Many developed countries have emphasized the security and safety of their dams. Failure of infrastructure on the densely populated land would potentially result in loss of many human lives and property damages. If structural safety is ever in doubt, the dam cannot guarantee the lives of those who live at the downstream. Therefore, examination and maintenance of dam safety must be a priority. Methods for computing risk and reliability have been established for a long time. The return period method has been used for decades, although this method only considers flood frequency. Despite its simplified assumptions of uncertainties, the return period method is still widely used in practice for evaluating the risk of hydraulic infrastructures. 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. The load combination model which is used for the effects of flood and wind to gather is based on Iran committee on large dams’ recommendations. In this approach two combinations including a flood with the return period of 1000 years and a wind with the return period of 100 years, and a flood with the return period of 10000 years and a wind with the return period of 10 years are employed. Also, the maximum probable flood was considered. Two risk computation techniques; namely, Monte Carlo Simulation method and Latin Hypercube Sampling method are used and are compared. 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.