دکتر سید احمد حسینی

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.

Surface runoff and water flow in rivers cause soil erosion and carry sediment materials. Knowledge of how erosion and the ability to carry sediment in rivers and waterways should be considered in every engineering plan. One of the most important factors in disrupting the hydraulic balance of the river is the indiscriminate removal of sediments from the river bed. Today, the materials obtained from rivers are very vital in human life, especially in civil and industrial activities, and are of great importance. Indiscriminate and out-of-capacity harvesting of sand causes changes in the morphology of rivers, which results in the river's reaction to establish a new balance. The study of past research indicates that sand harvesting has caused different changes in the hydraulic pattern of rivers, changes in morphology, and changes in the sediment balance of rivers. The extraction of sand from the country's river beds has increased in recent years. Due to the complexity of hydraulic and sediment problems in rivers, it is not possible to solve the equations analytically, hence numerical methods are usually used. Various studies have been conducted using the HEC-RAS model to investigate the flow of hydraulics in the river. Various researchers in the country have also used this model to investigate sediment transfer in rivers and reservoirs of dams.

In this research, a part of the Khara River located in Khandab City, which is subject to excessive sand harvesting, was investigated. In this study, HEC-RAS 5.3 model was used to simulate sediment flow. For Joshirvan hydrometric station, discharge was calculated with a return period of 2, 5, 25, 50, and 100 years and used for hydraulic simulation of the river. To use the HEC-RAS model for hydraulic simulation of flow and sediment, river information including geometric data, hydraulic data, and sediment data was used. In the geometric section, the general plan of the river along with cross sections was introduced to the model. Using the topographical map of the river course in two time periods before sand and sand harvesting (2015) and after sand and sand harvesting (2017), a digital elevation model of the Kurkhane river course with a scale of 1:2000 was prepared for both periods. Then, a TIN was made from the prepared digital elevation model, and 200 sections were extracted in the HEC-GeoRAS add-on package in the Arc Map software along the length of 3.5 km of the river. After preparing cross-sections and measuring the distances of the left and right banks of the main channel of the river, the relevant information was connected to the HEC-RAS model in the form of a GIS file to introduce the geometry of the river. Finally, the changes made in the geometry and morphology of the river were compared by examining the parameters before and after harvesting the materials and field investigations in the periods when this operation was carried out.

By comparing the longitudinal profile of the bed in the post-harvest conditions compared to the pre-harvest conditions, it was found that in the first half of the studied interval from the upstream side (section 1-98) a sedimentation phenomenon occurred with a shallow depth, while in the middle half of the studied interval study (section 100-150) there has been an uplift of the river bottom. The results showed that the amount of erosion and sedimentation in the first 1.5 km and the last 1 km is almost low, and the materials in this area are not very removable. The best area for collecting materials in this interval from 1.5 to 2.5 km is almost in the middle of the interval. According to the changes in the river bed, the maximum change is about 1.2 meters and the average changes are about 0.5 meters along the river path.

Results showed that the rate of erosion and sedimentation in the first 1.5 km and the last 1 km almost decreased in the sedimentation state and the materials in this area are not very harvestable. The best area for harvesting materials in this range is from 1.5 to 2.5 km approximately in the middle of the range. Due to the slope and cross-sectional shape, the flow velocity has decreased and sedimentation with an average depth of 1.2 meters has been done. Calculations showed that the amount of sediment that can be removed from the river in this period is about 200 tons per year.

Sediment dams are built with multi-purpose goals including flood control, erosion, sedimentation and aquifer feeding. These dams, with the aim of controlling the sediment from transferring part of it to the reservoirs of the dams in the downstream, and by causing a delay in the surface runoff, they control a part of the flood and feed the aquifer of the area. Improper design or lack of optimal implementation of these structures causes the reduction of useful life and sometimes premature destruction of these structures. Evaluating the function and technical performance of such plans with the aim of improving and managing the system is of special importance. For this reason, in this article, a number of sediment dams implemented in Abdanan City of Ilam Province were investigated and evaluated. This research was conducted in the form of hydraulic simulation and comparison of the current situation with the conditions before the implementation of the project, in a section of the waterway about seven kilometers long. It should be mentioned that six stone and mortar dams have been built during the last decade. The results of the hydraulic simulation of the flooding of waterways and constructed structures showed that, based on the discharge with a return period of 100 years, the average overflow width of the construction dams is about 25% larger than the required value and the length of the stilling basin is about 40% less than the required value. In general, in all construction dams, the length of the stilling pond is not chosen correctly, so that the short length of the stilling pond has caused the hydraulic jump to leave the pond or to form at its end. Due to the high flow speed in the area of the hydraulic jump, erosion and destruction in the end zone of the calm pond has intensified, which has been extended to the upstream side and the main structure of the sediment dam. Based on the hydraulic simulation of the flood and the relative comparison of the results in the conditions before and after the construction of the dams, it was found that the constructed dams have a positive effect on the parameters of flow speed, flow strength and flow shear stress, which are all factors that aggravate erosion in the waterway. So that for discharge with a return period of 25 years, the speed, power and shear stress parameters of the flow have decreased by 23, 29 and 27%, respectively, during the research period. Therefore, the average reduction of these parameters locally and at the construction site of the six dams was estimated as 73, 85 and 82%, respectively. In general, according to the field visits and investigations, the implementation of the plan has been effective in controlling floods and sediments, and in case of annual protection and repair, its effects will be doubled.

Mechanical properties of most soils alter upon the increase of moisture and saturation. In some soils, certain phenomena appear due to increased moisture. Some of these phenomena lead to major damage in development projects. These soils are called Sensitive soils to water”. The most significant types of these soils are swelled soils, dispersive soils, and collapsible soils. Dispersive soils refer to clay soils that are easily washed up in waters with a low concentration of salt. Dispersion is a progressive phenomenon that starts from one point and is gradually extended. The start point of the dispersive phenomenon may refer to cracks resulting from shrinkage, soil deposition, or cracks made due to the roots of plants. This phenomenon is of great importance in such plans as soil dams and water supply channels where there is a water concentration inside the soil too. One of the essential reasons for soil erosion and sediment production in irrigation and drainage networks is the instability of canal soil, so it is necessary to use erosion control methods in parts of the canal route, especially at the intersection with other structures. To this end, the solution investigated and tested in this article is the use of biological mulches to reduce the erosion of the side slopes of earthen channels.

This research has been conducted on soil with a Loam sandy texture of irrigation and drainage channels network of the Arayez Plain of Khuzestan that lies on the west side of the Karkheh River. Using a simulated system, two-nozzle rainfall of the K18 feature was performed. To determine the effect of mulches on parameters of side wall erosive resistance of the soil structure, after the soil of the region passes through a sieve of 4.76 mm was put in the basin designed for 1 x 0.33 x 0.1 m for about 25 kg. After filtration, leveling, and pressing the soil to the edge of the Flume basin proportionate to the physical special weight of the soil, the stabilizing materials, and different bio mulches were sprayed in their different concentrations. Then, the basins inside the Flume with a side slope of 80% were put into a depth of 10 cm. In this research, with the objectives of determining the type and most appropriate level of biological mulches and their effect on the soil erosion resistance parameters of the lateral wall of the drainage channels of the Araiz plain of Khuzestan, the necessary experiments were conducted in the rain simulator laboratory of the Soil Conservation and Watershed Research Institute. So that using four types of water-based biological mulch, which were named with numbers 1 to 4 and at three levels of minimum (C1), medium (C2), and maximum (C3), experiments were conducted on the soil sample of the researched area. Each of the experimental treatments on a flume with a side slope of 1 to 1.25, similar to the side slope of canals in nature, was repeated and simulated three times in two rainfall intensities of 30 and 80 mm h-1. In each experiment, primary and secondary soil moisture, runoff volume, sediment weight, the intensity of water penetration in the treatments, and the shear strength of the treatments were measured. The experiments were conducted in a randomized complete block design in the form of split plots and the data were analyzed using SAS software and the averages were compared using the Student–Newman–Keuls (SNK) multi-domain test. Finally, by using mathematical models with optimization and minimization of sediment amounts and economic costs, the most suitable treatment for stabilizing the lateral walls of drains was determined. SPSS software was used for the statistical analysis of data and ANOVA and the Duncan test were used for the statistical comparison of data. Considering the tables obtained from data variance analysis and considering the statistic F and significance level, it can be said that all treatments are different in a significance level of 5% concerning the extent of sediment and there is a significant difference in the sediment amount.

The tests conducted on the soil of drainage channels of Arayez plain with a loamy – sand texture indicated that the presence of mulch coverage results in reduced sediment arising from rainfall in the manner that by the increase of density in any of the mulches, sedimentation reduces accordingly. The results obtained from the statistical analysis of this research confirmed that there is a significant difference in a level of 5% between sediment amounts of test control and mulch treatments for the sample of the soil under study. Therefore, bio mulches have an effective role in erosion control and the decrease of sediment from the walls of soil channels. The results indicated that only two types of biological mulches used in this study had a positive effect on shear resistance. General Linear Model (GLM) results showed that the interaction of two parameters of rainfall intensity with the type of treatment on shear strength is significant, so the interaction of rainfall intensity parameters with the level of materials used was not significant at the 5% level. In addition, the interaction of the type of treatment with the level of the materials used was also significant. According to the results of the analysis of variance in investigating the role of rainfall intensity on biological mulch treatments, it was found that rainfall intensity affected shear strength.

According to the above photos, all mulches compared to the control treatment have had a remarkable effect on the decrease of sediment. Moreover, it was found that the increase in the density of mulches used in all densities has had a remarkable effect on the decrease of outlet sediment. Furthermore, it was realized that the rainfall factor affects the increase of sediment. Thus, this effect in mulch 2 is the least effective in such a manner that upon increased rainfall in mulch 2m we see the minimum increase in the amount of sediment. The results after conducting system engineering and analyses related to the optimization of sediment amounts and economic costs indicated that mulch 2 at the C3 level has the best efficiency in increasing shear resistance. This conclusion could help the decision makers to allocate their soil conservation budget for the best performance activities.

Due to river dynamic nature, the morphological characteristics of rivers are always changing and these changes can have negative effects on structures built along rivers, agricultural lands, etc. Rivers have been one of the most important factors in the geomorphological processes of the land and the erosion cycle, and so far, extensive studies have been conducted on the morphological changes of rivers and the factors affecting them. The instability of the river channel and its sediments not only destroys the marginal lands and facilities adjacent to the river bank, but also the sediments caused by erosion in some cases include a significant amount of the total sediments that the river flows.

The morphology of a part of Qarachai river in Markazi province of Khondab city from the top of Shaveh village to the bottom of Farab village, with a length of 12 km has been studied. First, the location of the Qarachai River watershed and the study area have been determined using digital topographic maps and ArcGIS10.2 software. Then satellite images and aerial photographs of the study area, which are the most important tools for studying changes in river paths, have been collected in two time periods. In the following, the aerial photos scanned in Photoshop software are photomosaic and are referenced in ArcGIS10.2 software using fixed points such as villages, bridges, etc., using aerial photographs of the year. 1968 Satellite images of Landsat sensor of 2021 have been digitized in two time periods in ArcGIS10.2 software environment.
 

Changes in wavelength and valley length in the two time periods studied in the study section of the river show that in the study area, the morphology of the river has not undergone major changes and the curvature of the study area has not changed much. The study of changes in wavelength and valley length and arc length in the two periods studied shows that the average wavelength in 1968 is about 413.25 and in 2021 is about 387.63. The wavelength in 1968was longer than in 2021. The changes compared to the 53-year period are about 6.2% and very small. As the wavelength decreases, the distance between the windings also decreases. The changes in the length of the valley relative to the meanders. The average length of the valley in 1968 is about 224.46 and in 2021 is about 12.21. Changes in the two timelines are about 5.5% and are very small.

The general pattern of the river from 1968 to 2021 has not changed significantly and is always twisting. The number of windings during 53 years is the same as 23 windings. The fact that the number of meanders is constant indicates that there is no change in the morphological pattern of the river. The results of extraction and statistical comparison of geometric parameters of this part of the river such as wavelength, sine coefficient, width to depth ratio, etc. show that the sine coefficient of the river from 1.5 to 1.3 The wavelength and radius of the tangent circles on the twists and turns have also increased. The average curvature coefficient in the 40s is about 1.11 and in 2021 is about 1.08. According to the division table of rivers, this period studied by Khondab river has a sinusoidal state and has not changed much in two time periods.

Accurate estimation of river suspended sediment load (SSL) has an important role in water resources, watershed management and related sciences. Due to the high fluctuations of SSL in different seasons of the year as well as its severely nonlinear and complexity nature, it is necessary to use appropriate methods that can simulate and estimate such phenomena.

In this study, data log transformation and multi-objective particle swarm optimization (MOPSO) algorithm were used for optimal training of neural network models. For this purpose, at first, by using unsupervised neural network (SOM), data of flow discharge and suspended sediment load of the studied hydrometric station (Statistical Period 1995-2016) were clustered. Then, by sampling the clusters, the data set needed to train and test the neural network models were prepared. After it, three scenarios were defined to evaluate the impact of applying logarithmic transformations and MOPSO optimization algorithm In the first scenario, the initial data (without logarithmic transformation) and the common base gradient algorithm in training neural network models (error propagation), in the second scenario, the error propagation algorithm and the logarithmic transforms, and in the third scenario, the logarithmic transforms and the MOPSO algorithm, was used to train neural network models.

Evaluation and comparison of the model validation results showed that applying a logarithmic transforms and MOPSO algorithm, by reducing RMSE error and bias percentage (PBIAS) from 49 ton/day and -21%, in the best model of the first scenario, to 30.3 ton/day and -6.3%, in the best model of scenario III, increased the efficiency of the models. Other results of the study are non-estimation of negative values for suspended sediment, which is one of the common errors in using neural network models in estimating suspended sediment.

The use of multiple objective functions makes it possible to sensitize the models to more accurately estimate the suspended sediment at low or high flows, thus improving the validation and skewness indices of the base data models.

Aim of this research was Studying and Recognition of lithology and Erosion Rivers in Sistan region. To done this research distinct situation of rivers according of basin and collected inform about basin of Sistan and review different parts of them such as type of erosion in river banks by using available reports and filed works. We have used available scale of 1:50,000, 1:250,000, Geologic maps, field observation and global positioning system (GPS). We found erodible area of river banks according to scale of 1:250,000 erodible Geologic maps. The data show that’s the main factor of cause to erosion is effect geologic conditions. The main parts of the basin covered with sediment of quaternary which is very sensitive to water erosion. The sistan rivers classification shows that stone, alluvium and other are 20.7, 38.1 and 41.2 percentage of rivers length, respectively. 7.2 percentages of area rivers occur erosion that bed and banks erosion are 85.1 and 14.9%, respectively.

Floods cause erosion and sequestration of sedimentary material in rivers, and each of these factors causes deformation in river morphology. This change in shape annually damages the activities of the residents of the riverbank and its adjacent facilities, and it also presents problems along the river. In this regard, erodibility detection and zoning in a river is one of the issues that will be used to manage and control river erosion. This study was done on a 15 km downstream reach of Ghezel-Ozan River in north of IRAN. This part of the river in terms of geomorphology, is an alluvial river with fine to coarse bed material and due to geometric, hydraulic, geological and bed and side material conditions. Then the IRS and Landsat satellites images as well as aerial photos from 1968 to 2010, the plan and pattern of river displacement in GIS environment were investigated. In this study, after dividing the study area into 10 different intervals, the location of the riverbanks and river displacement widths at different time points, and the critical or degraded or deposited critical areas in each interval were determined. In addition, using factors such as soil moisture uptake capacity, vegetation cover and soil texture of the studied river margin as well as the hydraulic properties of the flows occurring, the factors affecting erosion at different intervals of the studied river were analyzed. Investigations of river deformation and geometrical characteristics of the river showed that the Ghezel-Ozan River at 9.95 km was in the range of sinusoidal and meandering coefficient, and approximately 85% of the windings were in the range of meandering coefficient of 1.06 to 1.5. The number of Meander in the study period has decreased from 19 Meander in 1968 to 15 Meander in 2010.According to the criteria of the central angle arches, the most frequent central angle within this range (40%) were ranked in categories relating to meander developed 158-85, And the highest angle in 1968 is about 139 degrees and in 2010 is about 182 degrees and so this area is from the Ghezel-Ozan River, a young and dynamic Meander river. The results showed that the most unstable reach in the multi-thickness region is in the 5th reach. Decreasing the slope and decreasing the hydraulic power of the river have caused a multifaceted phenomenon in this area. The average radius of Meander was higher in 2010, due to the erosion of the riverbank, which is often alluvial and marl, indicating the radial development of Meander. Comparing the central line of the river in 1968 and 2010, it was also observed that there are different states of coastal erosion and shortening in the meander rings. Hydraulic factors associated with the instability of the banks along the river can be the erosion of the under of the walls due to the high velocity of flow at the bottom of these walls and its fall, and the occurrence of gully erosion over the walls due to inadequate drainage of farmland.

This study investigated the status of sediment transport and deposition in Khar-rud River، Qazvin province، Iran. The aim was to determine the possibility of construction of sand and gravel mining workshops in the margin of Khar-rud Flood-plain. Here with calculating sediment transport rate and specifying the distribution of sediment deposits in various parts of the river، an applied program for sand harvesting from the river bed، is developed. In this project، after preparing the basic information، such as information about river geometrical shape، roughness coefficients of different sections، information related to size gradation of suspended sediments and bed material، river hydrology data and boundary conditions of downstream hydraulic system، using HEC-RAS model، sediment loads and its distribution along the river was simulated. Simulation was done based on classified data from daily flow discharges during a 37-year period. After calibrating the HEC-RAS model and selecting Yang sediment transport equation as the closest relationship to the sedimentary data measured by regional Hydrometric stations، the average volume of sediment yield from the river was estimated 1. 75 million tons per year. Finally، considering the changes in the river bed elevation for each cross-section، the amount of sediment passing during simulated 37-year was calculated. Using the results of the model and sedimentation changes along the study reaches، the volume of sediment transport in each river cross section، the river width and its private region and considering the maximum permissible depth of bed-material removal equal to 1 m، the most suitable mining length and period in the different reaches of river was determined، discussed and showed in ARC-GIS environment. Based on simulation results، the average depth of sand which can be taken safely from the river-bed was estimated to be 40cm and the most suitable period of time for sand mining along the river was recommended from January to May. It was determined that HEC_RAS hydraulic model، covers about %63 of initial engineering judgments for the amount and location of sand mining.

Bottom outlets are series of structures that were used to convey water from dam reservoir to the downstream. Due to the importance of Bottom Outlet Systems in dams، analyzing the performance of conduit،gates and outlet is considerable. The existence of high-pressure flow in the bottom outlet channel، the various kinds of head losses and the small amount of opening height versus the reservoir head over the gate cause considerable errors in the required mathematical methods and relationships. Therefore the need for laboratory studies in this regard is essential. The purpose of the present study is to determine hydraulic capacity of Narmasheer Dam Bottom outlet using data obtained from physical model. In this research، the physical model of bottom outlet system of Narmasheer Dam including conduit، gates (service and emergency) and outlet was designed and constructed at SCWMRI (Soil Conservation and Water Management Research Institute) lab، and then the necessary tests have been performed. The different amounts of pressure heads and water discharges in various gate openings were measured for 6 different head of reservoir and 12 opening gate. Results showed that the trend of discharge Hydraulic coefficient in maximum head، from 2 to 10 percent gate opening، had an increasing rate and for 10 to 30 percent opening، had a decreasing rate and then from 30 to 70 percent opening، will be increased with smooth rate، and finally in more than 70 percent in gate opening، will be increased with an accelerated rate. This process was tested in other heads of reservois، but trend of discharge coefficient will begin to increase from 50 percent gate opening. Overallchanges in coefficient Cd show an increase amount of valve coefficient for gate opening، Cd. It is worth to mention that with an increase in opening gates، the rate of discharge will also increase.