Analysis of behavior and hydraulic characteristics of flow over the dam spillway is a complicated task that takes lots of money and time in water engineering projects planning. To model those hydraulic characteristics, several methods such as physical and numerical methods can be used. Nowadays, by utilizing new methods in computational fluid dynamics (CFD) and by the development of fast computers, the numerical methods have become accessible for use in the analysis of such sophisticated flows. The CFD softwares have the capability to analyze two-and three-dimensional flow fields. In this paper, the flow pattern at the guide wall of the Kamal-Saleh dam was modeled by Flow 3D. The results show that the current geometry of the left wall causes instability in the flow pattern and making secondary and vortex flow at beginning approach channel. This shape of guide wall reduced the performance of weir to remove the peak flood discharge.

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Sediment entering lateral intakes depends on the flow pattern at the intake entrance. Using a structure in front of the intake entrance can change this pattern and as a result the entering sediment. One of the effective method to change the pattern and manage sediment entering a lateral intake is to use a skimming wall. The removal of sediments from the intake entrance using a skimming wall led to reduction of sediment volume at the intake. To guide flow into the diversion canal and increase skimming wall performance a spur dike was utilized at the opposite side of the intake channel. In this study, the effect of the skimming wall's angle with the bank, a combination of spur dike and skimming wall and discharge changes on controlling sediments entering the intake, intake ratio and bed topography were investigated experimentally. The effect of a skimming wall with three angles (10°, 14°, and 18°) and a combination of skimming wall and spur dike on opposite sides of the intake were investigated. Conducting dimensional analysis, non-dimensional ratios were extracted and test variables were specified. Results showed that in the case of having a skimming wall combined with a spur dike, the amount of sediment entering the intake decreased by 81%, 78.5% and 76% on average for walls with angles of 10°, 14° and 18° respectively. Combining a skimming wall and spur dike has a higher effect on reducing sediments entering the intake compared with a skimming wall alone by about 15%.

In this paper, the trap efficiency (TE) of retention dams was investigated using laboratory experiments. To map the relation between TE and involved parameters, artificial intelligence (AI) methods including artificial neural network (ANN), adaptive neuro fuzzy inference system (ANFIS) and support vector machine (SVM) were utilized. Results of experiments indicated that the range of TE varies between 30 and 98%; hence, this structure can be recommended to control sediment transport in watershed management plans. Experimental results showed that by increasing the longitudinal slope of streams, TE decreases. This finding was observed for Vf/Vs parameter, as well. By increasing the mean diameter grain size (D50) and specific gravity of sediments (Gs), TE increases. Results of all applied AI models demonstrated that all of them have suitable performance; however, the minimum data dispersivity was observed in SVM outcomes. It is notable that the best performance of transfer, membership and kernel functions were related to tansig, gaussmf and radial basis function (RBF) for ANN, SVM and ANFIS, respectively.

Channel junctions and lateral intakes are always caused turbulence in the passing flow. In this research, an experimental study was carried out to explore a possible method for sediment control for a series of skimming walls and a single spur dike, simultaneously. In order to direct the flow into the diversion channel and increase the skimming wall function, a single spur dike was utilized at the opposite side of the intake channel. The flow patterns for three conditions, including (1) without structures, (2) with skimming wall and (3) skimming wall and spur dike, are considered. The results showed that the use of skimming wall and a combination of skimming wall and spur dike makes it possible to direct the thalweg toward the intake port. In addition, by using the skimming wall, a trench is made toward the intake, which in turn increases the impoundment efficiency by 81% in the skimming wall combined with spur dike and up to about 66% for using the skimming wall.