Dams are indispensable infrastructures, offering critical water management services, including storage, supply, and flood control. Despite their advantages, the failure of these structures can result in catastrophic flooding with severe consequences. This necessitates comprehensive analysis and modeling to evaluate potential dam break scenarios, predict flood impacts, and identify high-risk regions. This study conducts a comprehensive breach analysis of the Osmansagar Dam using the two-dimensional Hydraulic Engineering Centre River Analysis System (HEC-RAS) model to assess potential dam break scenarios and their impacts on downstream regions. The Cartosat-1 Digital Elevation Model (DEM) is utilized to extract river geometry and generate inundation maps, identifying areas at risk of flooding. The research focuses on predicting breach parameters, breach flood hydrographs, peak flow estimates, flood arrival times, and developing inundation maps. The dam break model is simulated under unsteady flow conditions corresponding to a Probable Maximum Flood (PMF) scenario, emphasizing overtopping failure. Breach parameters are estimated using Froehlich method to enable comparative analysis, while dynamic flood wave routing traces the flood progression. Results indicate that the immediate downstream region experiences peak flow rates of 1,73,216.92 m3/s due to the overtopping failure scenario, with the resulting flood projected to affect approximately 42,112 families across an area of 115.76 km2. The findings of this study will assist relevant authorities in planning sustainable flood mitigation strategies and developing an effective emergency response plan to minimize the potential loss of life and property in the event of a dam failure.