Local scour due to free hydraulic jump downstream hydraulic structures may cause damage or complete failure of these structures, so controlling of this phenomenon is very important. The main goal of this study is to reduce the characteristics of a scour hole downstream sudden expansion stilling basin. An experimental study was conducted to study the effect of expansion ratio and position of the sill. Ninety experimental runs were carried out considering the wide range of Froude numbers ranging from 3.42 to 8.67. Five values of the expansion ratio (e = 2.73, 1.92, 1.76, 1.50 and 1.25) and four values of the relative position of lateral single sill (Lx/LB = 0.20, 0.30, 0.40 and 0.50) were investigated. The dimensional analysis was employed to drive expressions correlating the different variables affecting the scour phenomena. It was found that, the flow patterns in most of the cases were a symmetrical and the resulting scour and deposition were also a symmetrical. The relative scour depth, the relative scour length and the relative energy loss, increase by increasing the initial Froude number and vice versa. The expansion ratio (e = 1.50) gives the minimum values of scour dimensions. The best location of the sill for reducing the scour dimensions at 0.30LB from the gate opening. Prediction equations were developed using