Fig. 5
Sequential stages of dam failure and geomorphological changes of the breach for the three cascade dams: (a) Photographic sequence showing the failure process of Dam 1, Dam 2, and Dam 3 across five stages: Stage I (Diversion Erosion), Stage II (Headward Erosion), Stage III (Breach Development), Stage IV (Backflow Inundation, when applicable), and Stage V (Water Level Decrease). The timeline for each stage is provided in seconds. Yellow arrows indicate the progression of key processes, such as gully formation, headcut collapse, and backflow. Note that Dam 3 does not exhibit a “backflow inundation” stage due to hydrodynamic constraints; (b) Cross-sectional profiles of the breach bottom at different stages for all three dams. Initial breach configurations, breach widening, and residual profiles are marked with dashed and solid lines. Key measurements, including breach width, slope angles, and erosion depths, are labeled for each stage to illustrate geomorphological evolution. t = 0 indicates the moment when the water level in the reservoir of Dam 1 reaches the bottom of the breach.
