This study develops a comprehensive flood routing model and determines dam breach parameters at the Sepaku Semoi Dam, addressing the increasing threat of floods due to climate change and urban expansion. The dam serves as a flood reduction and water supply facility, and the research aims to assess whether it has experienced overtopping or not, and to calculate breach parameters using the Zhong Xing HY21 model. The study integrates hydrological and hydrodynamic modeling to enhance understanding of flood dynamics and improve flood hazard predictions. It also emphasizes the need for improved flood risk management and dam failure analysis. The research focuses on potential causes of dam collapse, particularly overtopping and piping. Flood routing analysis indicates that the Sepaku Semoi Dam has not experienced overtopping, as the remaining guard height exceeds the standard guard height. Breach parameters reveal critical insights into potential dam failure scenarios. The study also calculates fracture parameters for different piping scenarios, including upper, middle, and bottom piping, which are used in the Zhong Xing HY21 model. The results show that the dam did not collapse due to overtopping, as evidenced by the remaining guard height exceeding 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 provide insights into the potential collapse process of the dam under certain conditions. The study contributes to a deeper understanding of the factors contributing to dam collapse and reinforces the structural integrity of the Sepaku Semoi Dam in facing extreme flood loads. Although the dam did not collapse due to overtopping during the simulation, detailed understanding of collapse parameters is important for future planning and risk mitigation. The research highlights the importance of integrating flood modeling and dam breach parameter calculation for effective disaster risk management.This study develops a comprehensive flood routing model and determines dam breach parameters at the Sepaku Semoi Dam, addressing the increasing threat of floods due to climate change and urban expansion. The dam serves as a flood reduction and water supply facility, and the research aims to assess whether it has experienced overtopping or not, and to calculate breach parameters using the Zhong Xing HY21 model. The study integrates hydrological and hydrodynamic modeling to enhance understanding of flood dynamics and improve flood hazard predictions. It also emphasizes the need for improved flood risk management and dam failure analysis. The research focuses on potential causes of dam collapse, particularly overtopping and piping. Flood routing analysis indicates that the Sepaku Semoi Dam has not experienced overtopping, as the remaining guard height exceeds the standard guard height. Breach parameters reveal critical insights into potential dam failure scenarios. The study also calculates fracture parameters for different piping scenarios, including upper, middle, and bottom piping, which are used in the Zhong Xing HY21 model. The results show that the dam did not collapse due to overtopping, as evidenced by the remaining guard height exceeding 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 provide insights into the potential collapse process of the dam under certain conditions. The study contributes to a deeper understanding of the factors contributing to dam collapse and reinforces the structural integrity of the Sepaku Semoi Dam in facing extreme flood loads. Although the dam did not collapse due to overtopping during the simulation, detailed understanding of collapse parameters is important for future planning and risk mitigation. The research highlights the importance of integrating flood modeling and dam breach parameter calculation for effective disaster risk management.