نشریه دانش آب و خاک
سال بیست و ششم شماره 2 (تابستان 1395)

Scour generation and its development around bridge piers are the main causes of bridges damage and failure. Understanding the scour mechanism is essential to predict the scour and equilibrium scour hole status around bridge piers. In the recent decades, the use of compound bridge piers instead of the simple piers in construction of bridges, has been developed. In this study, using the FLOW-3D software, process of the formation and development of the scour around bridge pier with compound geometry has been investigated. Numerical results obtained from this model were compared with available experimental data. The results showed that this model had the capability to predict the threedimensional flow field and could effectively provide a better understanding of the experimental studies. The results also indicated the complexity of turbulent flow near pile cap so that these flows were deflected in all directions. On contrary to the simple pier, in which the positive maximum velocity occurred in the sides of pier, in the case of piers with compound geometry this velocity occurred in the center of the pier and downstream of the pile cap.

Floods inflict a large amount of loss on communities and installations in Iran due to the geological characteristics and environmental destructions. Detention rockfill dams are important structural methods to mitigate flood damages. So, it is necessary to assess the optimum characteristics of detention rockfill dams considering their hydraulic performance. In this paper, a novel methodology based on data-driven simulation model, NSGA-II multi-objective optimization model and game theory is suggested in order to find the optimum features of detention rockfill dams. The proposed model is on the basis of the multi-objective genetic algorithm model (NSGA- ΙΙ) and the multilayer perceptron neural network meta-model (MLP). The MLP meta model simulates the relationship between design variables of detention rockfill dams and the hydraulic parameters of flood hydrograph passing through the porous media of the dam. The MLP based simulation model is trained and validated on the basis of experimental results of a physical model of detention rockfill dam. The validated MLP model is then coupled with a robust multi objective optimization algorithm, NSGA-ΙΙ, to determine the trade-off curve between the conflict objectives of the optimization. Nash- Harsanyi bargaining model and Borda count social choice method are used to find the best agreed-upon design point on the trade-off curve of the optimization objectives. Results indicate that the optimum design variables can be considered as [27.1, 27.58] cm and [2.02, 4.52] cm for the optimum thickness of detention rockfill dam and the optimum diameter of aggregates in the porous media, respectively, using both the mentioned methods. The similar optimum characteristics of detention rockfill dam using Nash bargaining model and Borda count social choice method depict the stability of the applied methods.

Canola plant production is the source of 15 percent of the world total vegetable oil production which is the third largest seed oil production after soybean and oil palm. The objective of this research was to identify the suitable areas for planting Canola in West Azerbaijan Province, Iran. Hence information on climatic data from 67 weather stations were collected and analyzed. Climatic data such as temperature, precipitation, degree days, relative humidity, number of frost days, and sunshine hours were colleded from synopotic and climatological stations, and also gauge resource data such as topography, slope, slope direction, soil depth, and land use were prepared. Each of these data was studied regarding to favorable climatic and ecological needs of Canola. Information layers on each of them were made by data generalization to layers and processing them using GIS technology. In this research, multiple criteria decision method (MCDM) based on AHP method was used in order to prioritize, and assess the criteria and information layers regarding each other, and determine their weight. By weighting the provided layers based on intended criteria and model, layers were overlaid and special analysis was done in GIS system and the final map of assessment of land capacity was generated for Canola cultivation. According to the results, lands of the Province in terms of climatic and environmental potentials were categorized into four levels: very suitable 15.2 percent, suitable 52.1 percent, average 25.4 percent, and weak 7.3 percent.

Measuring the precision quantity of soil moisture in agricultural science is very important. Therefore, it is important to have accurate and fast measurement of soil water content, especially to achieve soil characteristics by a non-invasiveness way. In recent years, application of time domain reflectometry (TDR) as a well-known for measuring soil water and electrical conductivity in short time has been common. The objective of this study was to evaluate the accuracy of the TDR probe under laboratory conditions in clay and sandy soils at four soil salinity levels of 2, 6, 12 and 18 dS m-1 which were packed in a PVC cylinder with 27 cm in diameter and 300 cm in length. The TDR underestimated dielectric coefficient and volumetric moisture in heavy soil due to the effect of bound water in heavy soil which reduced the time delay. Also soil dielectric coefficient increased with increasing soil salinity, resulting in overestimation of the soil moisture. The result of soil salinity and texture interaction showed that under high soil salinity levels (12 and 18 dS m-1) the estimated moisture by the device was less than the volumetric method, whereas under low soil salinity it was vice versa. This indicated that in high salinity level, the effect of clay caused the low estimation of soil water content but in the low soil salinity level, electric conductivity would lead to over estimating moisture content.

Slope characteristics (aspect and position) and parent material are effective factors on soil properties. This research was conducted to study the soil physico-chemical properties formed on north and south faces as well as back slope and summit positions which developed on two selected parent rocks such as peridotite and pegmatite in Masouleh area. Thus, 6 representative soil profiles in different positions and aspects were dug and described and then, the soil samples were taken from the two depths of 0-15 and 15-30 cm in 3 replicates from distances of 10-20 meters around the soil profiles. Physico-chemical properties such as soil texture, pH, organic carbon, exchangeable cations, cation exchange capacity (CEC), amorphous and free iron oxides were measured. The results showed that the soils formed on the different parent materials had significant differences (p

Determination of flow resistance is an essential parameter for studying and hydraulic analysis of the open channels. Manning roughness coefficient is often be used for description flow resistance or relative roughness of a channel or floodplain. This research was focused on the effect of the height, density and arrangement of the artificial cubic roughness elements on Manning roughness coefficient. In total 48 experiments were conducted with three values of roughness height (5,10 and 15 mm), two percentages of roughness density (25% and 50%), two types of roughness arrangement (regular and staggered patterns), four flow discharge values on rough bed and four experiments with smooth bed in a laboratory flume. A length of 3.7 meter of the flum bed was designed as the rough bed according to the experiments plan. The results showed that the influence of the roughness arrangement on changing the value of Manning roughness coefficient (n) is more than the influence of the height and density of roughness. Also the mean value of Manning coefficient increased from 0.009 in smooth bed to 0.0132 in regular pattern and 0.0175 in staggered pattern. At last in order to compare with the results of previous works, some relationships have been offered in order to estimate the Darcy-weisbach coefficient (f) on the basis of the roughness density percentage at the bottom (C), relative submergence ( y ks ), Froude number of flow ( Fr ) and a factor related to roughness arrangement(€).

In recent years, using pedotransfer functions (PTFs) has been considerated as a way to estimate the hydraulic properties of soil from easily to measured parameters. In this research, soil water retention curve of a clay loam soil was estimated using some of the global and regional PTFs. Soil water retention curve (SWRC) was constructed using direct measuring methods in laboratory and the validation of PTFs for estimation of the mentioned curve was evaluated. By entering the measured and estimated SWRC to Hydrus-1D, soil water flow was simulated and the accuracy of the PTFs for simulation of water flow was quantitatively compared. The results showed that the functions of Sepaskhah (Sepas), Yaghubi-1(Y-(1)), Yaghubi-2(Y-(2)) and Ghorbani-2(Gh- 2)) with normalized root mean square error (NRMSE) values of less than 0.1 could reasonably predict SWRC of the surface soil. In prediction of SWRC of subsurface soil, the NRMSE values of most global PTFs were less than 0.3 and for most of the regional PTFs were less than 0.2. NRMSE values in simulation of water content of surface and subsurface soils using Hydrus by applying different PTFs were between 0.07 to 0.84, respectively. It can be concluded that in running validating phase one should consider the objective for which the PTFs may be applied.

Bridge failures due to scour at bridge abutments clarify importance of flow field around them. Scope of this study is the comparison between experimental results and numerical simulation of bed shear stress around bridge abutment in a compound channel by Flow-3D model. In order to calculate the experimental bed shear stress, flow velocity was measured by a 3D electromagnetic velocimeter in different levels of flow depth of floodplain. For estimation of Reynolds stresses of u w¢ ,u¢v¢ and v¢w¢ , in low flow depth of floodplain, extrapolations of these values to the bed were used. Experimental results showed that maximum bed shear stress occurred at the upstream corner of the abutment. After mesh generation, hydraulic simulation of flow with Flow-3D model was run in 5 turbulent models of Prandtl mixing-length model, one equation turbulent energy model, k-ɛ model, renormalized group (RNG) model and large eddy simulation model. Comparison between models showed that the results achieved by the RNG model had a better agreement with experimental observations and the pattern of shear stress around the bridge abutment was well predicted by this model. Bed shear stress at the upstream corner of the abutment was determined by experimental results and RNG model giving 3.84 and 4.6 N/m2, respectively.

In different regions of the world, numerous studies have been conducted on climate change. The results of those studies show the changes in climatic factors, especially in precipitation and temperature. Investigation of the precipitation phenomenon as one of the most important meteorological factors has a special importance in the availability of the water resources. In this study, using the precipitation concentration index in a seasonal scale, the variations of this important phenomenon in Iran, were investigated. Using the monthly rainfall time series data of 25 synoptic stations in Iran during 1961-2010, the precipitation concentration index values were extracted in the seasonal scale. The data were evaluated in two sub-intervals of 25 years. The significance of the mentioned index in two sub-intervals was analyzed using t-test. The seasonal trend of the precipitation time series and the precipitation concentration seasonal index were investigated using the Mann – Kendall test. The zonation results of precipitation concentration index showed that the distribution of the precipitation in the both sub-intervals obeyed the same pattern. The mentioned index in the south and central provinces of Iran having the low precipitation such as Kerman, Yazd, Sistan and Baluchistan had high values. In general, the results showed that according to the mentioned index, Iran's territory could be divided into three parts (from the view point of precipitation concentration pattern): the North area and Caspian Sea shores as the first part having the moderate density and pattern of rainfall, central as the second part having the irregular pattern of precipitation and the Oman Sea and the Persian Gulf margins having a highly irregular pattern of rainfall.

Sodium absorption ratio (SAR) and exchangeable sodium percentage (ESP) are two indicators of sodic soils. Several approximate correlations between ESP and SAR for soils of different regions in the world have been reported. The purpose of this study is to find the relationship between ESP and SAR in Miankangi region, in Sistan plain, and assessing possibility of ESP calculation from SAR. Thus, 189 soil samples from the study area were collected and analyzed. Relationship between ESP and SAR was determined by using the logarithmic regression equation of ESP = 8.07 × ln(SAR1:1) 10.20 and linear equation of ESP = 0.78 SAR1:1 15.69 (SAR1:1 is SAR in 1:1 soil to water extract), which could explained 83% and 67% of ESP variations respectively. Then, performances of multi-layer perceptron (MLP) network and artificial neuro-fuzzy inference system (ANFIS) were studied. Results showed the capability and better outcomes of MLP and ANFIS in comparison to regression models (correlation coefficient and root mean square error values were 0.94 and 0.05, respectively). These results demonstrated the superiority of intelligent models in explanation of the relationship between ESP and SAR compared with linear and nonlinear regression relations.

The purpose of this study was to determine the trend of agricultural drainage water salinity changes in outflow of the different spacings and depths, during the study time periods. In this research, an experimental box model was used with dimensions of 1.8×1×1.2 meters. The Drains at the depths of 20, 40 and 60 cm and spacings of 180, 90 and 60 cm, were installed in the box model and examined for the discharges of 0.14, 0.11 and 0.07 lit/sec. Groundwater and irrigation water salinities were chosen as 65 and 0.32 dS m-1, respectively. The results showed that in all drains the outflow water salinity was changed with time in a decreasing trend. With increasing the drains spacing, the amount of output water salinity increased and this increased the time to reach balance. The results showed that when the spacing, depth and discharge flow rate of drains were decreased, the effect of ground water on drain water was decreased.

Soil is a heterogeneous environment and its properties changes with space and time. Therefore, the investigation of spatial variation of soil properties is essential. This study aimed at investigating the spatial variation of soil parameters such as bulk density, salinity, lime percentage, and soil pH through application of different interpolation methods and choosing the most appropriate method for estimating the above parameters all over the plain. In order to apply geostatistical methods such as Kriging, co-Kriging and inverse distance weighting to determine the spatial variability of soil parameters, 301 soil samples were collected from the plain systematically and regularly, with the distance of 1500m between each two samples and then, soil samples were transferred to the laboratory. After that, the above-mentioned characteristics were measured. Using ArcGIS and GS softwares the variograms of these parameters were determined and the zoning maps for each parameter were drawn. Then, the data analysis was done in SPSS software. The criteria for evaluation of different geostatistical methods in this study was the mean and root mean square error by using cross validation technique. The results showed that squared inverse distance weighting method for bulk density and co-Kriging method for salinity, lime and soil pH had the lowest root mean square error and were the most accurate methods. Zoning maps showed a high percentage of clay in the soils of the northern part of the plain, which affect these soils salinity. In addition, the soil pH and amount of lime in Sistan’s soils were high so this region had calcareous and alkaline soils. bulk density has sharp, sudden changes in the region.

One of the common ways for bank protection against erosion along rivers’ bends is spur dike application. Spur dike changes the flow pattern and diverts it towards the river centerline and as aresult protect the river bank from erosion. However, a new flow pattern is formed with higher velocities and this phenomenon causes the local scour around the structure nose to be increased. The length of spur dike is one of the important parameters affecting the local scour around the structure. In order to investigate the effect of the permeable spur length (permeability was 33%) on local scour, experiments were conducted in a rectangular laboratory flume with a mild 90 degree bend (R/B=4; where R=radius and B=flume width). In this research a series of spur dikes with three different spur length including 10.5, 14.0 and 17.5 cm, corresponding to 0.15, 0.2 and 0.25 of flume width, respectively, was installed along the bend for each experiment. Four Froude number values including 0.21, 0.23, 0.26 and 0.28 with a constant flow depth of 14cm under clear water condition were applied for each spur length. The results show that the maximum scour depth increased with increasing the spur length for a constant Froude number; so that the maximum scour depth was happened for the length of 17.5cm with a Froude number of 0.28, which was 10.71% and 42.86% more than the spurs with 14.0m and 10.5cm length, respectively. The maximum local scour was observed to happen at the end part of the outer bank of the bend. It was generally found that with increasing Froude number and the spur length the scour hole dimensions increased.

Saline soils are one of the agricultural problems in many parts of the world. Soil salinity knowledge is an essential factor for proper land planning and management. Preparing soil salinity map based on fieldwork, especially in large areas, is time-consuming and costly. One of the useful technologies for soil salinity mapping is remote sensing for which various satellite data have been evaluated. In this study, potentiality of IRS-P6 images for soil salinity modeling in 180000 ha of Mahabad county lands was investigated. For this purpose, 147 soil samples from a depth of 0-15 cm using a systematic grid 1000 × 1000 meter were collected, and also the saturated electrical conductivity was measured. On the other hand, after the geometric correction of images, synthetic bands and salinity indices were generated. DNs of corresponding points in all bands and indices were extracted. After data normalization, correlation coefficient value between DNs and salinity was extracted. Band 2 and Fusion index (Pan and B2) had the highest correlation values of 0.73 and 0.736 respectively. The stepwise regression analysis was performed and a salinity model was developed with 0.628 correlation value. Finally, the model validation was performed using 20% of the samples, and the values of RMSE, ME and correlation coefficients between actual and estimated salinity values were obtained. The results indicated that IRS-P6 images could explain about 0.39 of soil salinity variation which reflect the high capability of the images in soil salinity modeling, according to the situation of the study area.

One of the most important factors of sustainable development of watersheds is qualitative and quantitative availability of suitable water resources. In this study, the artificial neural network (ANN), multi - variable linear regression (MLR), genetic programming (GP) and hybrid wavelet ANN (WANN) models were considered for modeling the monthly sodium absorption ratio (SAR) in Sefidrud River - Roudbar Station, and the effect of data preprocessing on model performance was investigated using the discrete wavelet Transform method. For this purpose, observed time series of river discharge and SAR were decomposed into several sub - time series at different scales by discrete wavelet transform. Then these sub - time series were introduced as inputs to the ANN model. The results showed that the hybrid wavelet - neural network model was more suitable for predicting maximum SAR values than the MLR, ANN, and GP models. Furthermore, the hybrid model could simulate the hysteresis phenomenon for SAR modeling rigorously, while multi linear regression method was incapable of detecting it.

In addition to decrease in useful lifetime of dams, the entrance of turbidity currents into reservoirs and their sedimentation near dam walls result in reduction of the useful volumof dam’s reservoirs, blockage of irrigation valves, and damages to the power plants. As a result, a large number of dams have been abandoned because of reservoirs sedimentation. One method thatcan control the turbidity current in to reservoirs is construction of obstacle. Using an obstacle can lead to the deviation or dissipation of the turbidity currents in reservoirs. In this paper, the effects of upstream angle of the obstacle as well as the water depth of reservoirs on controlling turbidity currents, were studied. For this means the Finite element method was employed using ANSYSY-CFX software. The results indicated that for subcritical and supercritical turbidity currents, as the level of water in reservoirs was declined, the efficiency of using an obstacle in controlling turbidity currents was decreased. Furthermore, when the upstream angle of the obstacle was increased, the obstacle was more capable of controlling the turbidity current.

Detection of discordant sites in a region is a very important issue in determining the homogeneous region which has the same statistical distribution. One of the powerful measures for this purpose is the discordancy measure in the L-moment approach. This measure, which is based on the mean and covariance of the data of all sites, sometimes cannot identify correctly the discordant sites. In order to improve this problem, the robust discordancy measure can be used based on the minimum covariance determinant estimator, which is less sensitive to outlying data. In order to analyze the regional frequency of droughts in the East Azarbaijan province, the classic and robust discordancy measures were utilized in this study. The results of two measures showed thsuperiorityof therobust discordancy measure against the classic one. In addition, after application of the cluster analysis and the heterogeneity measure, the study area was divided to three sub regions. Finally, the results of the goodness-of-fit measure revealed that the Pearson type 3 was the best regional distribution for all sub-regions.

Marand plain is one of the fertile plains of East Azarbaijan Province, in which due to the scarcity of surface waters, groundwater is the main resource for irrigation. In this study, multivariate statistical methods including correlation coefficient, factor analysis and cluster analysis were used to investigate the groundwater quality and origin of some heavy metals. For this purpose, 25 samples were collected from the existing groundwater resources and concentrations of some heavy metals, major ions and some species and minor ions (NO3 -, F- and SiO2) were measured. The results of cluster analysis put the water samples into two distinct groups. The first group is representative of fresh and deep groundwater and the second group is representative of saline and high hardness groundwater. Based on the correlation matrix, concentrations of metals such as Fe, Mn, Cr, Al, Ba and As are not highly correlated with major ions (Ca2, Mg2, K, Na, Cl , HCO3 - and SO4 2-) which represent entrance of these metals into groundwater through human activities. Cd and Pb have a relatively high correlation with major ions, which may indicate that the source of these metals is dissolution of rocks and formations. Factor analysis shows that variations in groundwater quality of the plain are influenced by three main factors including: 1- the effect of evaporate and salt formations, natural weathering of minerals and ion exchange process,
2- leakage from municipal wastewater and domestic absorption wells and agricultural fertilizers leaching and
3- weathering of potassium bearing silicates and application of agricultural fertilizers.

Usually, the impact of calcium and magnesium on improving and maintaining soil structure is assumed to be similar. This study was conducted to investigate the effect of different concentrations of magnesium on soil quality indicators. A clay loam soil was treated with fourconcentrations of magnesium (0, 1, 2, 3, 4, and 5 mmol/L) during 4 months in a completely randomized design with three replications. After this period, the mean weight diameter(MWD), wet aggregate stability(WAS) , clay dispersion (DS) and soil saturated hydraulic conductivity(KS )were measured. Analysis of variances showed that aggregate stability, hydraulic conductivity and clay dispersion significantly (p