This study aims to develop a comprehensive flood routing model and calculate dam breach parameters at the Sepaku Semoi Dam, located in East Kalimantan, Indonesia. The research is driven by the increasing threat of floods due to climate change and urban expansion, emphasizing the importance of effective water management strategies. The study focuses on potential causes of dam collapse, particularly overtopping and piping, and investigates whether the Sepaku Semoi Dam has experienced overtopping through flood routing analysis. The Zhong Xing HY21 model is used to calculate breach parameters, providing insights into potential dam failure scenarios. The research methodology integrates hydrological and hydrodynamic modeling, involving field surveys, data collection, and the application of advanced hydrological techniques such as the HEC-RAS model. Sensitivity analysis is conducted to identify critical conditions that can cause dam failure, and model validation is performed by comparing simulation results with historical data. The study concludes that the Sepaku Semoi Dam did not experience overtopping during the simulation, as the remaining guard heights exceeded the standard requirement. The average collapse widths for upper, middle, and bottom piping were 57.46 m, 75.63 m, and 85.93 m, respectively, with collapse durations of 11.96 hours, 3.99 hours, and 2.39 hours. These findings enhance understanding of flood dynamics around the dam and provide valuable data for flood risk management and emergency planning.This study aims to develop a comprehensive flood routing model and calculate dam breach parameters at the Sepaku Semoi Dam, located in East Kalimantan, Indonesia. The research is driven by the increasing threat of floods due to climate change and urban expansion, emphasizing the importance of effective water management strategies. The study focuses on potential causes of dam collapse, particularly overtopping and piping, and investigates whether the Sepaku Semoi Dam has experienced overtopping through flood routing analysis. The Zhong Xing HY21 model is used to calculate breach parameters, providing insights into potential dam failure scenarios. The research methodology integrates hydrological and hydrodynamic modeling, involving field surveys, data collection, and the application of advanced hydrological techniques such as the HEC-RAS model. Sensitivity analysis is conducted to identify critical conditions that can cause dam failure, and model validation is performed by comparing simulation results with historical data. The study concludes that the Sepaku Semoi Dam did not experience overtopping during the simulation, as the remaining guard heights exceeded the standard requirement. The average collapse widths for upper, middle, and bottom piping were 57.46 m, 75.63 m, and 85.93 m, respectively, with collapse durations of 11.96 hours, 3.99 hours, and 2.39 hours. These findings enhance understanding of flood dynamics around the dam and provide valuable data for flood risk management and emergency planning.