Reservoir’s geometry impact of three dimensions on peak discharge of dam-failure flash flood

Once a dam fails, large amount of water at rest in the reservoir burst into downstream river and can causing extensive inundation areas, damage to properties, and loss of lives. The outflow hydrograph influences from variety of factors; e.g. dam’s properties, failure mode, and reservoir specification. This paper aims to analyze the effect of two latter factors on the peak outflow discharge focusing on the relative size of the failed part employing failure ratio (a/A0) and shape of the reservoir employing shape factor (Sf) and cross section index (λ). Doing so, instantaneous experimental dam break and historical gradual failure were considered and separate analyses were carried out. Results showed that a higher peakdischarge is expected when Sf decreases or a/A0 and λ increase. Based on the experimental and historical dam failure data two distinct regression equations were developed and verified for peakdischarge estimation. The sensitivity analysis demonstrated that peak discharge is highly sensitive to the changes of the failure ratio and shape factor; moreover, it is in uenced by the cross-section index to some extent.