One of the ways to analyze the phenomenon of scour is the numerical study of this phenomenon. Conventional software programs used in this field do not have the ability to model the rock mass. Therefore in this study the effect of rock mass strength parameters on the still basin behind the dam was analyzed. For this purpose FLOW-3D software program was used to perform fluid calculations. Then the appropriate output of this software was extracted and the rest of analyses were performed in UDEC separate elements. The results indicate the powerful influence of these parameters on the shape and form of scouring in BeheshtAbad dam. So the increased amount of cohesion and internal friction angle of the joints reduce the width and depth of critical scour and its extent. However their impact on reducing the width and depth of critical scour and its extent is not the same. Then equations were proposed to predict the depth and width of the scour. Finally, in order to reduce the phenomenon of scour grouting the rock joints was proposed and its performance was evaluated. It was observed that grouting the joints increased the amount of adhesion and reduced the internal friction angle but given the higher impact of adhesion, scour in the grouted joints was reduced significantly.