Local scour downstream control structures may cause sevier damage or complete failure to the control structures. Through this research, an experimental study was conducted using semi-circular sill. The suggested shape is easy to be used as an extra element to existing structures to minimize the scour downstream control structures. A hundred eighty nine experimental runs were carried out considering various heights and positions of sill with different flow conditions. A case of flat floor without sill was included as original case and to be compared with the cases using sill.  The influence of using the semi-circular sill on the scour hole dimensions was evaluated. Obtained results were analyzed and graphically presented.