A rostral drop structure is a specialized type of vertical drop designed as a new and optimized hydraulic structure. This structure is designed to enhance energy dissipation, reduce erosion, and achieve better flow control. Considering that the natural riverbed materials are a combination of sand and clay and aiming to use bed materials that are close to the natural state of the river, clay has been used in the movable bed. The results showed that using gabion rostral drop and clay in the bed has significantly reduced scour. On the other hand, the maximum scouring depth has decreased by 40 and 16.5%, respectively, in the lowest and highest discharge compared to the case without clay. Also, the value of the relative energy dissipation parameter in the gabion rostral drop was 32.15 and 25.5%, respectively, compared to the upstream and downstream, more than the simple rostral drop. On the other hand, the comparison of simple rostral and gabion models with simple vertical drop showed that gabion and simple vertical drop models had increased the relative depth of the downstream by 67.97 and 60.46%, respectively, compared to the simple vertical drop model.
