Resistance to flow is an important and primary parameter in the determination of water surface elevation. A variety of Bed forms, especially dunes, have a sensible effect on total roughness. Because of the complexity of Bed form development, previous methods differ drastically from each other in predicting dune Bed forms. In this paper, laboratory experiments were conducted to investigate the geometry of dunes in a sand-Bed channel and its influence on total channel resistance. The experiments were performed in a flume in the hydraulic laboratory of Shiraz University using sand particles. Simple relations were sought for dune dimensions via some dimensional parameters, and previous methods were compared to each other in light of this new data.

Friction factor plays a substantial role in hydraulic computations. In coarse-gravel Bed rivers, friction factor depends on grain size and Bed forms. A wide range of particle sizes and developing armor layer have great effects on friction factor. To this end, determination of the form friction factor of armored river Beds has been investigated in this study and, a friction equation was developed based on computing grain friction factor of the total friction factor. Analysis of obtained equation showed that the friction factor is rather independent of grain-size distribution of the Bed material and the maximum grain size of this material. The major controlling parameter is the slope of the energy grade line. These results are explained by the coupling of the friction factor with the incipient motion problem and the rearrangement of the grains of the coarsest fraction in the armor coat. To verify the equation, Keulegan method was used which results 80% agreement between two methods. Also, including the major part of total friction factor to form friction factor (40%) shows the significant effects of Bed form on flow resistance. The results of the current study showed that formation and development of armor layer increase Bed roughness and friction factor and decrease average flow velocity causing a reduction in threshold Shields parameter and augmentation in Bed stability. Field observations are employed to test the methods.

Background and Objectives: Downstream of grade control structures in watershed engineering, it is necessary to create a hydraulic jump to dissipate excess energy to prevent the destruction of the structure. A roughened Bed of stilling basins of the hydraulic jump type to increase the amount of energy loss and reduce the length of the hydraulic jump can lead to economic savings in watershed management. In this study, a new type of roughness, which is similar to the appearance of the ripple Bed in alluvial rivers, was experimentally investigate to increase the energy loss, reduce the stilling basin length and to prevent sedimentation in between the rough elements. Materials and Methods: The experiments of this research were carried out in a rectangular flume with width, height and length of 0. 3, 0. 4 and 12 meters respectively. Five different arrangements of the Bed form along with a case of no Bed form were tested under five different Froude numbers, Fr= 3. 5 to 5. 5. An Ogee weir with a height of 32 cm was installed 3 meters downstream of the flume inlet to create a hydraulic jump, and the minimum flow depth on the crest of the weir was set to be more than 3 cm to avoid the effect of surface tension. During the experiment, the water level profiles at the hydraulic jump site were measured by a point gauge with an accuracy of ±, 1 mm. During the experiment, digital photos were also taken and the required data was extracted by digitizing these photos. The average flow depth measured and extracted from the photos was used in the analysis to reduce the error. Rolling length, jump length and water surface profile were measured in each experiment and repeated three times. These lengths were also extracted from the photos and the average values were used in the analysis. Results and Conclusion: The results of the investigation of the variation of the ratio of conjugate depths versus Fr for all types of the Bed forms showed that by changing the layout of the Bed form from type 1 to type 4 of the current study, the ratio of conjugate depths (y2/y1) decreases. A maximum decrease of 10. 2% was observed for the type 4 Bed form compared to the case of no Bed form. The variation of relative energy loss (Δ, E/E1) versus Fr also showed that by changing the layout of the Bed form, the ratio of Δ, E/E1 increases, and in the type 4 Bed form, compared to the control Bed form, a maximum of 23% increase in energy loss was observed. In the investigation of the relative length of the hydraulic jump (Lj/Y2) and also the relative roller length of the jump (Lr/Y2), it was observed that by changing the Bed form from type 1 to type 4, the ratio Lj/Y2 and Lr/Y2 decreases and the maximum reduction in comparison to the case of no Bed form, was found in the type 4 Bed form, which was in the order of 32% and 34% respectively.

Hyporheic zone is related to the saturated zone beneath the river which has an important role in ecology. In this zone, part of surface water, transfer oxygen and nutrients to the organism and then returns to the surface water after certain amount of time. Hyporheic exchanges between surface flow and flow in porous media can be created due to the different Bed forms of river. Riffle-pools are topographical features found in straight, meander and braided rivers. Variation of pressure along these Bed forms lead hyporheic exchanges. The precise estimation of hyporheic exchanges and residence time can be useful for rivers restoration projects. So, in this paper, in addition to laboratory investigation of hyporheic exchanges along riffle-pool Bed forms, the variation of pressure along Bed surface has been simulated numerically by Large Eddy Simulation (LES) model and then a groundwater model and particle tracking method have been applied to simulate the flow within the hyporheic zone. The results show that the interFoam solver with LES model is able to model laboratory conditions accurately. The mean percentage error of water surface profile was 1. 8% for present laboratory study, which leads to an accurate estimation of pressure along the Bed form and as a result an accurate prediction of hyporheic exchanges. The results of hyporheic characteristics show that as Reynolds number increases, the hyporheic exchanges increase and the residence time decreases. The results also show that the residence time distribution follows generalized extreme value distribution. In this study, on average, 20 percent of surface flow exchange with sub-surface flow.

The riverBed and margin vegetation causes to increase in roughness against flow, decrease in average flow velocity, reduce water-energy, and alterations in layer velocity distribution (the flow velocity profile) across the river. In current experimental research, the effect of branching vegetation on the stream flow and Bed formation is analyzed. The flow conditions are examined in experimental channel with 7 meter length, 25 cm width and height through different flow rates (3, 5, 7 lit/s) and slopes under different(0. 001, 0. 003, 0. 005) and densities of vegetation (50, 25 and 12 percent). According to the processed data, it can be implicated that the difference between flow level, substrate, and rate is affected by the types of vegetation density; thereby existence of vegetation causes resistance to flow and depth increment. In all experiments, through the vegetation density increment, the Bed erosion increases compared with the primary condition in which the most and least alterations are observed in 50 and 12-percent density, respectively. In the condition of equal flow rate with density increment, the flow depth is increased. The Bed particle displacement in the section covered by vegetation is increased through density increment in which flow level in 50 is more than 25 and 12-percent density, as well as, flow substrate erosion and alteration whereas sediment (particles accumulation) is appeared frequently under less density at the end of section covered by vegetation.

Background and Objectives: The Bed forms or in the other word, Bed irregularities are structures that form due to stream flow and they have direct impact on roughness and flow resistance in sand Bed rivers. Bed forms have different shapes and forms in sand Bed rivers. Since river discharge and flow velocity are totally affected by roughness, accurate prediction of the shape of the Bed is of great importance. Due to the influence of different parameters in the formation of the river Bed form, it is difficult to determine the governing equations and the mathematical models with sufficient precise. Today, the use of artificial intelligence systems has expanded as a new way of analyzing water resources issues. The objective of this research is to introduce a method that can be used to predict the shape of the river Bed with high precision. Materials and Methods: In the present study, in order to obtain better results and to reduce the dispersion of data, the data were randomly divided into two parts of the training (70%) including 1647 laboratory data and test (30%) containing 560 laboratory data. The decision trees were coded on the data of the test section in the WEKA programming environment and finally calibration was performed on the data by using Random Forest and Random Tree algorithms. Then, the experimental methods of Van Rijn, Engelund and Hansen and Simons and Richardson were implemented on test data. Results: Evaluation of the results were done using root mean square error (RMSE), Correctly Classified Instances and Roc area under curve. The results showed that the best performance reached by Random Forest algorithm for experimental data with statistical criteria of CCI=85 (%), RMSE=0. 17, ROC=0. 97. On the other hand, by examining the results of empirical methods, it was determined that for laboratory data, van Rijn method has better performance with the results of CCI=64 (%), RMSE=1. 07. Among different environmental variables of discharge, width, depth, slope of the channel, average diameter of sediment particles and temperature for laboratory data were the most important parameters in predicting Bed forms. Conclusion: In this research, the superiority of soft computing models was evident compared to the empirical methods in modeling and prediction of the Bed form and the models performed in the VKA environment were better. Basically, because of the formation of the river Bed form is depended on several factors and also because of its complex nature, the prediction of this phenomenon is very difficult and sometimes with high errors. Since artificial intelligence methods are used to analyze issues that do not explicitly describe the nature of the problem, so many of the issues of Bed form can be solved with these methods.

Introduction: The industrialization of human societies is one of the factors in increasing the injection of pollution into surface waters. Contamination in the river is maintained both in the water stream and in the sediment Bed of the river. The hyporheic zone is the saturation zone of the riverBed, which has a very important function in the transmission of pollution. River Bed-form is one of the effective factors in creating hyporheic exchanges between surface flow and sediment Bed. Transient Storage Model (TSM) is one of the suitable methods in the analysis of advection and dispersion of pollution in rivers with hyporheic zone. The efficiency of the Transient Storage Model (TSM) depends on accurate estimation of the four parameters of the model (Dx, As, A and α ). Previous studies have examined the effect of Bed-form on hyporheic exchanges, but the effect of these exchanges on contamination transmission has not been considered. On the other hand, previous studies have not explored the effect of hyporheic exchanges caused by the formation of the Bed-form on the four parameters of the transient storage model (TSM). In this study, the effect of dune Bed-form on the transmission of pollution was analyzed. The effect of dune formation on the four parameters of the transient storage model (TSM) with a numerical model (OTIS and OTIS-P) and the temporal moment approach (TM) was also discussed. Methodology: Experiments of tracer material (NaCl) were performed in a flume with a length of 12 m, a width of 0. 5 m and a height of 0. 7 m applying four different flow discharges (5, 7. 5, 10 and 12. 5 l/s). The experiments were performed in the range of average flow velocity (U) from 0. 087 to 0. 361 and in the range of Froude number (Fr) from 0. 069 to 0. 290. An ultrasonic flow-meter was used to measure the flow discharge in all experiments. Grain material with an average diameter (D50) of 11. 85 mm and the porosity (n) of 0. 28 were used to create a sedimentary Bed. The first Bed (WF1) with a thickness of 32 cm, a width of 0. 5 m and a length of 10 m was created in the Flume. In order to examine the effect of sediment Bed thickness on contamination transmission, a second Bed (WF2) with a thickness of 8 cm, a width of 0. 5 m and a length of 10 m was also created. In this study, the effect of dune Bed-form on the transmission of contamination was analyzed. by creating three dune Bed-forms (D1, D2 and D3) with different wavelengths (λ ) and different amplitudes (∆ ) in the second Bed (WF2). The length of the flume was divided into three equal reaches. Two sensors were placed to measure the electrical conductivity (EC) of water in each reach aiming to monitor the concentration of contamination. A Pitot tube and an ultrasonic depth-gauge were used to measure the velocity (U) and depth (d) of water flow at each reach, respectively. The laboratory results were simulated by the OTIS-P numerical model and the four parameters of the Transient Storage Model (TSM) were estimated. OTIS-P numerical model estimates the four parameters of the Transient Storage Model (TSM) using the Nonlinear Least Squares (NLS) optimization algorithm and then simulates the breakthrough curves using the Crank-Nicolson implicit finite difference method. The parameters of the transient storage model (TSM) were estimated by optimizing the temporal moment approach (TM) relations using the Genetic Algorithm (GA) method and the breakthrough curves were reproduced using these parameters in OTIS software. Results and Discussion: The results showed that increase the thickness of the sediment Bed reduces the longitudinal dispersion coefficient (Dx). Hyporheic exchanges decrease with increasing db/d, so the amount of hyporheic exchanges in WF2 Bed is more than WF1 Bed. Increasing hyporheic exchanges in the WF2 Bed-form reduces the amount of contamination concentration in the main flow area, so the amount of longitudinal dispersion coefficient (Dx) in this Bed-form increases. The results showed that increasing Froude number (Fr) increases the longitudinal dispersion coefficient (Dx) in both cases of Bed thickness. The results showed that the storage zone exchange coefficient (α ) in WF2 Bed was higher than WF1 Bed. Decreasing db/d increases the hyporheic exchanges at the time scale (tf ∗ ), so the residence time of contamination in the sediment Bed increases. Since the storage zone exchange coefficient (α ) indicates the amount of time exchanges of contamination in hyporheic zone, so reducing the Bed thickness (db) increases this parameter. The main channel area (A) considering the D2 Bed-form case was estimated more than that in the D1 Bed-form case. Therefore, increasing the wavelength of the Bed-form (λ ) increases the share of the main flow region area (A) in the contamination transmission. On the other hand, in the case of less exchanges of contamination with the storage zone, the share of the storage zone area (As) decreases with increasing wavelength of the Bed-form (λ ). The results showed that the effect of dune Bed-form on changes in TSM parameters was in the range of Fr <0. 1. Based on the results, that the breakthrough curves simulated using both methods (TM and OTIS-P) are in good fit with the laboratory results. Conclusion: The results of using numerical models showed that increasing db/d causes decreasing the longitudinal dispersion coefficient (Dx) and decreasing the storage zone exchange coefficient (α ). The results also showed that the presence of dune Bed-form increases the main channel area (A) and the storage zone area (As). On the other hand, the presence of dune Bed-form increases hyporheic exchanges, so the amount of changes in the longitudinal dispersion coefficient (Dx) and the storage zone exchange coefficient (α ) depends on the amount of hyporheic exchanges in these conditions. The BTCs simulated by the OTIS-P numerical model and the temporal moment approach (TM) were highly agreement with the laboratory BTCs with the Nash-Sutcliffe index between 0. 89 to 0. 98 and 0. 85 to 0. 98.

Side weirs are widely used to divert water from rivers. In movable Bed rivers, deposition of sediment particles along the side weir may cause some problems in diverting water. This research is done in a laboratory flume of 0. 9 meter wide and 10 meter long with a longitudinal slope of 0. 001. Three value of weir length i. e. 0. 6, 0. 4 and 0. 2 with a single weir height of 0. 08 meter were used in the experiments. The variations of water surface profiles along the side weir were measured for various upstream Froude Numbers. The obtained results from experiments on movable Bed condition were compared with those from rigid Bed condition and also with the results from analytical solution. The results showed that Bed form made by flow regime in the vicinity of the side weir does effect on the water surface profile over the weir and thus changes the diverted flow discharge. Water surface and discharges over the side weir were found in good agreement with the results obtained from the analytical solution in compare with the results obtained from channel with movable Bed. The computed relative error for flow discharge in channels with movable and rigid Bed is 6. 35% and 24. 18% respectively. This amount for variations of water surface profiles along the side weir is 8. 03% and 9. 88% respectively.

Introduction: In alluvial streams, water flow affects the sediment and transports them to the downstream constantly. In the meantime, Bed forms will be created on stream Bed with various dimensions and in different conditions. In this paper experiments have been done to study the influences of width reduced transitions on the height of ripple forms. …