A dam is a barrier that is constructed across the river to fulfill various purposes like agricultural activity, flood control, electricity generation, navigation, water supply, water recreation, etc. The dam protects nature and human civilization near its vicinity by becoming like a living being. Even a dam is very beneficial for our society but if it fails it creates a devastating effect. It can extensively damage entire property and losses of human life within a very short period. Its failure is very dangerous for the environment, our society, and our lives. Hence it is very important to analyze and simulate the dam failure parameters that will help to redesign, modify, and plan an emergency response for the engineers. The dam breach failure is caused by overtopping due to excessive inflow by heavy precipitation in any form, seepage, or pipping through the dam and due to mass movement landslides. Overtopping breaches develop very fast but seepage breaches take a long time to develop. The time is very crucial between initiation, detection, prevention, and flood warning. The prediction of seepage is more difficult even if it is detected, it is not possible to fully stop. In this paper, an attempt has to made to study the dam break analysis of Kosi Barrage using a 1D hydraulic model known as Hydraulic Engineering Centres River Analysis (HEC-RAS). The River Geometry data and inundation map are extracted from the RAS mapper with the help of the project file and digital elevation model. In this study breach parameters, velocity distribution, depth variation, and conveyance area of flow are considered. For overtopping and pipping failure scenarios the unsteady flow conditions were simulated by the dam break model. The probable maximum flood (PMF) corresponds to a failure condition, and at crucial downstream locations, the HEC-RAS software is used to determine the outflow condition after breaching. The results after the simulation of the breach parameter with the help HEC-RAS model and the outcomes were compared to a case study of the Hidkal dam situated in Karnataka. A sensitivity study is also done to see how the breach parameters affect peak flow and maximum stage. The area near the dam and villages is impacted by the water that results from the dam breaking. This demonstrates that failure caused by overtopping is more severe than failure caused by pipping.