Impact of a submerged trapezoidal broad-crested weir on local scouring at a bridge pier under clear water conditions

Abstract This study investigates the impact of a submerged trapezoidal broad-crested (TBC) weir on local scouring around a uniform single circular bridge pier under clear-water flow conditions. The TBC weir was installed downstream of the pier, and its effectiveness was evaluated based on variations in separation distance and weir height. The results indicated that the presence of the TBC weir significantly reduced the scour depth and altered the geometry of the scour hole. The impact of the TBC weir was most pronounced when the separation distance between the pier and weir was minimal. Three different weir heights were analyzed to determine the optimal configuration for scour mitigation. Additionally, this study identifies the threshold distance beyond which the influence of TBC weirs on scour mitigation becomes negligible. The findings reveal that the maximum scour reduction of 69.57% occurs when the TBC weir height-to-water depth ratio (Z/h) and separation distance (S) are 0.47 and 0, respectively, where the pier and weir are in direct alignment.