The risk of earth fills during heavy rains is evaluated in this research. The rainfall intensity and the variability of the numerous soil parameters of the earth-fills related to soil erosion are dealt with as probabilistic parameters. When the peak overflow head on a spillway bed becomes greater than the design overflow head, overflow occurs. The peak overflow head, is determined within 72 hours of the rainfall, and the various rainfall patterns are tested by the Monte Carlo method. Furthermore, the statistical values of the parameters for the soil erosion are assumed, and the variability of the discharge hydrographs are derived from the values. The discharge hydrographs are applied for the flood simulation as input waves. The submerged area and the head of the flood discharge in the downstream area can be predicted. Considering disaster loss, the risk to the downstream area of the earth-fill dams can be evaluated.