Risk and uncertainty analysis for dam overtopping – Case study: The Doroudzan Dam, Iran

Abstract There is a growing tendency to assess the safety levels of existing dams by using mathematical and statistical methods. In this study, the application of risk and uncertainty analysis to dam overtopping is presented for Doroudzan Reservoir located at the south part of Iran. The main objective of the overtopping analysis of dams is estimating the height of water in the reservoir under various inflows and comparing the computed results with the dam crest elevation. Hence, the main steps of this study include univariate flood frequency analysis of annual maximum inflows to estimate the peak flows in various return periods, generate inflow hydrographs based on the estimated peak flows, and route the hydrographs through the reservoir to compute the maximum height of the water in reservoir. In this study, the spillway discharge coefficient, quantile of peak flows, and initial water surface level are subject to uncertainty, and the Monte-Carlo simulation (MCS) and Latin hypercube sampling (LHS) are applied to perform the uncertainty analysis. In addition to inflows, the effect of different wind speeds on the probability of overtopping has been considered. The results demonstrated that both increasing water level and wind speed have significant impact on the risk of overflowing.