جستجوی مقالات مرتبط با کلیدواژه « sedimentation » در نشریات گروه « آب و خاک »

One of the natural structures in rivers is mid-channel bar that is created due to shear stress decreasing and sediment deposition in the central part of river. Bifurcation and erosion are seen in rivers because of mid-channel bar existence. Also, energy loss is the other impact of mid bars that would intensify the deposition in rivers. Mid-channel bar is known as one of the most important aquatic habitats, so there is necessity to find more information on flow structures around it in operation processes and river restoration. In this research, the flow structures around mid-channel bars are assessed as laboratory study. Three mid-channel bars were made in the shape of rhombic, ellipse and lemniscate in this research. These shapes are common in natural alluvial rivers. This study was established in a laboratory flume by length of 9 meter, and width and height of 0.4 meter. The bed slope was fixed of 0.0007. This flume was located in the water and sediment research laboratory in Gorgan University of agricultural sciences and natural resources. Three-dimensional velocity of flow was collected using an electromagnetic current velocity sensor with a frequency of 30 Hz in 39 data points. The flow discharge was fixed as 4.5 liter per seconds using a frequency flow meter. The flow regime was subcritical and turbulent in all examinations. Findings showed that bar shapes have different impacts on flow structures and amounts of energy losses. Comparison between plots implied that there are similar conditions in elliptical and lemniscate shapes but a little different in rhombic case. The variation range of transverse velocity was between 0.4 to 1.6 times of average value for all shapes. According to the results, the existence of elliptical bar led to significant tolerance in longitudinal velocity in all axes (between 0.5 to 1.6 times the average in left and right axes and 0.2 to 1.4 times the average value in central line), but these tolerances were not significant for lemniscate and rhombic bars (between 0.8 to 1.2 times the average value in left and right axes and between 0.8 to 1.4 times the average value for central axis). The variation of vertical velocity in middle axis presented the maximum decrease before facing elliptical bar and similar conditions for this axis in facing with lemniscate bar, except that this decrease is started exactly at facing point here. In addition to the values of the velocity components, the direct effect of encountering bars should also be sought on the values of the flow energy as a cumulative indicator of the erosive power of the flow. A more detailed analysis of the graphs shows left that in the and right axes, encountering the elliptical bar has led to an increase in the relative energy of the current by 1.4 times the average, and after passing through the bar, the energy load has decreased to less than the average value. But in the middle axis, the presence of the bar reduced the relative energy of the flow to 0.6 average value and after passing through the bar, this component has an increasing trend. Exposure to the elliptical bar led to the greatest changes in the relative values of the triple velocity components, compared to the rhombic and lemniscate bars. Also, the changes in the total energy load caused by the presence of two rhombic and lemniscate bars are insignificant, but similar to the changes in all three velocity components, transverse, longitudinal, and vertical, the elliptical bar led to significant changes in the relative values of the total energy load along the channel.

Rivers are always faced with erosion and sediment transport. Sediment transport in rivers is one of the most complex topics in river engineering and is always the focus of experts and water engineers. This phenomenon is one of the important hydrodynamic processes that affect many hydraulic systems and water facilities and is considered one of the basic problems in the exploiting surface water resources globally. Estimating the sediment load of rivers is one of the important and practical issues in the studies and design of water engineering projects, such as the design and development of irrigation and drainage networks, water extraction from rivers, etc. Sediment concentration can be calculated by direct or indirect methods, which are usually expensive and time-consuming direct methods. Various factors affect this phenomenon, which makes their analysis difficult. Therefore, they cannot model the sedimentation phenomenon with acceptable accuracy. Hydraulic models cannot always be trusted due to the need for a lot of data, unavailability of the required data, and the inaccuracy of the data due to human error for simulating sediments. Nowadays, fuzzy and neural intelligent conductor systems, due to their ability to solve complex and nonlinear phenomena, have found many applications in various water engineering problems, including sedimentation. The purpose of this research is to evaluate and compare adaptive neural fuzzy models (ANFIS), support vector machine (SVM), gene expression programming (GEP), and group model of data handling (GMDH) in estimating the sediment load of Tirah River, Markazi Province.

In this research, first, the long-term daily statistics of temperature, rainfall, average flow rate, and sediment concentration of Hasan Abad hydrometric and sediment measuring station located on the main branch of the Tirah River were collected. Then, the data sufficiency test for analysis, checking the correlation between parameters of river discharge, precipitation, temperature with sediment discharge, and determining the long-term average of suspended sediment in the studied stations were performed. In the next step, a suitable combination of input variables was selected. The design of the input parameter pattern can be based on the relationship between flow and sediment flow parameters, rainfall, temperature, flow, and sediment flow. Of course, considering that the mentioned parameters have a historical course, therefore, the design of the input patterns of soft computing models should be done based on time delays (like what is discussed in the analysis and forecasting of time series). Determining the most appropriate time delay of the input parameters in the modeling of discharge, sediment, temperature, and rainfall, then the appropriate design of the structure of the used soft calculation models was done. In the next step, the estimation of sediment discharge using an SVM, GEP, and ANFIS group method of GMDH data control and comparison of three data mining methods, and also with the sediment rating curve and observational data. About 70 % of the research data was used as training and between 20 to 30 % for validation and testing.

Based on the statistical indicators of optimal model selection, the best performance of the SVR model has been obtained for model number one. In this model, the R2 and RMSE obtained from the model are 0.96 and 0.0047, respectively. Besides, the R2 and the RMSE error of the models in predicting suspended sediment values in the test stage are 0.95 and 0.014, respectively for the ANFIS model, and 0.50 and 4.97, respectively for the GEP model. The best performance of the ANFIS model has been obtained for model number one. In this model, the R2 and the RMSE obtained from the model are 0.95 and 0.014. The R2 and RMSE of the models in predicting suspended sediment values in the test stage are 0.96, 0.0047 for the SVR model, and 0.50, 4.97 for the GEP model, respectively. The best performance of the GEP model has been obtained for pattern number nine. In this model, the R2 and RMSE obtained from the model are 0.99 and 0.010, respectively. The R2 and the RMSE of the models in predicting the amount of suspended sediment in the test stage are respectively equal to 0.70, 0.015 for the ANFIS model and 0.78, 0.0185 tons respectively for the SVR model.

It can be seen that the performance of the GEP model was better compared to other models. SVR and ANFIS models are ranked second and third. In the next step, the best-selected pattern of ANFIS, SVM, and GEP models was used as the input of the GMDH model. First, input pattern one, which was selected as the best pattern for ANFIS and SVM models, was introduced as the input of the GMDH model. In the training and test, the values of R2 statistical indices are 0.94 and 0.99, respectively, the RMSE error value is 0.0079 and 0.0038, respectively, the MSE value is 0.000062 and 0.000015, respectively, and the MAPE values are respectively 0.007 and 0.003. In the next step, input pattern nine, which was selected as the best pattern for the GEP model, is introduced as GMDH input. In the training and test steps, the value of R2 is equal to 0.95 and 0.98 respectively, the RMSE error value is equal to 0.0077 and 0.0045 respectively, and the MSE value is equal to 0.0006 and 0.00002 respectively, and MAPE value is equal to 363 and 502. The results showed the acceptable performance of the GMDH model with the highest R2 equal to 0.99 and 0.98 and the lowest RMSE equal to 0.0038 and 0.0045, respectively.

In most regions of Iran, the requisite water for population and industry is supplied by groundwater resources. Drought is an important factor, which affects groundwater quality. Groundwater is a renewable, limited, and vital resource for human life, social, and economic development. It is a valuable part of the ecosystem and is vulnerable to natural and human effects. Recognizing the quality of underground water, as one of the most important and vulnerable sources of water supply, has been a matter of course in recent decades. The effects of corrosiveness and sedimentation in water supply systems, water transmission, and distribution can increase operating costs and also create negative effects on human health. Therefore, the science of water quality will remain an important issue for engineers and scientists for years to come. Many methods and techniques have been invented and developed to investigate the chemical quality of water. Excessive harvests and recent meteorological droughts have changed the quality of underground water, but so far no study has been conducted in the entire Sefid-Rud Basin area to investigate the quality and the process of its changes. Therefore, the purpose of this study is to investigate the chemical quality of Sefid-Rud water which is used for the industry.

In this research, the chemical quality of underground water sources in the Sefid-Rud Basin has been studied and analyzed using the results of the qualitative analysis of water samples in deep wells, semi-deep wells, springs, and aqueducts, separately for three periods and according to the common statistical period of 18 years (2001-2018). The analyzed statistics and information include the results of a complete chemical analysis of water and parameters such as electrical conductivity (EC) values, total dissolved substances (TDS), pH, cations (Ca, Mg, Na, and K), anions (Cl, SO4, HCO3, and CO3), Na, and sodium absorption ratio (SAR) have been investigated. Water used by industries depending on the type of consumption in different sectors should also have certain qualities and characteristics. In this research, the Langiler index, which is an index for Corrosion and Scaling, was used to classify water quality for industrial purposes. To this end, the chemical quality of water in terms of chemical balance and occurrence of corrosion and scaling phenomena of underground water was classified into three categories: sedimentation, balanced, and corrosive. The Langelier index was used to measure water quality for the industry.

In the statistical analysis of groundwater in the Sefid-Rud Basin, while determining the maximum, minimum, and average values of qualitative parameters at the level of the study areas, the trend of qualitative changes at the level of their aquifers according to the EC map of the groundwater, has been analyzed. In the whole period of 18-year statistics (2001-2018) in the Goltapeh-Zarinabad and Tarom-Khalkhal areas, the average values of EC and TDS are higher than in other areas. there has been an increasing trend in the Goltapeh-Zarinabad area during the three study periods. Among the cations, the calcium ion had the highest amount (except for Goltapeh-Zarinabad and Tarom-Khalkhal areas), followed by the sodium ion. The highest amount of Na ion was observed in the area of Tarom-Khalkhal, the highest amount of Ca ion was observed in the Divandareh-Bijar, and the highest amount of Mg ion was observed in the Taleghan-Alamot. HCO3 and then SO4 ions were the main anions in the entire statistical period and all the study areas. It followed a relatively constant trend in all the study periods. According to the qualitative classification of industrial water, about 67% of the samples have corrosive properties and about 32% are depositors.

The values of EC and TDS in the three statistical periods in the area of Goltapeh-Zarinabad had an increasing trend. The sodium absorption ratio (SAR) in the entire statistical period was 2.9% with a maximum in the Tarom-Khalkhal range and a minimum of 0.8% in the Manjil and Sojas ranges. It shows the maximum values of cations for Ca ions with 3.6 in the Divandareh-Bijar range, Na with a value of 5.8 in the Tarom-Khalkhal range, and Mg with a value of 3.8 in the Goltapeh-Zarinabad range. Besides, the maximum amounts of anions including HCO3, SO4, and Cl were in Astane-Kuchesfehan, Divandareh-Bijar, and Tarom-Khalkhal areas, respectively. Qualitative assessment of groundwater resources in the Sefid-Rud Basin area for industrial use based on the Langiller index shows that the changing trend of this index has been relatively stable in the three periods, and out of 360 sources in the basin, 241 are corrosive sources, 115 are sedimentary sources and four sources have had a balanced situation. The analysis of qualitative zoning maps for industrial purposes showed that the Astana-Kuchsefahan and Divandre-Bijar aquifers, the central part of the Zanjan aquifer, and the western areas of the Goltape-Zarinanabad aquifer have sedimentation characteristics and other aquifers have corrosive characteristics.

Erosion and sedimentation in river arches cause problems in river structures. Therefore, the pattern of flow and transport of sediments in the open channels of meandering River has attracted the attention of river engineers. Since the flow field in the bends of rivers is three-dimensional, therefore, in the last few decades, the prediction of changes in bed level and changes in the location of banks with the help of computer programs has been given more attention.In this study, using SSIIM software, topographical changes of meandering channels with sinus generator and moving bed have been modeled, and bed level changes have been studied under different conditions. For this purpose, solid beaches Natural rivers are principal resources of water and energy. Design and operational management of natural rivers needs a complete knowledgement of mechanics of flow pattern and sediment transport. The complex three-dimensional flow characteristics inriver bends reveals the necessity of using a three-dimensional numerical model.The numerical model used in the present study is called SSIIM, an acronym for Sediment Simulation in Intakes with Multi block option. In this study, in the first step, SSIIM is applied to investigate the characteristics of turbulent flow in a Sine-Generated channel with 70-degree angle, the rectangular cross section of width B =40cm and fixed bed. In addition, a comparision has been also made between the turbulence models, the flow characteristics such as Longitudinal and transverse velocity, Water level and bed Shear stress has been considered. The results have been validated with laboratory data. The results show that SST-k-ω model has better consistency with experimental data than k-ε model. Also distribution of bed shear stress depends on Froude number although secondary flow is independent. Furthermore, distribution of bed shear stress and secondary flow is dependent on the width to depth ratio. For b/h<8, another circulation cell occurs near the outer bank.In the second step, to investigate the variation of channel bed subjected to steady flow, Channel with movable bed has been employed. Comparison of results show good agreement between computed and measured bed topography. Finally, the effective parameters including interval time step, grid size, Froude number, width to depth ratio and meandering angle has been investigated. Results show that by increasing the Froude number and the ratio of width to depth point bar and point pool gradually migrate downstream channel. Whereas by increasing meandering angle, point bar and point pool moving Upstream.

Scouring at the place of submerged pipelines under the effect of eddy currents around the pipe passing through the riverbed leads to the settlement and failure of the pipeline as well as the penetration of the fluid passing through the pipe into the stream. Therefore, efforts to reduce these risks and their effects are always the attention of researchers and engineers. In the current research, scouring and sedimentation around the pipe and its surrounding bed under the effect of a protective plate at different positions and heights have been investigated and analyzed using Flow-3D. A comparison of the simulation results of the present research with the laboratory results showed that the used numerical model with the statistical index R2=0.96 has an acceptable ability in simulating the mentioned phenomenon. Also, the results showed that by installing a plate with a height of H=1.25D (D is the diameter of the pipe) and at a distance of 0.5D downstream of the pipe, the scouring depth under the pipe decreases by 60%, and also the average level of the bed in the upstream area increases by 82%, which is the most optimal state among different downstream positions. The optimal state of the plate in the upstream corresponds to the height of H=0.75D and at a distance of 1.5D, which not create scouring, and the average level of the bed between the pipe and the plate in the upstream has increased 4.9 times compared to the state without the plate.

Intake canals of off-stream reservoirs, play a key role in achieving reservoir goals. Chahnimeh reservoirs have been constructed to store and use water optimally for drinking, agricultural development and play a complementary role to flood control. The Sistan plain in the southeast of Iran is highly dependent on surface water resources. The HEC RAS model is a well-known one-dimensional software for flow and sediment simulation. In this study, HEC RAS 6.0.0 was used to simulate sedimentation in feeder 2 canal under maximum conditions as well as minimum water level conditions of Chahnimeh reservoirs. Flow simulation in the model was performed quasi-unsteady using the standard step-by-step method by a flood hydrograph with a volume of one billion cubic meters. According to the simulation results, in maximum water level Conditions, Feeder 2 canal Sedimentation volume is equal to 54,200 m^3 which increases the bed level by 4.1m. Also, in minimum water level Conditions, sedimentation is equal to 52,700 m^3, which increases the bed level by 3.84 m. Comparison of the results in the two scenarios shows that in the case of maximum water level, volume of sediment per unit of length of Sistan River is equal to 6.5 m^3⁄L_River while in minimum water level volume of erosion is equal to 2.2m^3⁄L_River of Sistan River. Although feeder 2 canal in minimum water level conditions increases the inflow from the Hirmand river due to the decrease in the river bed level of sistan river but will act as a sedimentation canal in all conditions.

Considering that Iran is a country where most of its locations have arid and semi-arid climates and with a scarcity of water preventing losses of this national resource is extremely important. One of the ways to prevent losses is to implement basic and scientific irrigation networks and increase the efficiency of water transfer. Therefore, it is necessary to evaluate the work done on irrigation networks and determine them as weak and strong. In this study, to estimate the water transfer efficiency of irrigation and drainage network of Ramshir left coast, 5path channels type canalet of B-block were selected as samples. Among the canals studied, some of them had water overflow problems in the body due to sedimentation in the bed and others didn't have this problem. The amount of discharge for each section was calculated according to the operating conditions in winter and negligible evaporation and by obtaining the difference in discharge in the entrance and output of each section from the sample channels, the water transfer efficiency was determined. The results of this study showed that the water transfer efficiency in the canals without overflow problems was between 88.40% and 89.18% and in the channels with water overflow problems from the body was between 63.66% and 71.52%. The reason for the reduction of water transfer efficiency in the channels with  overflow problems is due to the sedimentity of the water supply (Jarrahi River), their inappropriate slope and its consequences is the reduction of the power of sediments transport in the canal bed by the flow of water.Therefore, the effect of decreasing the flow transfer capacity due to the change in roughness coefficient due to sedimentation in the canal bed and also occupying part of the flow channel by sediment and water flow in parts of the body of these canals has reduced the water transfer efficiency and increased the losses. In order to improve this condition and improve the water transfer efficiency in the mentioned network, It was suggested that sediments with diameters greater than 1 mm in water supply and before transferring to canals by trapping sediment pond and sedimentary particles up to 1 mm that enter the studied canals should be transferred using the change slope of the current status of the canal and prevent sedimentation in their bed

Density current is one of the factors influencing the transfer of sediments to reservoirs of dams. One of the practical methods to control sediments is to build an obstacle in the path of these currents.

In this laboratory research, the behavior of the Density current under the effect of cylindrical obstacles made of wood with a diameter of 1.5 cm and a height of 30 cm (more than the height of the body of the Density current) was evaluated. Therefore, by considering variables such as floor slope, concentration and discharge, the values of the density current head were determined. Machine learning algorithms such as adaptive neural fuzzy inference system and artificial neural network were used to model the results.

Based on the results, the density salt flow head was modeled using machine learning algorithms such as adaptive fuzzy neural inference system and artificial neural network and the performance of these two methods were compared. The results showed that machine learning algorithms are useful in modeling the density salt flow head. And the regression of the adaptive neural fuzzy inference system for the training and test data was 0.99 and the regression of the artificial neural network was 0.94 and 0.91, respectively.

By comparing the two methods, it was found that the adaptive neural-fuzzy inference system is more effective in modeling the percent reduction of the head of Density current than the feed-forward artificial neural network method.

One common method for Blank River protection and restoration is use of Spur dikes. Spur dikes either in the forms of group or single, depending on their permeability is classified an permeable and impermeable. Spur dikes restore flow pattern and prevent erosion of river banks. This leads to stability and immovability of river. However, they have some disadvantages; on installation they require drying river and erosion around their structure causes destruction (Anonymous, 2002, 2003) and (Anonymous, 2010). Due to the mentioned disadvantages use of spur dikes will be halted and use of vane, which has a higher environmental compatibility, is suggested. This study aims to introduce “composite structure”; a new structure with a combination of a Spur dike with different permeability and a single vane. The main aim of this study is to increase the amount of sediment transported behind the structure by water flow produced by the vane in the combination structure.

Due to the importance of the topic in the fluid transfer industry, the way of pipelines across the width and bed of the rivers has been considered especially in recent decades. In practice, the passage of pipelines through meandering rivers and river bends is unavoidable. In this research, local scouring of buried and semi-buried pipe in 90-degree mild bend under different scenarios was investigated. The results of this research can help the functioning of rivers and their interaction with structures in the river such as buried and semi-buried pipelines, predicting the amount of water washing around them and using its results in the design and placement of these pipelines.

The laboratory model on which the scenarios of this research are based includes an arc-shaped channel located in the hydraulic laboratory and physical models of the water science and engineering department of Razi University. In this arc-shaped flume, the length of the upstream span is 5.4 meters, the length of the downstream span is 4.5 meters, the inner radius is 1.6 meters, the outer radius is 2.1 meters, the height is 0.6 meters, and the floor width is 0.5 meters. In order to check the correct functioning of the physical model and to trust its results, an experiment was conducted without the presence of the pipe buried in the bend. In this experiment, the flow descent number equal to 0.32 and sediments with a uniform grain and a diameter of 0.85 mm and a thickness of 15 cm were placed in the flume bed. After conducting the test for 6 hours and not observing the movement of the bed load, the pump was finally turned off and after the complete drainage of the flume, the bed profile was measured.

The effect of the placement angle of the repeller pipe relative to the mild arc (θ) on the scouring pattern
The results showed that by placing the pipe in the repulsive state, the amount of scour after the pipe and under the pipe has increased compared to the attracting state. According to the placement angles, it was observed that in repulsive mode, with the increase of the placement angle of the pipe in the bend, the amount of scouring after and under the pipe has increased. The effect of the placement angle of the attracting pipe relative to the mild arc (θ) on the scouring pattern In the absorbant state, it was observed that by approaching the beginning of the arc and reducing the placement angle of the pipe due to the non-alignment of the flow direction with the pipe direction, the amount of scour after the pipe decreased, but the process of scouring under the pipe was observed as in the repulsive state.The effect of pipe placement depth on scouring pattern By increasing the depth of pipe placement, it was observed that the effect of the pipe on local erosion has decreased; Even in some simulation scenarios, the placement of the pipe in the depths with the ratio of the placement height to width of the channel of 0.06 buried pipe has no effect on the local erosion. It can be concluded that at depths equal to or greater than The ratio of placement depth to channel width is 0.06, the effect of local scouring caused by the buried and semi-buried pipe is minimal, and as a result, it causes the least damages.

The results showed that by placing the pipe in the repulsive state, the amount of scour after the pipe and under the pipe has increased compared to the attracting state. According to the placement angles, it was observed that in repulsive mode, with the increase of the placement angle of the pipe in the arch, the amount of scouring after and under the pipe has increased. However, in the absorbiant state, it was observed that by approaching the beginning of the arc and reducing the placement angle of the pipe due to the non-alignment of the flow direction with the direction of the pipe, the amount of scouring after the pipe decreased, but the process of scouring under the pipe was observed as in the repulsive state.

Estimating the sediment load of rivers is one of the important and practical issues in the studies and design of water engineering projects, such as the design and development of irrigation and drainage networks, water extraction from rivers, etc. Sediment concentration can be calculated by direct or indirect methods, which are usually expensive and time-consuming direct methods. Various factors affect this phenomenon, which makes their analysis difficult. Statistical and regression models are the most common methods of analysis, which often provide erroneous results due to the linear solution of these phenomena. Therefore, they cannot model the sedimentation phenomenon with acceptable accuracy. Hydraulic models cannot always be trusted due to the need for a lot of data and sometimes the unavailability of the required data and the inaccuracy of the data due to human error for simulating sediments. Nowadays, intelligent fuzzy and neural conductor systems, due to their ability to solve complex and nonlinear phenomena, have found many applications in various water engineering problems, including sedimentation. The purpose of this research is to evaluate and compare adaptive neural fuzzy models (ANFIS), machine Support vector (SVM) and GEP gene expression programming in estimating the sediment load of selected rivers in Central Province. For this purpose, the performance of three types of support vector machine (SVM), adaptive neural system (ANFIS) and GEP gene expression programming in the simulation of sediment load of rivers was studied.

In this research, first, the long-term daily statistics of temperature, rainfall, average flow rate and sediment concentration of Hasan Abad hydrometric and sediment measuring station located on the main branch of the Tirah River were collected. Then, data sufficiency test for analysis, checking the correlation between parameters of river discharge, precipitation, temperature with sediment discharge, and determining the long-term average of suspended sediment in the studied stations were performed. In the next step, a suitable combination of input variables was selected. The design of input parameter pattern can be based on the relationship between flow and sediment flow parameters, rainfall, temperature, flow flow and sediment flow. Determining the most appropriate time delay of input parameters in flow and sediment modeling. Estimation of sediment discharge using support vector machine (Svm), gene expression programming (GEP) and fuzzy-adaptive neural system (Anfis), comparing three data mining methods with each other as well as with gauge curve and observational data. The appropriate design of the structure of soft calculation models is used, in this research the number of data required for training (usually more than 70 percent), research data as training and also determining the required data (usually between 20 and 30 percent) is used for validation and testing.

In this research, The best performance of the GEP model has been obtained for pattern number 13. In this model, the R2 explanatory coefficient and the RMSE error obtained from the model are 0.97 and 0.033, respectively. The coefficient of explanation R2 and the RMSE error of the models in predicting suspended sediment values in the test phase were obtained as 0.53, 3.18 for the ANFIS model, and 0.70, 15.16 for the SVR model, respectively. Comparing the results of ANFIS and GEP models with the SVR model indicates the superiority of the GEP model in predicting the amount of suspended sediment according to Verdi model number 13. According to the obtained results, it can be seen that the performance of GEP model was better compared to other models. SVR and ANFIS models are ranked second and third. According to the obtained results, it can be said that the GEP model as a powerful and high-speed model can be used to model the suspended sediment in the Qomroud catchment area of Bagherabad station.

The results show the acceptable performance of the models compared to the gauge curve. Also, the results showed the superiority of the GEP model with the highest coefficient of determination R2 with a value of 0.99 and the lowest root mean square error RMSE in terms of tons per day with a value of 0.010. In this regard, the efficiency of the SVR model was somewhat better than the ANFIS model. The obtained results showed that all three investigated data mining methods provide far better results than the sediment gauge curve.

Due to scouring problems in impermeable spur dikes, which compromise structural strength and stability and as a result repair and maintenance costs increase, an alternative method of scouring is needed to protect the river bank. In this area, bandal-like structure can be used. This structure is a combination of an impermeable spur dike and a permeable spur dike. The upper part is impermeable causes the upper half of the flow run towards the center and the inner wall and the lower part is permeable enabling the lower half of the stream passes through it (Rahman et al., 2003a, b). The lower part causes the flow to slow down and reduces speed, and because the flow near the bed has a higher concentration, it leads to settling sediments in the downstream of the river near the coast. On the other hand, because of the flow through the lower half, the power of downstream flows are reduced compared to the impermeable spur dike and the horseshoe vortices are vanished. Therefore, the scouring rate in the bandal-like structure is less than the impermeable spur dike (Zhang et al., 2010; Teraguchi et al., 2011b)Regarding that the scouring rate, the bandal-like structure is less than an impermeable spur dike therefore, its use has been suggested by some researchers. Since the sedimentation rate behind the bandal-like structure is less than the impermeable spur dike, in the present study, a new structure called the wedge bandal-like is proposed to enhance the sedimentation of the bandal-like. Wedge bandal-like structure is constructed of a bandal-like structure and a repellent impermeable triangular spur dike. The purpose of using this structure is to use both the advantages of the bandal-like structure as well as the benefits of repellent impermeable triangular spur dike, for deviation of flow and sediment transport to the back of the structure and sedimentation. Both structures cause the secondary flow of the surface to move towards the outer arc before moving to the outer shore down the bottom and practically shore the coastal tail into middle areas.

One of the new methods for controlling erosion on the outer bank of river curve is the use of plates connected to the riverbank. Coastal vanes are the environmental structures which are used to control bank erosion, divert flow from bank to river center, improve sediment transport status, develop river for sailing, restorate and develop river's aquatic habitat. Despite the many advantages of coastal vanes, there is no detailed information about erosion and sedimentation and flow patterns around them under different hydraulic and geometric conditions and fewer research have been done. In the present study, the effect of different installation scenarios of triangular permeable vanes on bed sediment longitudinal and transverse profile changes in a laboratory channel with a 180-degree bend is evaluated.

In this research, the main purpose is to investigate sedimentation and erosion patterns in the rivers’ bend using coastal triangular vanes; in this regard, the impact of distance between triangular vanes, their effective length, and Froud number on the erosion control of the outer bank of the 180 degree bend is focused. Experiments in a laboratory flume with a mild 180-degree bend with a  ratio and a rectangular cross section with a width of 0.6 meters is done. The angle of fixed triangular vanes is 60 degrees, the height of the permeable triangular vanes from the sediment surface is 10cm and the permeability of the triangular vanes is 12%. The experiments were carried out with limpid water mode. The effective lengths of the prepared vanes were 12, 15 and 20 cm with installation intervals of 60, 75 and 100 cm respectively and were run at two different inlet discharges.

Investigating the effect of the distance between permeable triangular vanes on bed topography shows that in each Froud number, with increasing the distance of vanes from each other, the maximum scour depth will be increased. The results demonstrate the use of permeable triangular vanes causes the flow deviation from the outer bank to the center and then the inner bank of the flume, which leads to control the erosion in the river outer bank. By increasing the inlet flow discharge and increasing the effective length of triangular vanes and the distance of triangular vanes from each other in a 180-degree bend, the maximum scour depth and volume are increased. The installation of triangular vanes with an effective length of  and a distance of 5L causes the flow deviation from the outer bank to the vanes cape and the middle of the flume, consequently results in a decrease in the shear stress in the middle of the flume and scour depth of the erosion channel and creates thalweg in the vanes cape.

The results illustrate that by installing the triangular vanes, the point-bars are created in the interval between them. Therefore, during the effective length of 12cm, the maximum height of the point-bar on the outer bank equals to 30 and 31% of water depth, between the 0 to 170 degrees and 68.7 to 115 degrees equal to 11 times and 3 times the distance between the vanes, for discharge values of 13.5 and 15.5 l/sec, respectively. Also, for the mentioned conditions the width of the point-bar on the outer bank reaches  85% and 75% of vanes’ effective length , respectively. Permeable triangular vanes with six pillars are recommended for meandering rivers like  Karun in 90 and 180-degree arcs. These rivers have high torsion and curvature as well as high flow depth and low flow velocity in them, which contain high suspended sediments and the slope of this type of rivers is 0.001 or less and due to the low slope, their sediment carrying potential. Sediment loads are mostly fine.

Density current is one of the most important factors in the sedimentation process of dams. Increased sediment will reduce dam storage capacity and makes significant challenges for relevant engineers. Therefore, understanding the dynamics of density fluids and related sediment patterns is very efficient for dam reservoir management.

The purpose of this study was to create an intelligent model with appropriate adaptation to laboratory data so that, it can be used in future designs with different variables. Therefore, in this study, the percentage of reduction of density salt current head under the influence of trapezoidal permeable obstacles (aggregates with a diameter of 1 cm), taking into account variables such as discharge, slope, concentration and height of obstacles in laboratory.

Based on the results, the density salt current head was modeled using the artificial neural network feed-forward method and the classical multivariate regression method, and the performance of these two methods was compared. The results showed that the intelligent feed neural network intelligent method in modeling the percentage reduction of density salt current head is significantly superior to the multivariate regression method so that the training, calibration and test regression values ​​ are 0.99, 0.98 and 0.98 were obtained for neural network and 0.92, 0.91 and 0.91 for multivariate regression, respectively.

The performance of the artificial neural network is much better than the multivariate regression method.

Investigating and understanding river change issues is one of the important factors in sediment hydraulic sciences and river engineering. These studies can be done with the help of physical, mathematical models, or both, but due to financial and time constraints, mathematical models are more general and often used. In this study, the GSTARS model was used to investigate erosion and sedimentation and select the most appropriate function in 12.5 km in length from the Talar river in Mazandaran Province. Simulation using the 55 sections taken in 2006, the daily flow data of the hydrometric station of the Shirgah, located at the beginning of the rich and characteristics of the river sediment, was done. The calibration and validation of the model with cross sections taken in 2012 showed that Yang's sediment transport equation has the highest correlation with reality and can be used to predict river change. The amount of sediment depleted from the case study using the Yang equation is estimated at 8590 tons per year. Also, the study of longitudinal profiles of the river with different sediment transfer functions showed that the study reach at the end range has an erosion trend and is not capable of sand and gravel mining.

Due to the high cost of construction of the dams, increasing the lifespan of this construction structure has been considered by water engineers. Sediments near the dam wall reduce the useful life of this structure. Constructing obstacles in the path of density currents be is one of the most widely used methods in controlling these sediments. In this study, the effect of permeable obstacles on density current head flux has been studied experimentally. The obstacles were made in the shape of trapezoid and were filled with sand particles with a diameter of one centimeter also salt were used to prepare the density current. In these experiments, the effect of inlet flow, flume slope and obstacle height on density current was investigated. Examining the variables of this study, it has been found that the reduction percentage of the density current head flux for the dimensionless ratio of height 1 is between 33.1 to 61%, for the dimensionless ratio of height 1.5 is between 43.2 to 63.3% and for the dimensionless ratio of height 2 is between 68.2 to It is 100%, also increasing the inlet flow ratio and flume slope increases the momentum of the current and thus reduces the efficiency of the obstacles. In addition, at the end, the density current head was modeled as linear and nonlinear regression.

One of the most important and essential parts in the set of water transfer structures is settling basin in water transfer networks. Settling basins are among the essential structures that are constructed to separate sediments along the inflow, after the reservoir and at the beginning of water transfer canals. Since the presence of excess sediments is especially harmful for agriculture and aquaculture and reduces the efficiency of related productivity, the importance of these structures increases.

In the present study, the effect of placing a wall perpendicular to the flow path in the settling basin on the sediment trapping efficiency, in both walled and plain modes (without wall or control), was investigated. For this purpose, 5 physical models of sediment basins in simple (without wall or control) and walled, with height ratios of 1/3 and 1/2 to the height of the sediment basin, and with three and five walls of the compressed plastic material were made. Experiments were conducted by entering sediment particles with diameter less than 0.1mm and constant mass of 2.8kg into the rectangular concrete canal in the hydraulics laboratory of Sari Agricultural Sciences and Natural Resources University. After ending of each experiment on models the deposited sediments were collected, dried and finally weighed. In these experiments, the number and height of walls placed in the settling basin changed and their effect on the efficiency of trapping was investigated. At the end, the results of the experiments were verified using a numerical model using FLUENT software and a statistical test using SPSS software.

Experimental results showed that the presence of walls in the flow path in the settling basin significantly increased the sediment trapping rate. Increasing the number of walls from three to five, in the ratios of heights 1/3 and 1/2 to the settling basin wall, causes an increase of 5.9 and 7.65 percent on sediment trapping efficiency, respectively. The results of this study also showed that the simultaneous effect of both height parameters and the number of walls caused a 10 to 27% increase in sediment trapping efficiency. Statistical results showed a significant difference between the presence and absence of a wall on the efficiency of trapping. The results of numerical simulation also show the effect of the presence of walls on changing the flow pattern and show that increasing the number of walls has increased the amount of sediment in the settling basin.

In general, it can be concluded that the use of the wall in the passage of the stream containing sediment from the settling basin, reduces the turbulence of the inlet flow and reduces the flow velocity in the basin. It can be stated that increasing the length of the flow path and spreading the incoming sediments across the pond increases the amount of settling and trapping efficiency.

Stability of hydraulic structures is one of the main problem that usually researchers focused on it. Bed change around the hydraulic structures caused by flow is one of this effected items on stability. In this research, the scouring and sedimentation downstream of gate with different angles (30, 45, 60 and 75 degrees) has been investigated with Flow-3D software. This simulation results illustrated that Flow-3D software in addition to the prediction of scour depth and sedimentation high with R2=0.9, have acceptable results of bed shape change in simulation. The erodible bed changes showed that with increasing of angle up to 45 degrees, scour depth will increase up to 3.4 times of flow jet thickness, while for gate with 60 degrees this amount is minimum and equal to 2.8. Distance of scour and sedimentation maximum depth and high for 60 degrees was about 12 times of flow jet thickness, also wide and length of composed vortex downstream of gate were about equal to flow depth and 16 to 17 times of flow jet thickness, respectively. The vortex circulation between separation stream layer and gate, and its velocity is 10 percent of jet velocity which rotate counter clockwise. So gate with angle of 60 degrees according to scour depth and sedimentation high was the best angle for design.

Climate change is one of the most important factors influencing the hydrological cycle.The present study investigate the impact of climate change on runoff and sedimentation of the Dehbar watershed for the next 30 years using statistical model, LARS-WG and conceptual hydrological model, SWAT and WEPP. First, LARS-WG model was calibrated to generate future meteorological data in the basin. Then, the HadGEM2 model with three scenarios; RCP8.5, RCP4.5 and RCP2.6 were used to downscale meteorological data for period of 2020 to 2050. The results indicate a decrease in rainfall and an increase in temperature on the horizon of 2050. Also, the results of SWAT model show the runoff variations for RCP8.5, RCP4.5 and RCP2.6 scenarios which are -22.16%, -17.93% and -17.34%, respectively, and for sedimentation variations which are -4.4%, +9.4% and +3.2%, respectively, relative to the base period. In the WEPP model by choosing the hillslop method and using downscaled results of RCP8.5, RCP4.5 and RCP2.6 scenarios, sediment variations were estimated -6.4%, +12.6%, and +4.8%, respectively, compared to the base period.