The probabilistic assessment of overtopping reliability on Akyayik dam

Abstract

Turkish Ministry of Forestry and Water Works has recently performed privatization of rivers in order to generate electricity. Akyayik dam, the first of the five intended cascading hydropower dams in Tunceli, is ready to be constructed within a short time. In this study, probabilistic assessment of overtopping reliability of Akyayik earth-fill dam is presented. Monte Carlo simulation (MCS) with combination of Latin Hypercube (LH) technique is applied. Risk and uncertainty methods have been used on safety assessments of hydraulic structures for some future years, in some of which the univariate flood frequency is employed, which is not a highly accurate technique and cannot reflect true probabilities of occurrences. The others used bivariate flood frequency analysis with limited pairs of peak discharge and the corresponding volumes for a certain reoccurrence interval as 100 years. This study is the combination of both. In the analysis, the inflow hydrographs are generated by randomly drawing peak discharge and volume values from a bivariate normal flood frequency distribution function at each iteration. In addition, initial reservoir level and wind wave setup are considered as other random variables that could induce overtopping. The maximum height of the water was calculated by employing reservoir routing that incorporates wind setup and initial reservoir level in the discrete form of continuity equation. The effects of spillway discharge coefficient and height of the dam on overtopping probability are also investigated.