed Naumure Dam using the HEC-RAS model. Hydrological and meteorological data from the study area were used to calculate the probable maximum flood, serving as a hydrological input for the model. Geometric data such as reservoir area, inline structure, streamline, riverbank, and flow path were modeled using the HEC-RAS RAS-Mapper tool. Various parametric equations were employed to calculate the breach parameters, which were then input into the HEC-RAS 5.0.7 simulation model along with the input hydrograph. Subsequently, an unsteady flow analysis was conducted to direct the flood through each cross section of the river. The model yielded a maximum flow rate of 141,423.48 m3/s at the dam axis 3.8 hours after the onset of dam failure. The study area, which extended 31.6 km downstream, was analyzed and hydrographs at different cross sections were examined. The results were mapped onto topographic GIS maps to identify affected areas. Approximately 30 km downstream, the settlement area in Bhalubang was inundated with a peak discharge of 48,579.29 m3/s at this location. The research will help relevant authorities devise an emergency response strategy and implement flood mitigation measures.