in this study, scour of mashkid bridge pier located in mashkid river of saravan county has been studied and to measure the scour rate, the numerical model hec-ras 4.0 has been used. upon selection of mashkid river as the case study and whereas the studied zone is important with respect to the climatic conditions and showery monsoon raining and flowing the great and destructive floodwaters, therefore scour is considered as one of the most important topics in water and hydraulic engineering so that the most destructions are made following occurrence of this phenomenon. under the effect of scour process in the mode, the scour rate in the bridge piers have been estimated for a discharge with 100-year return period and different methods available in hec-ras model for estimation of scour depth. the results extracted from analytical model indicate this point that scour depth made in the piers is more than scour depth in the abutments. upon comparison of scour depth as per colorado state university (csu) equation, it was concluded that the scour in the piers was higher whilst upon applying froehlich equation, the scour depth in the abutments is increased. as well as, making a series of barriers in the cross sections of bridge upstream with the specified height and width increases or decreases the scour depth. the results provided in this study indicate that the specified height of the barriers causes the scour depth reduction. upon providing one barrier at the first section of bridge upstream, no change was made in the scour depth and the obtained results were almost similar to the initial results obtained from modeling by csu. but by providing 3 barriers of approximate height of 1.5m and cross section width of bridge upstream, it was observed that the scour depth has been reduced. summary of this modeling indicates that the scour caused by contraction has been reduced. another time, the project was modeled by providing a barrier in the immediate bridge upstream section (bridge section), and the results indicated that the scour depth has been reduced another time.