Earth dams under certain conditions are constructed as arch shaped in plane. This may have different reasons such as foundation problem, stability of the body of the earth dam and seepage. Change in the earth dam shape results in its discharge changes too. This is one of the reasons why this study was made. The main purpose of this study is to examine the numerical analysis for verifying the extent of discharge and hydraulic gradient variations of arch dams. For this purpose, a series of numerical analysis by FLAC 3D software were made, and the impact of parameters such as the shape of the valley, height of the dam and the radius of the arc were examined. The results showed that as the radius of the arc increases, discharge rate of the dam in both types of the valleies decreases. In a valley with a constant cross section at a certain height, discharge rate is more than a narrow valley. The results also showed that discharge and arc length have linear relationship. The analysis also showed that, average of hydraulic gradient downstream of arch dams is greater than the straight dams.