Impact of bed sill shapes on scour protection in river bed and banks

One of the major environmental problems for river engineering, hydraulic structures and aquatic environment is the bed and bank scouring in rivers. In order to prevent this problem, six types of bed sill (including concave, convex, sine, butterfly, wing and rectilinear shapes) with 18 different configurations were examined in a laboratory flume. In this study, the scouring pattern and the depth of scouring at the downstream of the bed sill were measured. From the results, it was found that the maximum downstream scouring occurred at bank sides for concave pattern bed sill and at the centreline for convex pattern bed sill. Since the concave and convex bed sills stabilize centreline or the bank only, other types of bed sills for example sine, butterfly and wing shapes were also used in this study to stabilize simultaneously both centreline and bank of the channel. The results showed that bed sills in shapes of sine, butterfly and wing can stabilize both channel centreline and bank at the downstream of the bed sill. Among all types of bed sills, the sine shape was found to have the best performance in terms of stabilizing the centreline and bank at the downstream. Furthermore, it was observed that the location of scouring hole varies according to the shape of bed sills and the maximum and minimum scour depth were found for concave and convex shapes of bed sills, respectively.