Sedimentation efficiency of small dams in channels (Case study: Kermanshah province)

Small sediment dams are the key structures for controlling sediment flow and improving the course of waterways in watersheds. In Kermanshah province, the efficiency of these structures in sediment accumulation has been less studied and evaluated. This study aimed to investigate the efficiency of these structures in sediment retention and flood control in three watersheds of the province. For this purpose, while selecting three study basins in the East (Hajiabad basin), North (Razin basin), and South of the province (Mereg basin), the target dams for the study were identified. A total of 30, 14, and four dams were gabion, dry-stone wall, cement-masonry, respectively. Then, the accumulated sediments in the tank behind the dams were examined with the help of surveying and sampling from different sections. Examination of the results in the Hajiabad basin in the East of the province, which was the main cause of erosion showed that gabion and dry-stone wall construction have been able to reduce soil erosion and sedimentation by 13%. In the Razin watershed in the North of the province, cement-masonry and gabion dams had managed to trap about 886 tons of sediment. In the Mereg watershed, the results showed that the upstream dams with 9245 kg/ha had the highest and the downstream dams with 3575 kg/ha had the lowest sediment control performance. The results of this study showed that in basins with high sedimentation capacity, dry-stone wall dams are one of the most important low-cost structures to prevent sediment transport, especially coarse particles. However, the construction of dams with low drainage to prevent the transfer of fine particles is also effective.