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

The use of structures has economic and safety advantages compared to other energy-consuming structures. In this research, to investigate the effect of the length of the sill of the flip bucket spillway on the scour downstream, experiments were conducted in a rectangular laboratory flume made of Plexiglas. The scouring downstream of the flip bucket spillway was investigated using a flip bucket spillway with four relative sill lengths and four threshold angles at four current intensities in the channel in this research. The results of this research showed that by the increase in the length of the sill in the flip bucket spillway, the energy consumption in the spillway increased and the scour depth downstream decreased. Also, increasing the relative length of the sill by 70% at the sill angle of 45 degrees, the scouring depth is reduced by about 88%. Also, a relationship was presented to determine the maximum depth of relative scour, and the correlation coefficient of the results obtained from this equation with the laboratory results is about 0.92.

Piano key overflows have a high discharge capacity. Proper design of these overflows requires sufficient accuracy in predicting the type of overflows. In this study, experiments were performed in a rectangular laboratory flume made of Plexiglas to investigate the effect of the relative length and width of the two-cycle piano switch overflow crest on the discharge coefficient. In present research, the flow intensity coefficient was investigated by installing a rectangular piano switch overflow with relative crest lengths of 0.8, 1, and 1.2 and relative crest widths of 0.2, 0.3, and 0.4 in 10 flow intensities in the channel. The results of this study showed that by increasing hydraulic load, the flow intensity coefficient first increases and then decreases. Also, by increasing the relative length of the crest by 50%, the current intensity coefficient increases by 43% in the overflow. Increasing the relative width of the overflow crest by 50% increases the current intensity coefficient by 25% in the overflows. Also, an equation was presented to determine the maximum relative scour depth, and the correlation coefficient of the results of this equation with the laboratory results is about 0.90.

Drought is a phenomenon that in addition to the lack of water resources, causes decrease in the quality of surface water. The purpose of this research is to investigate the effect of drought on the water quality of Kashfroud river. In order to, precipitation, temperature and quality data of six meteorological and hydrometry stations were used during the 30-year statistical period (1989-2019). Calculated SPI and SPEI index, drought and wet were selected among all stations. The changes of water quality parameters were investigated in the statistical period and the drought and wet period. The results showed that the average quality parameters of water have changed significantly during drought. In all stations, the concentration of TDS, EC, Ca, Mg, Na, SO4-, HCo3-, and Cl- have increased in the drought period compared to the long-term average. Its maximum for Cl-parameter is 7.66 mg/l at Olang Asadi station. On the other hand, during the period when drought indicators increased and drought occurred, the value of this parameter decreased by 32.73%.Due to the increase in temperature in drought period and the increase in EC value, the highest percentage of changes is in Olang Asadi station with 70.73% and the lowest in Golmakan station is 1.75%. Based on the results, the average concentration of cations and anions in Olang Asadi station shows an increase of about 5 times compared to Golmkan station.Finally, it can conclude that the decrease in rainfall, increase in temperature and drought, the water quality has decreased, especially in the downstream stations.

It is necessary to use mathematical models to determine the river's response to pollutants. These models are able to simulate the effect of existing and future pollutants and facilitate related decisions. In this study, the water quality of Dez River and its main feeding drains were extracted and analyzed through sampling and laboratory analysis from Dez diversion dam downstream of Loreh drainage during seven months from March to September 2018. The results of the measured samples were compared with those of the simulated values through the HEC-RAS model. The river path was investigated in the study period and seven sampling stations were determined along the river and six stations at the point of drainage into the river to determine the sampling stations, as well as the sources of pollution of Dez River. The results indicated the lack of self-purification of DO, BOD, NO3, NO2 parameters in Dez River during seven months of 2018 due to the inflow of drains and lower river discharge in this period. Also, the base on NSFWQI index, in drought seasons the first half of the river quality index is less than 68, that indicates average quality, and in the second half of the river, the quality index is less than 50 (poor quality). This decreasing trend of NSFWQI quality index is consistent with the trend of qualitative variables of HEC-RAS simulation and indicates the lack of relative self-purification of the river during the study period.

Long-term recognition of river water quality and quantity is important for examining changes in the past and predicting the future. Therefore, in this study, qualitative and quantitative changes in the water of the Polroud River in Guilan province have been investigated using graphical methods and statistical analysis. In this study, the recorded data of water quality variables in from 1999 to 2018 were used. Schuler diagrams were used to evaluate drinking quality, Wilcox for agricultural quality, Piper to use water type, and Mann-Kendal method to examine time series and Pearson correlation test to examine the relationships between parameters. According to the results obtained from the Schuler diagram, the water quality of the River is in a good condition in terms of drinking and for the seasons of Spring, Summer, Autumn and Winter. The results of the Wilcox diagram show that the river water quality is agriculturally in a good and suitable condition and the results of the piper diagram show the water type is calcium bicarbonate. Also, according to the Mann-Kendal test, there is an increasing linear trend in the annual flow of the river. The results of qualitative statistical analysis of the parameters studied in this study in the period from 1999 to 2018 showed that in the summer the measured parameters have high values compared to other seasons so that the highest mean for the EC index in this season is equal to 290.85, TDS was equal to 246.3, PH index was equal to 7.65. Also, in the flow study, it was found that the highest flow rate is related to spring with a rate of 30.82 m3/s and the lowest in summer with a rate of 10.73 m3/s. The results of Pearson showed that there is a direct and significant relationship between EC and TDS.

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.

Rriver pollution due to various urban and industrial wastewater and agricultural effluents is a serious threat to human health and aquatic ecosystems. Therefore, surface water quality assessment is one of the main indicators of sustainable resource management. The present study was conducted to evaluate the water quality of Karun River (in Molasani and Ahvaz Stations) during 1397 using two indicators, IRWQI and WAWQI. Also, various physical, chemical and biological parameters of water were statistically analyzed. An examination of both indicators' value shows that the river situation in downstream is declining due to the entry of industrial wastewater, especially agro-industrial units, sugarcane factories and thermal power plants along the river. The results show that the river water quality according to WAWQI index in Malasani and Ahvaz stations is in poor and very poor category and according to IRWQI index is relatively poor. The WAWQI index related to Ahvaz station in May (85.89) and Mollasani in July (49.04) is in the worst and best condition. Also, IRWQI index in the lowest and highest quality level is related to Ahvaz station in December (32.75) and Malasani station in July (42.51). Therefore, based on the results obtained from quality indicators, it can be concluded that the WAWQI index is slightly more conservative in classifying water quality than the IRWQI index. Also, due to the high values ​​of fecal coliform parameters, TDS and turbidity in both stations, water is not suitable for any of the drinking, agricultural and aquatic ecosystem uses. The statistical analysis the sum of anions and cations with 0.46% and fecal coliform with 24.14% have the lowest and highest portion in WAWQI, respectively. This study shows that TDS in river shows a strong correlation with sodium and chlorine.

Sediment control is one of the issues of paramount importance in designing irrigation networks and water supply facilities. The most important methods of erosion and sedimentation management and control include basin management, sediment trap management in upstream, and sediment trap source management out of the river. Jafari et al. (2019) investigated the effect of submerged vanes and their dimensions on the bed load transport in the widened part of the river using a laboratory model. The results showed that by increasing the dimensions of submerged vanes, the speed of the bed load transport decreased, and as a result the performance of vanes improved. In a similar research strand, the present study evaluated the effect of obstacle installation and its size in the widened part of the river on the bed load transport using a laboratory model.

Using a dimensional analysis of the effective variables in the widened part of the river and installing obstacles, this study identified the influential parameters on the bed load transport. Some experiments were then carried out by simulating the widened conditions of the river in a laboratory canal. Then, a witness experiment was carried out in the widened part of the river without the presence of an obstacle. This was followed by 21 experiments in the widened parts of the river by installing an obstacle. Linear obstacle arrangement in the basin was then performed in 5 rows and 3 columns and it was considered constant for all experiments. Moreover, the discharge rate and depth, according to the initial experiments and the amount and manner of sediment movement, were constant for all experiments and equal to 10 liters per second and 0.16 meters, respectively. In order to examine the effect of the obstacle size, 15 obstacles with 0.04 meter height (hb), different width (Wb) and length (Lb) with 0/02, 0/03, 0/04 and 0.05 meters were installed and tested. At the end of the performance, the main section (i.e., the widened part) of the bed load control was examined quantitatively and qualitatively. To examine the quantitative performance of the main section, equation (1) was used. Rs = (1) In (1), Rs is the reduction in the distance of sediment flow in the widened part with an obstacle relative to the state without an obstacle (i.e., witness test), xe is the progression of sediment flow in the widened section without an obstacle, (xe- xb) is decreasing the progression of the sediment flow in the widened part with an obstacle relative to the widened conditions without an obstacle.

Integrated operation of surface water and groundwater resources is one of the most important challenges facing water resources researchers. Integrated use is, in fact, the exploitation of surface and groundwater resources in order to increase the amount of available water and the sustainable use of available water resources. Therefore, one of the main goals of the present study is to simulate the interaction of surface water and groundwater by creating a dynamic couple between the WEAP surface water model and the MODFLOW groundwater model in the Miandarband plain. In this regard, the Soil Moisture Hydrological method was used to simulate the unsaturated zone of the soil. The results of simulation of surface and groundwater interaction were presented and the conditions for the use of water resources in the area was investigated for the continuous current policy. One of the most important achievements of this research is the simulation of saturated and unsaturated zones of the soil using complete hydroclimatology balance components as a coupled model of surface and groundwater. In the period of 6 years, the highest amount of aquifer recharge in the Miandarband plain, is about 10 to 19 million cubic meters in November to March. In some of these months, in addition to rainfall, the aquifer recharge is due to the infiltration of irrigation water. The highest rate of groundwater drowdown (7.5 meters) is related to the northern part of the plain and the average drowdown in the whole plain at the end of the 6-year operation period (October 2007 to September 2013) will be about 4 meters.

The occurrence of scouring is one of the most important threats to the stability of the bridges which built on the rivers. In order to prevent possible destruction and irreparable damages, it is necessary to control scour by carefully examining the scouring process and applying appropriate methods. In this research, by constructing a laboratory model, the effect of using a simple spur dyke on the reducing of the scour around the bridge abutment which located on the erodible river bed was investigated. For this purpose, a spur dyke structure with certain dimensions and specified distance from the bridge abutment (according to the flow characteristics of river geometry) was used and the effect of each parameter on the scouring of the abutment was examined. Also, based on statistical analysis using the SPSS software a regression relationship achieved for estimating the scour depth around the abutment. The results of this study indicate that the protective spur dike reduced the scour depth around the bridge abutment nearly 94%. Also, the efficiency of the spur dike was directly related to its length and inversely related to its distance from the abutment.

The geographical map of the countries shows that the political boundaries are not aligned with the water basins. The existence of transboundary rivers has led to divergences over the water availability of these rivers in many countries. Competition and conflict have been created for gaining more profit. What makes the competition over the border waters more serious is the nature of the international relations of the upstream and downstream Countries that transform water use into political leverage. In Iran, the limitation of fresh water resources and the need to plan for the proper utilization of diverse water resources capacities, highlight the importance of obtaining the right of transboundary rivers. This part of the water is effective in preventing pressure on internal resources, some natural damage caused by drought and water scarcity, and some internal conflicts between basins. Considering the research done on transboundary rivers, which have often been politically or geographically examined, So far, no research has been conducted on the development and prioritization of strategic policies for the extraction of the water rights of Iranian transboundary rivers. In this study, the strategic policies that the government can adopt to obtain the water-right of the Iranian transboundary rivers were determined based on the expertise of experts in the fields of water sciences, environment, geomorphology, political sciences and middle managers of the water industry. To this aim, a questionnaire was prepared in with 5 Criterion and 12 strategies. Then, its validity was evaluated by the relevant experts. After conversion of qualitative values to 20 quantitative questionnaires, the reliability of the questionnaire was confirmed by Cronbach's alpha in SPSS statistical software. This coefficient was calculated 0.735. The AHP method was then prioritized by Export Choice software. The ANP method was prioritized in the MATLAB programming environment. Then, the results of both methods were compared. In the sensitivity analysis by the Three Antifilo method, the numerical value of the most sensitive criterion was calculated and then the weight of the other criteria was modified accordingly. The threshold percentage and change in weight of the criteria were determined. Afterward, the sensitivity coefficient of the criteria was calculated and the numerical value of the most sensitive criterion was modified. The other criterion was modified based on the modified critical criterion. To analyze the sensitivity of strategic policies the fallowing steps were taken: First, numerical values of threshold weight and its percentage and critical degree were calculated; Second, sensitivity coefficients of strategic policies, which are the inverse of the most critical strategies, were calculated and compared; Third, The numerical value of the most sensitive strategy was corrected; and at the last step of this method, the values of each strategic policy were normalized to the most sensitive criterion. The results showed that the two criteria of benefit and timing with weight of 26.26 and 0.13 were in the first and last priority, respectively. The final prioritization was similar in both ways, except in the second, fourth and ninth strategy of the initial table. The strategy of controlling more outflows from the country and applying pressure to reduce tariffs for importing high-quality virtual water into the country, in the AHP method with 11.88% and in the ANP method with 11.08%, placed as first priority. In addition, A11 strategy was the last priority with 8.17% by AHP and 6.11% by ANP. Also, profitability with the coefficient of 0.185 was introduced as the most sensitive criterion. Based on it, the weight of the other criteria was modified. Therefore the prioritization of the criteria remained unchanged in comparison with the results of the sensitivity analysis of strategies based on each criterion separately. It showed that the most sensitive strategic policy is the strategy of cooperating with neighboring countries for better access to seawater, changing the pattern of cultivation with low water requirement and thriving in other economic potentials of the neighboring country to reduce the tendency for highly water-intensive activities. Its regarding coefficient was 0.178 which is the highest value, based on the profitability criterion. In the final step after normalizing the weights of the strategies according to the critical criterion, the prioritization of the strategies with little change in weights also remained unchanged. Advancing the first policy will be effective in short term, but will not entail economic costs, and it may create political strain on the diplomatic relations of the two countries. Advancing the second priority will be more time consuming, but not, economically and politically costly. Like the first priority, the second can improve Iran's political standing in the region, while it can cost diplomatic means on the country. The last priorities are the strategic policies that are economically costly for the country and have a negative impact on the other two countries' relations.

Pipelines passing across the river to convey water, gas, and petroleum may develop local scour at the pipeline location. Scour development may cause damage due to pipe failure and disorder in utilization. The eddy currents around the pipe lead to the scouring phenomenon causing the non-uniformity of the pipeline and its fracture which will ultimately have environmental and destructive consequences. In this study, the effect of pipe diameter has been investigated. The experiments were conducted with five diameters (20, 30, 40, 50, and 60 mm) in three Froude numbers (0.2, 0.235, and 0.26) under identical bed conditions. In the following part, scouring profiles were taken and the scouring progresses over time and maximum scour depth were investigated. The results show that scouring under pipe for a diameter of 60 mm has the highest and is the most progressing towards time compared to other diameters.

Hyporheic zone is an active area that groundwater and surface water are mixed together in that zone. Any existing contamination in the surface water can be transferred to groundwater through this zone. In this research, the hyporheic zone beneath Zarjoob River and above Foomanat Aquifer was investigated by modeling to understand the impact of river on groundwater quality. For this purpose, three stations and three nearby groundwater wells were selected and water samples were collected in Year 2006-2007. The hyporheic zone was modeled for TDS as conservative parameter and NO3 as non-conservative parameter. MODFLOW and MT3D were used to simulate TDS in the hyporheic zone in two seasons; the agricultural season and non-agricultural season. The results showed that the hyporheic zone in non-agricultural season is 20 m far from the river, while in the agricultural season it was significantly less than 20 m. The results also showed that the reduction rate of TDS in agricultural season was more than that in non-agricultural season. This could be due to more groundwater use and increase in groundwater flow velocity. In the next step, NO3 was simulated using MODFLOW and RT3D. The simulation was carried out for two scenarios; with and without biodegradation. The results showed that without considering biodegradation, the hyporheic zone would extend to 25 m far from the river while with biodegradation it would be reduced to 20 m.

Several factors affecting pollutant transport in rivers. Among those, vegetation is less studied by researchers. Due to the appropriate conditions in floodplains, such as adequate moisture and fertile sediments, it is possible to develop and grow different types of vegetation in these areas. Depending on the type of vegetation, their effect on the flow and subsequently on mass transfer is different. In this paper, the effects of flow depth, vegetation arrangement, and the interaction between the floodplain and the main channel on the longitudinal dispersion coefficient, K, in a compound channel has been studied. The results show that K is greater in the main channel rather than the floodplain. In addition, the interaction of the main channel and floodplain increases the K values up to 30 and 88% for non-vegetated and vegetated conditions, respectively, which are statistically significant. Similarly, the effect of vegetation arrangement on the K values are statistically significant, and K /U*iHi is greater for the staggered arrangement rather than tandem arrangement.

Understanding water budget components is crucial for making decisions regarding water resources planning and management. Surface water–groundwater interactions are commonly investigated at the river reach scale and generally classified as connected or disconnected type systems. Connected systems are either gaining surface water system, where groundwater discharges through the streambed to contribute to streamflow, or losing surface water system which loses (or recharges) water to the local groundwater system. Disconnected systems are defined by an unsaturated zone beneath the surface water system which loses water at a rate related to the hydrogeological properties of the streambed and the aquifer. These interactions have significant implications for both water quantity and quality. Seepage of fresh groundwater into a river can be important in maintaining flows during extended dry periods. This can be critical for supplying the needs of surface water users such as irrigators as well as for aquatic ecosystems. Pumping from an aquifer near a river can dramatically change the amount of this base-flow to the river. In contrast, if the groundwater is contaminated, increased groundwater discharge can have a negative effect on river water quality. The Bojnourd catchment is located in North Khorasan province. The catchment covers an area of about 1265.8 km2. The main river in this area, Firouze River, is approximately 10 km in length, and is hydraulically connected to the Bojnourd alluvial aquifer. The alluvial aquifer of Bojnourd plain with 65.2 km2 area is mostly covered by urban area. Hence, effective management of water quantity and quality issues in the Bojnourd catchment requires quantifying flow between surface water and groundwater. Furthermore, conveying water from the outside of basin caused water table to rise which made some problems for urban buildings and infrastructures. Therefore, the river and aquifer interaction needs to be studied more comprehensively.

Numerous techniques and methods are available to describe and quantify the flow between surface water and ground water. This study combined two methods, numerical modeling using MODFLOW code and reach measurements, to quantitatively evaluate groundwater/surface water interactions under highly transient conditions. The groundwater flow system of the study area was conceptualized based on borehole logs, pumping tests, and available hydrogeological and geophysical information. Moreover, field work, including measuring streamflow in three seasons, was carried out to conceptualize and quantify the groundwater/surface water interactions. Following the conceptual model, the numerical model was developed to simulate flow through the system. The model grid had 1274 active cells with a uniform cell spacing of 250×250 m. The water exchanges between the main regional river, Firouze river, and Bojnourd aquifer was simulated using the River (RIV) package. Both hydraulic head target and flux target were used to calibrate the model. The head targets were compiled from the monitoring network which contains 11 observation wells. The flux targets were located in three measurement points along the Firouze river. The data obtained from the fieldwork were used as observed values for the groundwater/surface-water exchanges. The transient model was calibrated and validated for 15 hydrological years, i.e. from 1 October 2001 to 1 October 2016

Model performance was evaluated using root-mean-square error (RMSE). The model results were in agreement with corresponding observed data, including groundwater heads and measured groundwater/surface-water exchanges. The RMSE values during calibration and validation periods were 0.83 m and 1 m, respectively. Analyzing water balances resulted from transient simulation showed that Firouze river is gaining in some reaches and losing in other reaches. In losing reaches, the total flux into the aquifer is 6.4 MCM per year. In gaining reaches, the volume of groundwater discharges through the streambed is about 4 MCM per year. Furthermore, the effect of several management scenarios, including continuing the existing condition, turning the domestic wells off and implementing a sewage system by 2025, on groundwater heads and groundwater/surface-water exchanges was examined using the numerical model. Results showed that by implementing the sewage system, the volume of water discharged to the river would decrease, but it will prevent aquifer and river contamination caused by sewage water. 

In this study, groundwater budget components in Bojnourd aquifer including groundwater/surface-water exchanges were calculated. The results showed that understanding of these surface water-groundwater interactions, which has been ignored in previous studies, is important for effective management of water quantity and quality issues in Bojnourd plain. Moreover, the methodology used in this study including numerical modeling and measuring flow at multiple points along the stream is effective and easy to apply to estimate the direction and magnitude of seepage on a stream reach basis.

In general, rivers are one of the best and most accessible water resources at the disposal of mankind.  So, given the effect of the force of water and changes on the  flow patterns and consequently, on river morphology changes, the analysis of the flow in the river is important and necessary to organize projects, flood control and water supply structures downstream. In this study, by using numerical models CCHE2D hydraulic conditions Dimeh River Bridge between Oregon Bridge Sudjan was investigated. CCHE Model is a mathematical model capable of simulating the flow patterns and sediment transport in rivers and canals laboratory network. The numerical model in 1998, based on the calculations by the National Centre for Water Science and Engineering, University of Mississippi (NCCHE), was developed and has been applied in many research projects related to water engineering. At the outset, the input data required model provides and numerical model was implemented. In the next step, the results of the model were calibrated and validated using field data measurements; eventually, they were extracted and their model results were compared; it was confirmed that CCHE model could still simulate the flow pattern.

Bridges constructed across rivers are among the most important structures, especially during and after flood events. Bridge piers are exposed to some hazardous factors such as local and contraction scour hydrodynamics. The lower prediction of maximum scour depth can cause  bridge failure, while over-prediction leads to a very costly project. The appropriate estimation of maximum scour depth around bridge piers is, thus, necessary. In some bridges, more than a single pier is considered during the design phase, and the interaction between the adjacent piers makes the situation very different. The flow structure and scour process around a group of bridge piers are, indeed, very different from a single bridge pier. Many researchers have studied the scour around single and/or multiple-column bridge piers. For instance, studying the scour depth for a group of piers, Mahjub et al. (2014) reported that the maximum scour depth around the second bridge pier was less than that of the upstream pier, while the scour depth around the third pier was lower than that of the first and second piers. Moreover, Daneshfaraz et al. (2014) investigated the effect of pier slots on the maximum scour depth around the two-column bridge piers. The results that the slot reduced the maximum scour depth compared to the piers without a slot. In this paper, the flow and bed topography around a group of piers was studied experimentally.

The scouring of river bed around bridge is one of the most important issues in bridges destruction. It has been found that the occurrence of scouring on the bridges abutment is the most important cause of the destruction of bridges in all countries. Among the techniques of reducing scouring around the bridge abutment which are called “indirect measures” is to modify the flow pattern and reduce the power of vortex vortices which are the main cause of scour. At the present study the performance of immerse vanes was investigated at a constant distance of 2 times of the abutment effective length and 4 different angles under four different flow conditions (Froude numbers= 0.15, 0.17, 0.2 and 0.22 (. The destruction of immerse vanes is impossible due to the installation of them above the bed and within the depth of the flow. As a result, the main purpose of this study is to determine the most suitable angle of displacement of the vanes in the upstream of the bridge abutment, which will cause the least scouring.

The experimental tests were conducted in a flume of 8 meters long and 1 meters wide. A rectangular abutment was installed at the middle of the test section (2 meters long) covered with bed of fine sand. Each test started by turning on the pump, which transfers the flow from the reservoir below the laboratory. The water flows through the flume after passing through a net that is filled with fibers in order to depreciate the flow fluctuations. At the end of the flume, after passing through the sliding valve, the flow into the pool was collected. At the end of the pond, a 53-degree triangular overflow was placed in order to measure the flow rate, which then flows into the underground reservoir. At the beginning of each experiment, after the leveling of the bed by opening the opening at the beginning of the flume, the flow gradually entered the flume so that the sediment would not be destroyed. After increasing the water level in the flume, the flow rate slowly increases to reach the desired flow rate.

In this study, bed topography was taken for all experiments using laser meter and then plotted using Surfer software. The results showed that in all experiments, maximum scour depth was observed in the upper nose of the abutment, and with increasing flow conditions, due to increased bed shear stress and the power of vortices around the structure, the maximum scour depth and scour hole volume increased. Also in this study, it was found that the angle of installation of the immerse vans has a great effect on the performance of the vanes in reducing the depth, surface and volume of the scouring hole. Generally, it shows that use of immerse vanes have been reduced scouring significantly compared to the case of no vanes.

The most effective angle of installation was found to be equal to 65 degrees, which, on average, reduced the maximum depth of scouring, lenght and width by 66, 71 and 69 percent, respectively.