JWSS - Journal of Water and Soil Science

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Submerged vanes are low aspect ratio flow-training structures mounted vertically on the river bed at an angle to the prevailing flow. The aim of application of vane is to generate a secondary circulation in the main flow, designed to modify the near-bed flow pattern and thus redistribute flow and sediment transport within the channel cross section. Collar is a flat sheet with low thickness fixed vertically on the pier at stream bed level or near it. Installation of a collar leads to protect the river bed against the direct impact of downflow produced at the upstream face of the pier and therefore reduces the scour depth. This research is a laboratory study that examines the effectiveness of submerged vanes and combination of submerged vanes and collar as a pier scour protection device. Experiments were conducted in an 8 m long and 0.8 m wide flume and a cylindrical pier used was 6 cm in diameter. Clear-water scour tests with u*/u*c = 0.9 were performed with a collar 3 times wider than the pier diameter at the stream bed level and submerged vanes 1.5 times longer than the pier diameter at the stream bed level (H=0). Different arrays of vanes with different angles to main flow direction were employed. The highest reduction in the depth of scour hole with four vanes and a collar showed 61% reduction in scour depth.

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Floodwater Spreading (FS) plays an effective role in improving soil fertility, ground water recharge, vegetation cover, and desertification control. The soil fertility might increase as a result of a suitable suspended sediment material transferred to the downstream by flood events. To define a relevant FS method which increases the efficiency of the FS projects, it is necessary to study the quality and quantity of transported sediment material, spatially and temporarily. In this research, this subject was investigated by taking soil samples throughout 13 FS stations for physical and chemical analysis over 5 years. Within each of the 13 selected stations in the three first flooded dikes, soil sampling was carried out using random-systematic method. The total Nitrogen, absorbed Phosphorous and Potassium, and Organic Carbon of each sample were analyzed. Because of the abnormality of data, nonparametric test was adopted to compare means. All stations were classified into three groups using cluster analysis method. Based on the results, the variations of fertility factors are irregular between the dikes and amongst years. This could have been affected by several factors such as the quality and quantity of diverted flood, the characteristic of FS sites, and irregularity of sediment material deposited on the sites. Despite the low quality of soil fertility prior to the construction of these stations, in general, FS has a considerable role in improving the soil fertility. However, desirable objectives may be achieved in long term through occurrence of diverse flood events and suitable maintenance of the stations.

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Sediment sources fingerprinting is needed as an autonomous tool for erosion prediction, validation of soil erosion models, monitoring of sediment budget and consequently for selecting soil conservation practices and sediment control methods at the catchment scale. Apportioning of eroded-soil into multiple sources using natural tracers is an integrated approach in soil erosion and sediment studies. The objectives of this study, as a first work, are to assess spatial variations of biochemical tracers and theirs validation in discriminating sediment sources under different land uses and water erosions at catchment scale and to apply them as fingerprints to determine relative contributions of sediment sources in Zidasht catchment, Iran. In view of this, 4 enzyme activities as biochemical tracers were measured in 42 different sampling sites from four sediment sources and 14 sediment samples. The results of discriminant function analysis (DFA) provided an optimum composite of two tracers, i.e. urease and dehydrogenase that afforded more than 92% correct assignations in discriminating between the sediment sources in the study area. Sediment source fingerprinting model was used based on optimum composite of two tracers resulting from DFA to explore the contributions of sediment from the four sources. The results showed that the relative contributions from rangeland/surface erosion, crop field/surface erosion, stream bank and dry-land farming/surface erosion sources were 11.3±5.3, 8.1±3.8, 75±8.5 and 3.6±2.5, respectively. Therefore, we can conclude that fingerprinting using biochemical tracers may help develop sediment fingerprinting models and as a first step facilitate a more complete tool for fingerprinting approach in the future.

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Rivers as a main sources of supplying water for urban areas, agriculture and industry, are very important. This point reveals the necessity of the control, improvement and solving the problems of rivers, especially all problems relating to water quality. In this study, transport of the suspended sediment is numerically modeled. The Saint-Venant hydrodynamic equations and also advection-dispersion equation (ADE) are applied for modelling flow and suspended sediment transport. It is necessary to choose appropriate empirical and/or semi-empirical equation to accurately estimate the equilibrium suspended sediment discharge, as well as the appropriate equation describing longitudinal dispersion coefficient. In this research, 5 and 6 equations were applied in the ADE for estimating equilibrium suspended sediment discharge and longitudinal dispersion coefficient, respectively. 30 combinations of these equations were made and the final model was run for each of them separately. Comparison of the predicted suspended sediment concentrations and the corresponding measured values at the survey site, Abdelkhan Station, for the calibration and verification periods showed that the combination of the Van Rijn's equilibrium suspended sediment equation and the Fischer's longitudinal dispersion equation performed very well. The maximum percentages of errors in estimation of suspended sediment concentrations were 19.56% and 26.3% for the calibration and verification periods, respectively.

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The Marls are unstable sedimentary formations that contain chemical materials and destructive particles. Marls Erosion processes are very intensive, so different forms of erosion on the marls as badlands are of specific characteristics in marl lands. Hence, recognition of effective characteristics in marls erodibility is necessary to adopt corrective measures and methods. In this research, for assessing marls erodibility in Hablehroud watershed portable rain simulator was used. Runoff and sediment amounts were measured in each marl unit. Then effective Factors were identified using statistical parameters. Finally, by factor analysis we determined the relationship between marls chemical properties and sediment yield. Therefore, effective parameters of erosion and sediment yield were determined. Results showed sediment yield is decreased in gypsum marl, sandy marl, salt marl and limy marl. In addition, erosion and sediment yield are increased with increasing EC, Na, Cl, SAR and with decreasing TNV, HCO3

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Climate situation changes over a year cause changes in some soil characteristics and soil sensitivity to erosion. Investigation of these changes and how they impact on erosion can be of particular importance. This study investigated changes in Sediment Productivity and soil factors affecting these changes in Tiregan rangeland located in Daregaz city in Khorasan Razavi province. In this study, using the position of the upper and lower hillside of eastern and western aspects, the sampling with rain simulator was performed. Characteristic features of sediment yield including runoff threshold, runoff volume, sediment and turbidity were measured. Soil samples were taken from each sample rain simulation and features of the initial moisture content, bulk density, electrical conductivity, pH and organic matter were measured. Sample was collected with the same intensity and duration of the instrument with fixed locations, and was repeated in four seasons. In order to obtain the position and orientation of each of the parameters in the data obtained at different seasons, the combined analysis of variance test was used. The effect of each of these parameters and the difference between them were evaluated using the Tukey test, and the graphs in 2007 Excel software were plotted. The results showed that all the parameters of sediment yield during the year have significantly changed. The maximum amount of sediment production rates occurred in autumn and was gradually reduced. Its decreasing in both winter and spring can be attributed to vegetation in the area.

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One of the usual ways to dissipate excess energy in the dam's downstream is hydraulic jump. Hydraulic jump is a rapidly varied flow, in which the flow conditions change from supercritical to sub-critical with a large amount of energy loss. In this research, a combination of two water jets in the form of overflow dam and underflow through a slot on the body of an ogee dam with the USBR standard was established in order to decrease the length and sequent depth in a hydraulic jump. In these experiments, the underflow from the slot was designed with three out passages of 0, 45, and 90 degrees in respect horizontal line. Six different discharge ratios were used for each slot and the effect of each experiment conditions on decreasing of the length and sequent depth of hydraulic jump was investigated. The results showed that the confluence of two jets with 45 degrees from the slot had the maximum effect on the reducing of the length of hydraulic jump and sequent depth, and when 26 percent of the total discharge passed through the slot as underflow, it caused the length of hydraulic jump to be reduced by 50 percent in comparison with the classic jump. This slot not only decreases the length and sequent depth of hydraulic jump but also the sediment behind the dam can be evacuated through it. Moreover, it increases the discharge coefficient.

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The real estimation of the volume of sediments carried by rivers in water projects is very important. In fact, achieving the most important ways to calculate sediment discharge has been considered as the objective of the most research projects. Among these methods, the machine learning methods such as decision trees model (that are based on the principles of learning) can be presented. Decision tree method is a hierarchical multi step method which is a recursive data collection technique to binary and smaller sub-divisions until the final analysis cannot be divided. Decision trees consider a priori known set of data and derive a decision tree from it. Then, tree can be used as the set of laws to predict unknown features. In this research, the efficiency of this technique for predicting the suspended sediments in Ilam dam basin has been investigated. To evaluate the accuracy of the methods (written by MATLAB software), statistical criteria such as R, BIAS, RMSE, r2 and MAE were computed. The results showed that based on all the statistical criteria, decision tree in comparison with the sediment rating curve had most consistency with the observed data. Meanwhile, the most important factors for creating tree in the model (that had high correlation with sediment data) are the corresponding discharge and daily rainfall.

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The present study aimed to compare the effect of land cover on runoff and sediment with different coverage levels in Mehrian watershed. The study was carried out in a plot with the dimensions 3 × 2 meters during one year, in three different treatments (including without coverage, grass treatment and integrated treatment having brush and grass coverage) and in three replications. At the end of each plot, runoff and sediment collection tanks were installed. Sampling was performed during a year. The monthly rainfall, and runoff and sediment after harvest were determined. Then, runoff and sediment samples were transferred to the laboratory and calculated through decantation method. Also, the amount of plant cover with the plots of 60 × 25 was determined. Statistical analysis using SPSS was performed. Results indicated that the minimum and maximum runoffs in covers without plots and shrub cover and integrated cover were equal to 38 and 162, , 15 and 74, 15 and 96 liters, respectively. The minimum and maximum sediments were equal to 8.3 and 21, 8.1 and 11, 9.1 and 13 gr.l. Statistical analysis in the Spilt plot design showed significant differences between treatments in runoff and sediment (P <0.01). Also, the results showed that the amount of runoff in a bush cover is 2.1 times more than the cover without treatment, 8.1 times more than the integrated treatment, and in the integrated treatment 1.1 times more than bush cover. In contrast, the rates of sedimentation in the above treatments were 4.2, 6.1 and 5.1, respectively.

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The type and intensity of soil erosion in a region generally depend on climatic conditions, ups and downs, soil and land use. Of these, land use is most important. Using different systems of ploughing after unconscious and non-scientific change of land use affects soil physicochemical characteristics. This fact especially in marginal lands and mountainous regions is more visible. In order to investigate sensitivity to soil loss and erosion in various land uses of Aghajary deposits, part of Margha catchment with an area of 1609 hectares in Izeh city was selected. This was to determine the relationship between soil loss by rain simulator and some soil physicochemical characteristics like percentage of very fine sand, sand, clay, silt, pH, Ec, moisture, Calcium Carbonate and organic materials in different land uses. Then, sediment sampling in 7 points, three replicates and in various intensities of 0.75, 1 and 1.25 millimeters in minute in range, residential and agricultural land uses was done using rain simulator. In order to investigate effective factors in sediment production and erosion, samples of soil layers (in depth range of 0-20 cm meters) equal to the number of sediments were taken. For statistical analysis, EXCEL and SPSS 11.5 software were used. In total, the amount of runoff in residential land use was highest and in agriculture land use was lowest. The amount of sediment in agriculture land use was highest and in residential land use was lowest. Then, the most important factors in sediment yield were diagnosed by multi regression. The results showed that sediment yield and erodibility in land uses have meaningful differences in various intensities of precipitation. Regression models showed that in the production of sediment in various land uses, from among the measured factors, silt, sand very fine, lime, Ec, organic materials and pH had the greatest role. Sand percentage in the residential land use, and very fine sand and organic matter in agriculture land use had the most important role in sediment production. But in range land use, moisture percentage and pH had the biggest role in sediment production.

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  Prediction of sediment load transported by rivers is a crucial step in the management of rivers, reservoirs and hydraulic projects. In the present study, in order to predict the suspended sediment of Taleghan river by using artificial neural

network, and recognize the best ANN with the highest accuracy, 500 daily data series of flow discharge on the present day, flow discharge on the past day, flow depth and hydrograph condition (respectively with the average of 13.83 (m³/s), 15.42 (m³/s), 89.83 (cm) and -0.036) as input variables, and 500 daily data series of suspended sediment, as the output of the model were used. The data was related to the period of 1984-2005. 80 different neural networks were developed using different combinations of variables and also changing the number of hidden-layer neurons and threshold functions. The accuracy of the models was then compared by R² and RMSE. Results showed that the neural network with 3-9-1 structure and input parameters of flow discharge on the present day, flow discharge on the past day and flow depth was superior (R²= 0.97 and RMSE= 0.068) compared to the other structures. The average of the observed data of sediment and that predicted by the optimal model (related to test step) were 1122.802 and 1184.924 (tons per day), respectively.

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In many water resource projects such as dams, flood control, navigability, river aesthetics, environmental issues and the estimation of suspended load have great importance. The complexity of sediment behavior and mathematical and physical model inability in simulation of sedimentation processes have led to the development of new technologies such as fuzzy logic which has the ability to identify nonlinear relationship between input and output variables. In this study, the application of fuzzy clustering algorithm in estimating the annual amount of sediment was studied. So, the corresponding data of flow and sediment discharge of Valykben station in kasilian basin during 1349-1350 till 1353-1354 period was daily determined. The data was divided in two groups i. e. 75% as training data and 25% for test data. Then, the efficiency of model was obtained by using statistical parameters such as correlation coefficient, nash-satklyf coefficient, mean square error root and variance ratio. The result showed that the classification of data on the annual time scale and use of fuzzy clustering algorithm can estimate 0.49 values of the measured annually suspended sediment transport. Furthermore, on the same scale of classification, i.e. annual scale, this value was obtained 0.19. Thus, using fuzzy clustering algorithm can lead to higher accuracy and reliability than rating curve method, which is suggested for estimating suspended sediment transport.

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Sediment is as one of problems related to water resources utilization. Numerous formulas have been developed for bed load estimation in rivers. In this study, eleven common formulas including hydrologic and hydraulic methods such as Einstein Tofalti Meyer, Peter and Muller Van Rayne Modified Van Rayne Yalin Bagnold Fraylink Habibi and Sivakumar and Samaga were used for selection of the most suitable bed load estimator formula in Kharajgil hygrometry station on Navrud river. The results showed that Habibi and Sivkumar formula is the most suitable with the mean computed to observed data=1.35, standard deviation computed to observed=1.96, RMSE=1.63 and ill sorted ratio(computed transportation ratio to observed)=33.82% within the range of 0.5 to 2.

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Evaluation of hydrologic behaviour and soil erosion as an environmental crisis is important in order to maintain watershed ecological safety at optimum level. The aim of this study is to evaluate the performance of the distributed hydrological WetSpa model in simulating erosion and sediment transport and also sedigraph in Taleghan watershed, Iran. Base digital maps and daily meteorological time series data for 9 years are the major model inputs. The calibration of global parameters was done for the first 5 years and the model validation was carried out for 4 years considering three month warm-up period at the beginning of both calibration and validation periods. The Nash-Sutcliffe criterion for the calibration and validation periods pointed out the efficiency of model simulation (82.7% and 79%, respectively). The next phase, the erosion module was calibrated for erosion and sediment transport simulation. The results showed the Nash-Sutcliffe efficiency criterion (60% and 64% for suspended sediment concentration and transport, respectively). Overall, the evaluation results reveal the good ability of WetSpa model in simulation of the hydrological processes e.g., runoff, raindrop detachment, runoff detachment, net soil loss, etc., in a given time and space

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In this research, sediment production and delivery amount by Darabkola forest roads was estimated using the SEDMODL model. To evaluate the model results, the sedimentation rate in the above roads was directly measured using rainfall simulator. Also, the paired t-test, BIAS, RE and RMSE were used to assess the results. The analysis showed that the rate of sediment production from study roads' surface using the SEDMODL model and direct measurement under the rainfall simulation were 420.97 and 341.19 tons per year, respectively, and rate of sediment delivered to the stream with sediment delivery ratios of 42% and 51%, respectively, was about 177.58 and 174.02 tons per year. Also, results of the statistical methods of BIAS, RE and RMSE for the aforesaid model were 0.04, 17.59 and 0.71, respectively, and at 95% confidence level, no significant difference was obtained between the observed and estimated data. Therefore, the aforesaid model has the appropriate accuracy and efficiency to estimate the sedimentation rate of the Darabkola forest roads. It was also found that from among the input parameters of model, longitudinal slope of road, precipitation and sediment delivery factors were the most influential factors in the sediment production and transport, respectively.

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Cohesive sediments have large specific surfaces which enable them to absorb other cohesive sediments and polar particles such as mud and sodium. Floccules form by joining these particles. The behavior of cohesive sediments in aquatic environments is completely different from that of granular sediments. Under certain value of shear stress, the structure formed from cohesive sediments is divided into smaller particles, which can be eroded easily. Up to now, researchers have proposed empirical formulas which correlate the rate of erosion to the bed shear stress and the rheological characteristics of cohesive sediments. In this study, the calibration and verification tests are performed on Mike21 software to attain the results more adjusted with the experimental data. Afterwards, the data are developed by the model and converted to the dimensionless form. Finally, an exponential function is proposed for the erosion rate in cohesive sediments. It is found that the coefficient of determination is 0.99

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Information on suspended sediment variation in times of flood is important in management of water resources, particularly management of basins, and in investigation of the causes of erosion. The relationship between discharge and suspended sediment concentration during floods is not similar and homogeneous for different reasons such as precipitation variety, discharge rate and sources of sediment and production of hysteretic loops. In this study, the instantaneous values of suspended load were simulated using genetic programming and regression methods. By comparing the two models, Genetic programming model was selected as the better one with the mean square error and determination coefficient of 0.8 and 0.5, respectively. Then based on this model, loops of suspended hysteretic load were drawn for the six events recorded in the period of 1387-1383. This resulted in 4 linear and 2 clockwise hysteretic loops for the river suspended sediment. Identifying various hysteretic loops is effective in determination of relative contributions of processes to production and transfer of sediment including amount and intensity of precipitation, flow rate and previous moisture conditions of watershed. The results showed that the clockwise hysteretic loops occurred usually in high precipitation and discharge, and linear hysteretic loops in spring because of low intensity precipitation.

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Land use is one of the basic factors for controlling the hydrologic behavior of watersheds. Therefore, it is generally assumed that land use change is the cause of variation in hydrological dynamic of watersheds. In this paper, the land use effect in present and optimum conditions on sedimentation of watershed was studied using GIS and applying the HEC-HM model in Shoor-Shirin watershed in Fars province. Land use map was provided based on curve number map, and this map was considered as the important factor for HEC-HM model. The results showed that the estimated sediments in two different conditions were completely different. In fact, the estimated sediment in the optimum condition was 12% less than the current land use. This means that land use change and land use type play important roles in decreasing or increasing the peak flow and erosion.

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Sediment yield of watersheds results from different erosional and hydrological processes which make it too complicated to be predicted. Awareness of runoff and sediment yield regimes is useful to better understand the erosional condition of watersheds for management. Therefore, determination of factors controlling hydro-sedimentary response of watersheds is very necessary. For this purpose, ground surveying and measurements of hydrograph and sediment graph were carried out in the representative basin of Khamsan in the uplands of Gavshan dam during 9 months. Finally, relationships between runoff and sediment yield were obtained, then corresponding runoff-sediment events were analyzed. Results showed that 5 events out of 6 occurring runoff events had eight-shaped hysteresis loop and only one event showed clock-wise hysteresis loop. Among them, the highest and lowest flood discharges were attributed to the events of 02.11.2010 and 05.01.2011 with 151488 M3 and 11764.8 M3 Run off, respectively. The study also showed that for this watershed no specific type of loop existed for a particular season. Accordingly, the seasonal patterns could not be attributed to a particular type of loop. Precipitation and runoff characteristics may have also played a role in addition to other factors. Results emphasize the importance of rainfall distribution and rising-falling limbs of hydrograph for the corresponding hysteresis loops in small watersheds.

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Since the development of surface water control needs accurate access to flow behavior of sediment rates, the lack of sediment measurement stations, the novelty of most stations and the lack of statistics on the deposit make it difficult to properly evaluate and simulate the flow behavior and their sediments. In a watershed, the morphological characteristics and sediment load of flow affect each other. It is, thus, important to know about the extent of this relationship to manage and control the flow in downstream areas. In the present study, using artificial neural networks and sediment rating regression methods based on the data from 136 events and also morphological parameters, we have attempted to predict the sediment load of Bagh Abbas basin. In the first step, we used flow data to predict the sediment load of both methods, and then basin morphological characteristics such as the compactness factor and form factor were added to the models. The results of this study showed that by using neural networks of Multilayer Perceptron (MLP) type with Levenberg – Marquardt algorithm and the stimulation function of tangent Sigmoid with two hidden layers and four neurons in each layer, we can predict suspended sediment discharge rate with a sufficient accuracy. Accuracy of the results obtained from the ANN method was higher than the accuracy of rating curve method. In the evaluation of NGANN & GANN network methods and SRC & MARS regression methods, correlation coefficients were respectively calculated as 0.94, 0.93, 0.767, 0.766, and root mean square errors (RMSE), 0.45, 0.49, 2.3 and 2.3. Nash coefficient (NS) was calculated respectively as 0.71, 0.58, 0.27 and 0.23. Therefore, the most efficient method among the four models is artificial neural network combined with morphological data (GANN). Furthermore, the findings of the study show that adding geomorphological parameters to sediment rating has little effect on the model performance.