Risk Analysis for Dam Overtopping Considering Hydraulic and Hydrologic Parameters (Vanak Dam as a Case Study)

Document Type : Research Article

Authors

Associate Professor, Department of Civil Engineering, Isfahan University of Technology

Abstract

In this study, a probability- based methodology is formulated to evaluate quantitatively and
systematically the overtopping risk of earth dams. This study considers the overtopping phenomena
induced by the occurrence of flood and wind effects. The risk analysis based models for overtopping
consist of random modeling of the flood generation, wind dynamic aspects, reservoir routing, reservoir
geometry, inflow discharge, outflow discharge, dam height, initial water surface and correction factor
for increasing water induced by wind. For calibrating the results of simulation and modeling, Vanak
dam in Charmahal Bakhtiari is used as a case study. The case study was employed to demonstrate how
the total risk of overtopping over a practical case could be estimated based on the proposed
methodology. Annual maximum series of peak flow discharge and wind velocity of Vanak dam are
used to analyze extreme flood and wind with different frequencies by using hydrological frequency
analysis software (HYFA). Risk analysis results show that considering uncertainties of random
parameters affects significantly the dam reliability. Also overtopping risk of Vanak dam is not
sensitive to increasing initial water surface. By increasing uncertainty of inflow flood, overtopping
risk is increased.Risk overtopping increases, while the uncertainty of reservoir geometry increased.
Also dam reliability is decreased by malfunction of spillway’s gates. Based on this analysis both the
effect of wind and flood together influence the overtopping risk of earth dam.