The study of dam breach analysis helps predict the flow in case of dam breaches and helps in disaster preparedness. By using the Hydrologic Engineering Center’s River Analysis System (HEC-RAS), an overtopping failure scenario of the Krishnarajasagara dam in the Cauvery River in Karnataka has been simulated. Flood wave propagation is simulated till the Mettur Dam, located about 212 km downstream, in the Salem District in Tamil Nadu. Two-dimensional flow simulation using HEC-RAS is used to estimate the plausible inundation extent and flood wave arrival time at various points downstream of the dam. Probable maximum precipitation for the area is used to compute the flood inflow to the dam at the time of breach. The peak flow is estimated at 25,000 m3/s. The simulation results show a time interval of 49 h between the breach of the Krishnarajasagara Dam and the flood wave arrival at the Mettur Dam reservoir.