Scour downstream irrigation and hydraulic structures is very dangerous because it can easily causes complete or at least partial failure of these structures if they are not designed to take to impact of scour into consideration. Sudden expanding stilling basins are used widely in irrigation canal systems downstream of weirs, regulators and barrages. Therefore, it is very important to predict the scour characteristics in these basins to enable a safe, efficient and economic design of sudden expanding stilling basins. Different techniques are used including dimensional analysis, experimental...