Comparative analysis and risk assessment of dam-break floods: taking Pingshuijiang Reservoir as an example

Due to the huge potential energy associated with water storage in reservoirs, dam-break floods are often catastrophically destructive for people and structures downstream. This study aims to simulate and compare floods generated under various dam-break scenarios and their downstream impacts, taking Pingshuijiang Reservoir in southeastern China as an example. A two-dimensional hydrodynamic model is used to simulate the downstream evolution of floods under three dam-break scenarios, and the breach flood and downstream inundation process are analyzed. Gradual failure of the main dam leads to near-total inundation of the nearby town over c. 1 h, allowing time for warning and evacuation. Instantaneous failure of the main dam results in larger peak flow, greater submergence depth and faster inundation (20 min), leaving little time for warning/evacuation. Instantaneous failure of the auxiliary dam generates a much lower peak flow magnitude and, although the town is still largely submerged within 45 min, the shallow water depth and low velocity are conducive to rescue/evacuation. The results show significant variation in flood process and submergence due to dam size and failure mode that provide guidance for dam-break flood risk assessment and disaster avoidance planning.