Investigating the Effect of Obstacle Installation in the Widened River Part on the Bed Load Transport Using a Laboratory Model

Sediment control is one of the issues of paramount importance in designing irrigation networks and water supply facilities. The most important methods of erosion and sedimentation management and control include basin management, sediment trap management in upstream, and sediment trap source management out of the river. Jafari et al. (2019) investigated the effect of submerged vanes and their dimensions on the bed load transport in the widened part of the river using a laboratory model. The results showed that by increasing the dimensions of submerged vanes, the speed of the bed load transport decreased, and as a result the performance of vanes improved. In a similar research strand, the present study evaluated the effect of obstacle installation and its size in the widened part of the river on the bed load transport using a laboratory model.

Using a dimensional analysis of the effective variables in the widened part of the river and installing obstacles, this study identified the influential parameters on the bed load transport. Some experiments were then carried out by simulating the widened conditions of the river in a laboratory canal. Then, a witness experiment was carried out in the widened part of the river without the presence of an obstacle. This was followed by 21 experiments in the widened parts of the river by installing an obstacle. Linear obstacle arrangement in the basin was then performed in 5 rows and 3 columns and it was considered constant for all experiments. Moreover, the discharge rate and depth, according to the initial experiments and the amount and manner of sediment movement, were constant for all experiments and equal to 10 liters per second and 0.16 meters, respectively. In order to examine the effect of the obstacle size, 15 obstacles with 0.04 meter height (hb), different width (Wb) and length (Lb) with 0/02, 0/03, 0/04 and 0.05 meters were installed and tested. At the end of the performance, the main section (i.e., the widened part) of the bed load control was examined quantitatively and qualitatively. To examine the quantitative performance of the main section, equation (1) was used. Rs = (1) In (1), Rs is the reduction in the distance of sediment flow in the widened part with an obstacle relative to the state without an obstacle (i.e., witness test), xe is the progression of sediment flow in the widened section without an obstacle, (xe- xb) is decreasing the progression of the sediment flow in the widened part with an obstacle relative to the widened conditions without an obstacle.