پژوهشنامه مدیریت حوزه آبخیز
پیاپی 13 (بهار و تابستان 1395)

The present research was conducted with the purpose of assessing the interaction between some soil properties and runoff generation time in the downstream of Educational and Research Forest Watershed of Tarbiat Modares University (Kojoor Watershed) located at Southeastern of Nowshahr. Rainfall simulation was done through applying a pumping rain simulator generating rain intensity of some 1.6 mm min-1. Accordingly, runoff generation time was determined from starting time of the simulation until runoff generation. In this research, some soil characteristics such as percentages of organic matter, clay, Silt, sand, antecedent soil moisture contents and soil bulk density were analyzed at two topography characteristics of slope steepness and aspect. For statistical analysis, a normality and variance homogeneity test was firstly carried out and variance analysis was then adopted. The significant relationships were ultimately evaluated using the Pearson correlation test. Results showed that the soil properties were strongly correlated to each others. Amongst them, there were just a positive correlation between the percentage of organic matter and topography properties with runoff generation time in the significant level of 5 %. Most of the runoff generation time were measured from plots of 44% and located at the western aspect that had the highest percentage of organic matter of 5.9%. It could be inferred from the results that the runoff generation time was significantly sensitive to environmental variables.

Climate change has a critical impact on water resources, especially in arid regions. In the first part of the study, the LARS-WG was used for downscaling of climatic variables including rainfall, solar radiation, minimum and maximum temperature over the Ghareh-Chay basin in Markazi province for a 31 year historical period (1983-2013). Results showed that LARS-WG can be applied successfully to downscale the climatic variables. By using the three emission scenarios, A1B, A2 and B1 in different future horizon, decreasing and increasing trends were seen for rainfall and temperature, respectively. In the second part of study, adaptive inference neuro fuzzy system (ANFIS) was applied for run-off simulation over the basin for three different horizons, 1400, 1435 and 1470. Two different identification methods namely, grid partitioning and subtractive clustering were used for ANFIS model. Performance of the subtractive clustering was slightly better than the grid partitioning in run-off modeling process. The results indicated that in comparison to the baseline period, the maximum discharge will be reduced by14, 27 and 43 percent in 2020, 2055and 2090 horizons, respectively. Based on the occurrence of climate change over the basin and intensification during the next years, it seems necessary to consider some ways for adaptation and coping with climate change for protecting the water resources.

The land use change is one of the major challenges of the human communities in this century and even more its impacts are than the climate change phenomenon. Land use change influences run-off as well as the other hydrologic factors such as interception, infiltration and the flood intensity. This study is aimed to investigate the impact of last 30 years of land use changes on hydrological behavior in the Kasilian watershed. Satellite data of Land sat MSS, ETM and IRS LISSIII were used to detect land use change for the years of 1977, 2001 and 2007 respectively. The extracted results from this period a declination trend in the forest cover which was the cause of the increase in the runoffs identified in HEC-HMS used model. After calibration and validation of the used model for the indicated timescales, it shows that the deforestation impacts was increased the peak discharge to 2.11 m3 and also the run-off volume to 98.81 m3.

The process of infiltration is one of the most important components of the hydrological cycle. On the other hand, the direct measurement of infiltration process is difficult, time spending and expensive. Infiltration models play a main role in managing water resources. Therefore, different types of models with various degrees of complexity were developed to reach this aim. So, this research carried out to the determination of the best infiltration estimation model in Rangeland, forest, agriculture land uses, in the Kakasharaf Watershed in Lorestan province. In this study, infiltration measurements were carried out using the infiltrometer double rings and Philip, Horton, Green-Ampt, Kostiakov and Soil Conservation Service of America (SCS) models, and use to estimate the infiltration. The results of this study showed that in rangeland use, the infiltration of all parameters (cumulative infiltration, the final infiltration rate, infiltration rate and the average time until stabilizing infiltration), is less than forestry and agriculture land use. It also compares the models, in the rangeland, Soil Conservation Service Model, with Nash-Sutcliffe efficiency coefficient 0.910 and coefficient of 0.915, and in land use of forest and agriculture, Philip Model with Nash efficiency coefficient, respectively 0.850 and 0.784, were selected as the best models in the three land uses. The Horton model was selected the weakest model in all of the three land uses as well.

One of the challenges for hydrologists is finding a new method for hydrologic classification of catchments. An appropriate classification method can be effective in many branches of hydrologic science like modeling. To deal with the complexity and nonlinearity of hydrologic processes, some researchers have proposed using the chaos theory for catchment classification. In this research, possibility of using this concept in classification of 60 catchments in Iran (using daily runoff data) has been analyzed and embedding dimension (M) of dynamic systems has been used as a parameter for catchments classification. Regarding the obtained results, catchments can be classified into three group whit high (probability), average (deterministic-probability) and low (deterministic). The results indicate that although there is some similarity and homogeneity in some regions and climates, using the geographic position of a catchment can’t suggest a group that the catchment belongs to and that, insteade embedding dimension can be used as a criterion for catchment classification.

Simulation of stream flow, prediction of the hydrological behavior of watersheds and understanding of various components of the hydrological cycle is important in order to plan for protection of water resources. On the other hand, lack of proper estimation of runoff in the watersheds, may cause serious problems in the optimum management of water resources and particularly the utilization of dams and water transfer systems. The main objectives of present study were application and test the performance of Soil and Water Assessment Tool (SWAT) as a simulator of monthly stream flow in the Ghareh Su watershed with an area of 4062 km2. The simulation was carried out using flow data from the Samian, Pol Almas and Yamchi hydrometric stations for 8-hydrological years (from January 2003 to December 2010), where data for the six years (from January 2003 to December 2008) were used as a calibration period and validation period was done for two years (from January 2009 to December 2010). The performance of the model was evaluated by coefficient of determination ( ) and Nash–Sutcliffe efficiency ( ). The values in Yamchi, Samian and Pol Almas hydrometric stations during the calibration and validation periods were 0.70, 0.68, 0.34 and 0.82, 0.53, 0.63, respectively. The values were 0.51, 0.58, 0.09 and 0.51, -0.33, 0.60, respectively. The statistical analysis showed a satis factory agreement between observed and simulated monthly discharge values, in Yamchi hydrometric station during the calibration and validation periods. The weakness of the model to simulate flow for some months was probably due to a poor characterization of snowmelt processes, the discordance between model assumptions with flow transmission in frozen and saturated layers, lack of sufficient discharge data, and lack of input data for simulation of groundwater recharge and groundwater-river interaction.

Quantifying the effects of watershed management projects is a first step in the evaluation of their efficiency. Selecting suitable index for evaluation is an important concern in an evaluation process and is determined on the basis of project type, evaluation method, required accuracy, and available data. Watershed management projects have been initiated in Goosh-Bahreh Watershed, Khorasan Razavi province, since 1993. Considering the importance of watershed management projects evaluation, peak flood discharge and flow volume were adopted as suitable indices. Field surveys and available recorded documents were used to provide required data and information on locations and specifications of the projects which are built on the main streams. To quantify the effects of the projects, river flow was simulated by using HEC-HMS model. The results showed that biological and mechanical projects lead to a decrease of 36.21% and 34.78% in peak discharge and flood volume at different return periods, respectively and the effect of watershed management projects on the peak discharge and flood volume decreases as return period increases. This research showed positive effects of watershed management projects on flood discharge and flood volume in the Goosh-Bahreh Watershed.

The spatially distributed hydrologic model WetSpa is applied to the Dinvar river basin (1717 km2) located in upstream of the Karkheh Dam. Daily hydrometeorological data from 1382 to 1389, including precipitation data from 9 stations, temperature and evaporation data measured at 4 stations are used as input to the model. The spatial characteristic of the basin is described by three base maps, i.e. DEM, land use and soil type, in GIS form using 100 m cell size. Results of the simulations show a good agreement between calculated and measured hydrographs at the outlet of the basin. The model predicts the daily discharge values with a good accuracy, i.e. about 66% according to the Nash-Sutcliff criterion. Sensitivity and uncertainty analysis of the model parameters is performed using a model-independent parameter estimator, PEST. It is found that the correction factor for calculating the groundwater flow recession coefficient has the highest relative sensitivity and the parameters kss and kep located in two and three ranks of the relative sensitivity. Parameter uncertainty analysis shows that parameters ki; kep, kss and kg have high certainty and as well as parameters krain, kmax have low certainty.

Knowledge of river discharge and water-quality trend can be useful for planning and management of water resources. Due to the fact that the river base flow is supplied by ground water, considering of base flow for managing environmental demand. The Mann-Kendall's test is one of the approaches which is used for investigating of the trend in time series. In this study, the Mann-Kendall's test was used. For separating the base flow from daily discharge data, Hydro Office software was used. Then, after separating the base flow, monthly and annual time series have been formed. Also, the monthly and annual time series of water-quality characteristics including TDS, Ca, Mg, Na, SO4, CL, EC, PH, HCO3 and SAR of Arazkoose hydrometric station were formed to assess the trend of total flow, base flow and Water-quality characteristics data. Meaningful analysis of trend at the significant level of %5 indicates that, there is not any trend in total flow, base flow and Water-quality characteristics except PH in annual time scale. The result also shows that there is a fluctuating trend in monthly time scale.

Simulation of rainfall-runoff process is a major step in water engineering studies and water resources management. In this study, the rainfall-runoff process of the Siminehroud monthly (1377-1390) were simulated using Support Vector Machines (SVM) with Radial Basis kernel Function, Polynomial and linear Bayesian Network (BN) with a PC Learning Algorithm, also conventional methods such as Artificial Neural Networks (ANNs) and Gene Expression Programming (GEP) were used; finally, the results were compared with each other. Correlation Coefficient (CC), Root Mean Square Error (RMSE) and Nash-Sutcliff coefficient (NS) were used to evaluate the performance of the models. The results indicate the acceptable performance of the models and GEP model shows the highest CC (CC = 0.91), minimum RMSE (RMSE = 1.3 m3/s) and NS = 0.82 in verification stage.

Groundwater level prediction is an important issue in scheduling and managing water resources. A number of approaches such as stochastic, fuzzy networks and artificial neural network have been used for such prediction. A neural network model has been employed in this research for Shahrood plain groundwater level prediction. For this reason, statistical parameters of groundwater level fluctuations for 16 successive years 1994 to 2010, have been used and also, weather forecasting parameters for 16 successive years from 1994 to 2010 have used. This study indicates that some of the data are correlated an possesed a seasonal pattern. This issue makes difficult the forecasting process. Hence, the proposed method employed policies for non season analyzing, normalizing, and ignoring the correlated date. 85% of the data for train and the rest for testing the proposed neural networks model have used. Results indicate that the proposed method can predict groundwater level of Shahrood Plain for three successive years with the mean square errors of 0.0257m, 0.0270m and 0.0452m. Also, the prediction shows that if the precipitation decreases 30 percent in a year, the groundwater level will decrease 0.7 m.

Due to the extent of Iran and the variety of climates in different area with variation of precipitation cause urgency obtaining to new methods for flood calculations. For this purpose necessary, efficient of new method assessment in compare of current method in different area of Iran until if suitable fitness for different region, used to calculation of flood. Two current methods for calculating of statistical parameter about flood have been ordinary moments and maximum likelihood that these methods calculate in Hyfa (Hydrological frequency analysis) and using of these results in our country. Another new method for computation of these statistical parameters in the recent years, that using in the world have been linear moments that applied by Hydrological experts for assessment in different area of the world and have been suitable recommendation for applying of this new method. The aim of this research was assessment of efficiency of this method in the selection area of sheikh Osman watershed from Oshnavieh in west Azerbaijan province as has been assessment, efficiency of this method in this region and if suitable developed for another region of Iran. The result of this study distinguished for five selection station in this region and pay attention to comparison between three methods of ordinary moment ,maximum likelihood and linear moment method, the best selection method and distribution have been the Gamble distribution with linear moment and extinct efficiency of this method for calculation of annual maximum peak floods that distinguish more accuracy compare with current method.

Rainfall runoff modeling and prediction of river discharge is one of the important practices in flood control and management, hydraulic structure design and drought management. The present article aims to simulate daily streamflow in Kasilian watershed using an artificial neural network (ANN) and neuro-fuzzy inference system (ANFIS). The intelligent methods have the high potential for determining the relationship between inputs and output. In this study, the input parameters are rainfall, evaporation and temperature of Sangdeh station and streamflow data of Valikbon station are selected as output during 2003 to 2009. The partial auto-correlation function (PACF) was employed for selecting appropriate input parameters to the ANN and ANFIS models. Among different variables in both models, rainfall and evaporation with 1-day lag time were selected as optimal parameters. Then, the results were evaluated using RMSE, NSH, MAE and Rmod statistical criteria for presenting optimal model. The results showed that ANFIS with bell-shaped function and radius of influence=0.14 and NSH=0.80, RMSE=0.056, MAE=0.11, Rmod=0.81 statistical criteria were found to be superior to the ANN with the similar structure, the Levenberg-Marquardt training algorithm, sigmoid transfer function, 14 neurons in the hidden layer and NSH=0.54, RMSE=0.056, MAE=0.14, Rmod=0.87 in testing stage for rainfall-runoff modeling in Kasilian watershed.

Although a small portion of the Earth's surface is covered by the mountains, but it has a large impact on watershed hydrological perspective Because of the water crisis in arid and semi-arid regions of Iran, monitoring of the amount of snow in these areas is very important. Usually, access to the spatial distribution of snow water equivalent is limited to small scale using sampled data. However, due to the limitations of the mountainous, snow sampling of area is difficult and sometimes impossible in the large basins. Thus, the development of methods in order to estimate snow water equivalent at the un-sampled locations is essential. In this research, an area of 16 ha area in Yazd province was selected and snow water equivalent was measured at 216 points using a Mt. Rose snow sampler. Then the application of artificial neural network method was evaluated using 31 geomorphometric parameters and the digital map of snow water equivalent was obtained. The results showed that the artificial neural network can estimate the snow water equivalent by a R2=0.83 and RMSE= 3.55.The results of the sensitivity analysis are also showed that among the ANN parameters used in the prediction of snow water equivalent, Plan Curvature, Profile Curvature, Curvature, Wind Effect, Slope, Multiresolution ridge top flatness index (MRRTF), Catchment slope and Multi resolution index of valley bottom flatness (MRIVBF) are the effective parameters to predict snow water equivalent, respectively.

Main part of Iran is in arid and semi-arid region and water is a limiting factor of human activities in this area. One of the ways to overcome seasonal shortages of water is using groundwater. Underground dam is a storage methods and use of groundwater that it can be used to improve water resources management and increase utilities of these resources. In this study, It has been tried to identify the most effective locations for the construction of underground dams in the watershed of Alashtar by combing GIS and multi criteria decision systems. For this purpose, were prepared data of 8 affecting parameters were prepared slope, geology, land use, geomorphology units, faults, streams, wells and residential areas in studied area by GIS. Weight of each criterion and weight classes of each layer was calculated by ANP method and paired comparison in Super Decision software. In next stage, restricted areas were removed. Then each of the defined criteria was classified for area using the GIS analytical functions. At the end, the final map was prepared in five classes from very good to poor by combination of zoning maps based on the weight of the ANP method. Results indicated that 15% of the study area is very suitable, 11% suitable, %18 elatively suitable, %37 unsuitable and %19 relatively unsuitable.

Management of underground resources has a special priority in arid and semi-arid in Iran. Increasing underground resources is one of the useful ways for providing water requirements during the drought years. The main objective of this study was for mapping underground dam in the arid and semi-arid area in western Iran. The first and important stage of underground dam construction is recognizing an appropriate location of dam. In this research, after investigating the previous study and improving some basic information, different layers were integrated using GIS technology to determine the location which has a potential for these structures in the study area. These layers were including fault, slope, geology, geomorphology, rainfall, temperature and land use. The IRS satellite imagery in 2007 was used for providing the geomorphology map and land use map as well as well to determine the correct location of dams. Then, a number of 14 appropriate locations were selected using field data collection and the AHP method for constructing the underground dams in the study area.

In this study, management plan was developed for normal and critical scenarios in the
Chehel-Chai watershed. Landslide distribution map of the study area was created using air photos interoperation and field studies. Landslide management plan also was suggested for five management strategies: without management program, low-risk tolerance, zero risk tolerance, avoiding of risk and controlling measures. The management plan was developed for both normal and critical scenarios. Additionally, multi-criteria evaluation was used to calculate the management score. Results show that in the two normal and critical scenarios, 6.67% and 11.8% of the Chehel-chai watershed need controlling measures, respectively. In contrast, 37% and 12.57% of the study area are identified as the areas that do not need any intervention (without management program), with respect to the two scenarios respectively. The kappa index of agreement for the management plan maps corresponding to both scenarios was calculated as 0.64 suggesting that there is 36% difference between the two management plan scenario maps. The implementation of the landslide management plans based on this research in local and regional scales can solve the problems arising from hill slope instability. This can lead to appropriate watershed management practices and therefore to achieve sustainable development.

The Occurrence of more than 400 landslides in Chaharmahal and Bakhtiari province shows a special sensitivity against erosion in this terrain. To investgate the role of the soil physical, chemical and mineral properties on the occurrence of the landslides in Afsar-Abad, Do ab Samsami in the west of Chaharmahal and Bakhtiari, were drilled six boreholes in sliding boundary and safe restrictions on the quaternary Slope Colluvium. The sampling has done in three depths after profiles analysis. Physical properties such as bulk density, true specific gravity, saturation percent and soil texture along with chemical characteristics including organic matters, limestone, gypsum, dissolve cations were measured. The soil texture is silty clay loam in both experiment groups. The results are analyzed and interpreted through statistical methods. They show that there is a meaningful difference in the amounts of clay, organics, Silt, Ca, Mg, and EC of both control and experiment group. Silt has a direct relationship with landslide occurrence. Piping occurs due to the increase in the underground water level and subsurface erosion; consequently silt is washed away from the body of the soil. The increase of clay in the safe area can prevent earth-sliding. Thus, low or average amounts of clay in the soil lead to the stability of both soil structure and soil particles. This, in itself, prevents soil collapse. The amount of Ca has a reverse relationship with landslide. This shows the important role of this cation in increasing the stability of the soil structure, as well as the shear strength, and finally the earth stability against any rupture in the soil particles. The increase in the amount of EC in the sliding areas points out the effect of the dissolution of salts as Nacl and Kcl which is itself caused by the increase of the amounts of rainfall (about 900 ml a year) and consequently the increase of the underground water level. Thus, landslide could be prevented by chemical remediation.

Studies related to erosion and soil conservation of litho logical and geological characteristics of catchments have particular importance, Due to their effects. Erosion and sediment production are related to many factors, in which, the sensitivity of geological formation to erosion is the most important parameter. In this study, formations sensitivity to erosion in two sub-basins of Doviraj River located in Ilam Province is compared and their role in erosion and sediment yield has been investigated. In order to study the sensitivity of geological formations the Faiznia (1996) method is used. Results showed that the erodibility of the geological formations has a significant role in the erosion and sediment production, so that, the erosion and sediment yield of the first catchment is 2.5 times as much as the second catchment, because 92.4%of the sub-basin 1, is classified as sensitive to erosion and 7.45% the average class of sensitivity, but in the sub-basin 2, the above amounts are 65.01% and 34.99% respectively. Also, in the sub-basin 1, the Gachsaran formation which covers 6304 hectares (82.09% of the catchment) has the highest frequency and the above figure in the sub-basin 2, is 2166.86 hectares (49.07% of the catchment). Higher erosion and sediment yield of the sub-basin 1 compared to the sub-basin 2 is due to the existence of sensitive formation to erosion, especially Gachsaran formation which has the highest frequency in the study area.

Watersheds are changed positively or negatively as biotic and abiotic factors in natural circumstances impact them. Landslides, as a physical factor, one of the negative consequences on these catchments. Masoleh watershed, in North of Iran, is one of the susceptible areas to explode the natural landslides. In other to landslide hazard zonation, the Dempster-Shafer model is which is used has 14 effective factors including, geology, slope, slope aspect, altitude, distance from faults, distance from road, distance from stream, distance from the fold, Stream Power Index, Compound Topographic Index, Rangeland condition, soil texture, rainfall and land use. Results showed that geology formation and distance from the fold factors have a consequential role to construct the lands life hazard in this area. Overgrazing, grazing in forth off-season, early grazing, late term departure of animal from rangeland and surplus livestock are considered as direct affecting factors on vegetation condition have simultaneous role to make the landslide hazard. From the other point of view, results showed that there was a close relationship between landslides and rainfall. So that parts of the study area which have the bare ground, high stocking rates, maximum rainfall; numerous landslides have occurred. Evaluation result of Dempster-Shafer model using ROC method has a superior accurate to evaluate the landslide risk in the study area. Therefore, regarding the affecting factors of the landslide hazard and knowing that status in each region, as an influence tool, has important role to exhaustive management of the watershed.

Accurate estimation of sediment load in rivers and reservoirs is an important issue in hydraulic engineering as it affects the design, management and operation of water resources projects. Extract of mathematical relationship in sediment transportation has special complexity. Data-driven methods can be used for Modeling of these phenomena. One of these heuristic self organization methods is Group Method of Data Handling (GMDH) that is uses as a method to detect non-linear relationships between input and output variables. In this research, based on GMDH, a model has been developed for the prediction of suspended sediment concentration in river systems. The daily stream flow and suspended sediment concentration data from two stations, Rio Valencia no Station and Quebrada Blanca Station, were used for evaluating the ability of model. The accuracy of model was evaluated using mean square error (MSE), Relative Bias (RB) and determination coefficient (R2) statistics. Comparison between the results of statistical parameters of model with other algorithms like Neural Networks, Neuro-Fuzzy and Genetic Programming indicated that GMDH has high capability for predicting and simulating of suspended sediment concentration than other models.

Due to global warming, and its resulting changes in the frequency and amount of precipitation and temperature, there has been a great concern on climate change impacts by the scientific community. This study focuses on trend analysis of annual and seasonal rainfall (P), maximum temperature (Tmax) and minimum temperature (Tmin) time series from seven meteorological stations in Gorgranrood river basin during 1982-2011. Three statistical tests including, Mann-Kendall (MK), the Modified Mann-Kendall (MMK) test and Man Wintney (MW) were examined at 10% significance level. To quantify the slope we used Sen’s non-parametric estimator of slope. Both positive and negative trends were identified by all the tests. However, all negative trends were insignificant and only some positive trends were significant. Trend tests reveal that the median of slopes of seasonal series of Tmax, Tmin and P are located above zero line which is revealed that increasing trend is observed in most of the station Steepest positive slope of trend line of the Tmax is found in the spring then in summer time. Trend analysis has revealed strong seasonal variability of Tmin series. The highest number of stations with significant trends occurred in the Tmin while less significant trends were detected in the Tmax and P. There is a non-significant increasing rainfall trend in the basin. With regard to seasonality P, it is remarkable that positive significant trends were detected in few stations at both annual and seasonally time scale. In order to remove serial correlation, the trend-free pre-whitening procedure has been applied and less number of positive trends has been again observed, highlighting that, in this case, serial correlation affect the results of Mann-Kendall trend test.

In this study, the influencing factors on farmer's participation in use of soil and water conservation practices were investigated using the farmer's experiences in Shahroud river basin. For achieving this goal was used from multinomial logit model. The required dates are related to year 2011-2012 that by completing the questionnaire from 138 sample farmers were collected. To select the sample farmers were used of stratified random sampling method and Cochrane formula. The results showed that only 42/7 percent of farmers in Shahroud river basin employ conservation practices moderately. Logit regression model results showed that education, slope of lands, knowledge of conservation practices, the annual gross income, receiving of grants, participation in promotional classes have positive and significant effects and age and employment in non-agricultural sector have negative and meaningful effects on the probability of farmer's participation in use of soil and water conservation practices. Multinomial logit model in high confidence level by likelihood ratio test statistics with 30/57 for mechanical practices, 19/68 for non-mechanical practices and 24/32 for management practices was significant. The maximum probability value is equal to 0/065 and for non-mechanical practices was obtained.

One of non-forage functions of rangelands vegetation is soil conservation and prevents it from erosion. Water soil erosion has economic, social and environmental implication due to both on-site and off-site effects. So, the objective of this study was to assess the on-site effect of water erosion on conservation function of summer rangelands vegetation, using a combination between economic value and various vegetation density of Baladein North of Iran. So, economic value of soil conservation estimated by "loss of forage productivity" method. The initial framework of the model was bio-economical. The model fitted by Cobb-Douglas production function by OLS method. This function is based on soil physic-chemical parameters and soil erosion ratio. Results showed that only soil erosion had significant effect on forage production. According to the marginal production (MP) and economic value of each kg of soil conservation, value of MP (VMP) estimated per ha by different plant vegetation density. The results showed that, economic value of loss of forage productivity estimated 230084 Rails/ha from 94978.6 ha of rangelands. The most soil conservation value wasbelongedto rangeland with high density by 10.86 milliard Rails and the least value was belonged to rangeland with low density by 1.31 milliard Rails. Results showed that similar research in natural resources filed by natural vegetation is required to consider other independent variables in the initial framework of the function.

Severe lack of data on soil erosion and sedimentation in many national watersheds requires the application of appropriate empirical methods for their estimation. This study is aimed to evaluate the efficiencies of Universal Soil Loss Equation (USLE) and some of its variations including MUSLT, MUSLE-E, MUSLE-S and AUSLE in semi-arid climates. This study was undertaken on standard plots in the ranges of Margsar, range and livestock management research station, Jashlobar, Mahdishahr, Semnan province. For this, all of required variables and input data for the respective models have been calculated for the respective plots. Finally, the estimations from both models and measured sediments have been compared during 15 showers. The results of t student’s t-test showed that there is no significant difference between MUSLE-E, MUSLT and MUSLE-S models and the measured sediment. Also, the results from efficiencies of the models by Nash-Sutcliffe method as well as relative root mean square error (RRMSE) showed that MUSLE-E, MUSLT and MUSLE-S models have higher efficiencies than other variations.

Rivers have different patterns of plan forms. Straight and meandering rivers have single channel but braided, anabranching and anastomosing rivers have multi channels. Gamasiab River in Kermanshah province has different plan forms of channels. In this study, historical method is used and is investigated different plan form and river's changes with using of aerial photography of 1955, 1969, 2003 and IRS satellite imagery 2010. Aerial photographs are ortho photo in Arc Map software based on 1:25000 topographic maps. Channels and bars were digitized and river is divided to 12 reaches. Braided index and sinuosity for different reaches were calculated. Results show that river channels have remarkable changes during the past 56 years. Evolution occurrence on the upstream section has changed from meandering to anabranching. Channel avulsion is defined as the rapid lateral relocation of a river course across parts of its floodplain due to formation of new channel and makes a condition for creating an branching plan form. In the intermediate reach of stream section changes from meandering to braided river. But in the downstream reaches section have a meandering plan form and these reaches do not have changes in the plan form during in the past 56 years.