Modeling of river phonemes is one of the main parts in Hydraulic engineering studies. Predicting the discharge in the compound open channel is the main subject of the river engineer researches. In this study the support vector machine (SVM) technique is used to predict the discharge in the compound open channel. The result of the error indexes shows that the best accuracy of the SVM by correlation coefficient 0.99 is related to the SVM model which includes the radial basis function (RBF) as kernel function. During the SVM model process obtained 0.00005 for the gamma coefficient, epsilon is equal to 0.1 and C = 1.

In this study, modeling of discharge was performed in compound open channels with non-prismatic floodplains (CCNPF) using soft computation models including multivariate adaptive regression splines (MARS) and group method of data handling (GMDH), and then their results were compared with the multilayer perceptron neural networks (MLPNN). In addition to the total discharge, the discharge separation between the floodplain and main channel was modeled and predicted. The parameters of relative roughness coefficient, the relative area of flow cross-section, relative hydraulic radius, bed slope, the relative width of water surface, relative depth, convergence or divergence angle, relative longitudinal distance as inputs, and discharge were considered as models output. The results demonstrated that the statistical indices of MARS, GMDH, and MLPNN models in the testing stage are R2 = 0.962(RMSE = 0.003), 0.930(RMSE = 0.004), and 0.933(RMSE = 0.004) respectively. Examination of statistical error indices shows that all the developed models have the appropriate accuracy to estimate the flow discharge in CCNPF. Examination of the structure of developed GMDH and MARS models demonstrated that the relative parameters: roughness, area, hydraulic radius, flow aspect ratio, depth, and angle of convergence or divergence of floodplain have the greatest impact on modeling and estimation of discharge.

Screens are one of the recent energy dissipator structures that can be used downstream of small hydraulic structures. In this study, screens were used horizontally at the brinks of the vertical drop with downstream smooth and rough bed to investigate the energy loss of the drop. Experiments were performed on two porosities of screens, a relative critical depth of 0.13–0.39 and a median size of 1.9 cm aggregates. The results showed that for a relative critical depth of more than 0.3 in a vertical drop equipped with a screen with a rough bed, the drop length with respect to smooth bed increases. Compared to applying a Type I stilling basin, a vertical drop equipped with a screen with downstream smooth and rough bed reduces the drop length by approximately 50%. Although a rough bed increases air entrainment, it has no effect on the energy loss and pool depth of a vertical drop equipped with a horizontal screen with smooth bed. The use of horizontal screens at the brinks of the vertical drop causes maximum energy loss in the downstream of drop. Equations were provided to estimate the flow parameters with a R2 value of more than 0.925 and a normalized root mean square error of less than 0.04.

The present paper aims to evaluate the effect of emergent rigid vegetation density on the flow's turbulence structure and hydraulic parameters at the non-prismatic floodplains. The experiments were performed using the physical model of the asymmetric non-prismatic compound channel. The results show that the velocity distribution in the vegetation flow is more influenced by the drag force caused by the vegetation than by the bed shear stress and does not follow the law of logarithmic velocity distribution throughout the non-prismatic section. The intense velocity gradient at the interface of the main channel and the floodplain leads to the development of strong secondary currents, increased Reynolds shear stresses, apparent shear stresses and momentum exchange in this region. Vegetation also decreases mean kinetic energy in the floodplain and increases it in the main channel. The mean turbulence exchange coefficient for the non-prismatic compound channels without vegetation was 0.23 and for the divergent and convergent compound channels was 0.035 and 0.020, respectively. The comparison of the local drag coefficient results shows that the fluctuations of this parameter are greater in the divergent section than in the convergent section due to the strong secondary currents in the interface.

In this study, a new structure named a rotary gate is introduced to control and measure the flow in canals having a semicircular or semielliptical cross section. A pivot rod, connected to the centerline of the gate and to its frame, holds the gate in place and acts as a hinge for the gate rotational movement. The gate is easy to maneuver and requires a rather small force for its movement, which makes it appropriate for network automation. The hydraulic properties of the rotary gate were investigated during an intensive experimental study and presented in this paper. Influences of the gate opening angles on the flow depths, discharge measurements, and discharge coefficients in free flow were studied using different approaches, and the results of developed relationships were evaluated. Finally, a relationship to determine the relative head loss of the gate according to the relative opening and the relative discharge was proposed.