In various parts of the Amudarya river, transverse dams are built for channel control and to protect riverbank from scouring. Studies were carried out in CAIRI laboratory to study the hydraulics of flow near structures (dams) on both sides of the channel, specifically spreading patterns of flow overtopping and its erosive capacity. Experiments carried out on 20m x 2m erodible model for discharge values Q = 10.0, 20.0, 30.0 l/sec, contraction degree of n = B/(B-b 0 ) = 0.33, 0.5, 0.67 and with the installation angle with respect to the streambank α = 60°, 90°, 120° gave specific results. Based on theoretical and experimental studies, relationships were obtained, which allow establishing the boundaries for flow division, velocity distribution along the width and length of flow, vortex length, distances between structures, as well as the values for backflow velocities along the streambanks, that can be used to construct velocity field in the dam impact zone. The obtained methods allow to get the full picture of a flow spreading beyond dams at the presence of backflow.

In the article, based on the results of field measurements and calculations, recommendations are given for determining the roughness coefficient of the channel of the spillway. Based on the analysis of the literature and field research data, it was recommended to take the roughness coefficient of the channel of the spillway (canal) equal to n = 0.02 - for areas with steep slopes and without sediment deposits, and in areas with the worst condition of concrete surfaces and sediment deposits, take n = 0.0225. According to the results of field surveys of the canal, it was found that the hydraulic regime at the turning section No. 2 in the plan is characterized by an uneven distribution of depths in its cross-sections. This is due to the curvilinearity of the turning section of the channel, which has an unacceptably small radius of curvature in the plan causing centrifugal forces and rising levels along the concave wall, which led to an overflow of water over the top of the channel walls. As a result of the conducted experimental - laboratory studies of the turning section of the outflow tract (channel), recommendations are given for reducing the water incursion on the banks, the height of the walls.