Sensitivity Analysis of Rock-Fill Dam Break Flood on Different Dam Break Durations

The dam break pattern of rock-fill dams is normally gradual failure. This kind of dam failure is caused by seepage piping or overtopping, in which dam crest overflow is more common. The dam breach expansion process shall depend comprehensively on the structure pattern, material property of dam, and damsite cross sectional topography. And the break duration has a significant impact on the magnitude of break flood and the counter-measures for excess-standard flood. Take the Karot Hydropower Project constructed on the Jhelum River in Pakistan as an example, the dam break mathematical model is set up to analyze the sensitivity of damsite discharge process, downstream highest flood water surface profile and flood peak appearance time to dam break duration. The results show that: with the increase of dam break duration, damsite peak discharge is decreased sharply, flood peak appearance time extends, on-way highest water levels below Karot dam are lowered significantly, and some settlement places below Karot dam can avoid being inundated until the break duration reaches a critical value. If encountering probable maximum flood, the dam break occurs when the reservoir water level reaches dam top EL, some measures can be taken to extend the break duration, so as to effectively reduce the loss of downstream flood. The research results will help to understand the relationship mechanism between rock-fill dam break flood and break duration and provide a scientific basis or some solutions for optimization design of dam and counter-measures of dam break flood.