مجله مهندسی و مدیریت آبخیز
سال پنجم شماره 2 (تابستان 1392)

Neka watershed is associated with a large number of floods from the past, and had irrecoverable damages. Land use and its changes is one of the most important factors in country planning and policy making. In this research, land use map of year 2000 was prepared for Neka watershed by ETM+ images of 2000 and IRS 1D images of 2011 based on digital processing of maximum probability in ENVI environment. Then, 2 km path upstream to Neka city was entered to GIS environment by 1:1000 scale plane maps and creating regional TIN and HEC-geo-RAS attachment. Finally, all data were imported to HEC-RAS software and flooding zonation was determined based on determination of roughness coefficient for two, three, five, 10, 20, 50, 100 and 200 return periods with Cown method. Results demonstrated that agricultural lands, Useless lands and municipal lands have been increased by 2.27, 7.31 and 1.91 percent, and forest and rangelands have been decreased by 10.22 and 1.27 percent respectively. These changes caused an increase of 13.14 percent of flooding zone in year 2011 compared to year 2000.

Prediction in hydrology is as estimation of hydrological and meteorological conditions in a specific interval time. In this regard, understanding the relationship between precipitation and runoff is necessary for water resources optimal management. The purpose of this study was to compare different models of artificial neural networks (two type of ANNs: RBF and MLP) and time series models (ARMA) to discharge estimation in a part of the Taleghan watershed, using monthly flow discharge data for a period of 30 years between 1977 and 2007. Among the different ARMA models, a model with a lowest error and akaike (AIC) criterion was selected as an optimal model. Using trial and error method, ANNs were designed by specifying the number of hidden layers and neurons in each layer, sigmoidal transfer function, training function, weight/bias learning function and performance function. Using trend analysis, Halt-Winters and Box-Jenkins (ARMA) methods, time series analysis showed that ARMA (2, 2) (R= 0.77) and Halt-Winters (R=0.72) presented more accurate results. In general, it could be concluded that ANNs models produced more accurate predictions of flow discharge than time series approaches. Also, the results revealed that the MLP model (average R=0.83) produced more accurate predictions of flow discharge than RBF model (average R=0.81). Assessment of accuracy of all models based on RMSE and R showed that the model 1 (with RMSE= 6.45 and R= 0.86) obtained with a network architecture of 4-20-1 configuration. Model 1 used the input vector consisting of antecedent monthly discharge with one to four time lag.

Base flow and related index is influenced by morphometric, geologic and hydroclimatological factors. As a result, it is precondition data for planning and water resources management. In this research, base flow and related index were extracted from daily stream flow data using one parameter recursive digital filter in eighteen hydrometric stations of the Caspian Basin. Physiographic, climatic, hydrological, and geological factors were calculated in GIS environment. Using factor analysis of the eighteen parameters, five factors were selected as independent factors. Statistical models were formulated to calculate several regressions between hydroclimatological and physiographic parameters. Further, residual analysis method was used to compare and evaluate the accuracy and efficiency of the models. Results showed that Hard Formations, the average height of basin, drainage density, and coverage of forest were the best predictors of the base flow index. Statistical models highlights importance of Q90/Q50 ratio as the suitable hydrologic index to estimate the base flow index. Besides, this model confirmed controlling role of Hard formations and the forest coverage on the base flow index.

Nowadays, application of remote sensing is common in soil conservation and erosion projects and most of them are used aerial photogarphs and desipte of the numerous advantages, there are some limitations. In this study, replacemen of moderate-resolution satellite data instead of aerial photographs has been investigated with emphasis on processing of satellite images and using image filters and the purpose of soil erosion figures detection. Finaly, image processing of area are prepared with maximum capability vitual interpretation of effects associated with erosion, after the study design, atmospheric and geometric corrections and perform pre-processing and initial processing on ETM+ and ASTER images. In order to evaluate the efficiency of filters for detection and identification of soil erosion were used low-pass and high-pass filters such as filters, median, mean, High Pass, Gaussian, Laplacian, Sobel and linear filters on ASTER and ETM images in the part of the Esfahan Dastkan basin. According to the results, using of low pass filters are not recommended because of the resolution reduction of soil erosion. High-Pass filters can be partialy appeard the edages of image and can be help to visual interpretation (especially in combination with the original image). Use of filters is recommended in combination with the image and as an aid to vitual interpretation, due to problems of application the fiters for separate soil erosion units. Regard to the dimension of soil erosion (rill and gully) and compared to the spatial resolution of the used sensor in this study, the erosions are not clearly appeared in the picture and application various image filters to automatically discover and exploit of these effects can not be efficiently. Resolution images of ASTER and ETM+ are not responsive for mapping erosion by using automated method and should be looked for a solution of semi-automated and visual interpretation. Also, because of the similarity between the spectral and geometrical picture was not found a major difference in the results. Therefore, it is recommended to produce a susceptibility map of erosion or erosion risk map instead the variouse types of regional soil erosion.

Soils containing rock fragments are covering major parts of land surfaces. Physical and chemical properties of soil are affected by rock fragments as they also affect on the hydrological and erosional processes. So far, many studies have shown the effect of surface rock fragments on soil erosion and runoff. Sediment production is a complex and ambiguous process and a notice to these effects is necessity. Hence this study examines the soil erosion reactions in different impermeable coverage of rocks with erosion plots and rainfall simulator. For this purpose, plots were covered with 0, 5, 10, 15, 20 and 25 percent of rocks, respectively. The results of sediment sampling and measuring the volume of runoff during 30 minutes of rainfall with an intensity of 70 mm/h were analyzed and the results showed that increasing of rock fragment coverage had no effect on runoff volume. But, the amount of sediment increased significantly (p<0/05) in soils containing rock fragments compared to soils without rock fragments. Although, results did not show a linear relationship between sediment values and rock fragment coverage percentage. The highest value of runoff and sediment concentrations observed in soils containing 10 and 20 percent of rock fragment coverage in comparison to other treatments. Finally, by increasing of surface rock fragments to 25 percent, the value of runoff and sediment decreased significantly. The results of this study confirmed the threshold levels in surface rock fragments to increase runoff and sediment values and also their dual roles at different levels.

Awareness of particle size distribution of river bed material plays an important role in studies of the organizing and analysis behavior of rivers. The traditional separation of particle sediments needs a lot of cost, time and fieldwork. Therefore, new methods such as image processing separation, is essential for studies on particle size distribution of riverbed sediments. It is necessary to maintain standards in reach to the goals and to justify the adoption of a new separation technique. Accordingly, the resolution of the camera is very important for standard image processing. However, it has not been considered, yet. Hence, the present study aimed to analyze the accuracy of the particle size distribution of bed sediments using the image processing of image taken by cameras with different resolutions. For this purpose, variety of cameras were applied to provide images with different resolutions. The direct samplings and measurement was also conducted for comparison purposes. The results showed that cameras with 3 and 10 megapixel resolutions had the highest and the lowest consistency with observed data with respective correlation coefficients of 0.65 and -0.51 for coarse sediment. The cameras with resolutions of 16 and 18 megapixel also had the highest and the lowest agreement with the observed data with correlation coefficients of 0.88 and 0.69 for fine-grained sediments, respectively. In principle, the results suggested that the most appropriate camera for image processing purposes born 10 to 16 megapixels of resolution. However, coarse-grained sediments ranged from 10 to 107 mm in diameter with the respective highest and the lowest standard deviation and mode of 98.455 and 89.7, and 21 and 14. The fine-grained sediments also ranged from 10 to 57 mm in diameter with the highest and the lowest standard deviation and mode of 33.143 and 17.10, and 12 and 48, respectively.Key words:

According to diversity and complexity of hydrological processes, more information and data for analysis of this aspect of drought, is needed. Hence, to achieve an index using observed data, simplicity and robustness, which is also capable analysis of this kind of drought, can be valuable. In this research, an index that includes both environmental and hydrological drought aspects was introduced. The foundation of the proposed method using flow duration curve as a method of analysis of hydrological drought and low flows is proposed. Performance of the desired Index (FDCI), with a proposed new Streamflow drought index (SDI) has been compared. To implement the method, three areas (Chalus, Joestan and Frizi river) with different aspects of size, climates and length of records, which are located in various regions of Iran, were selected. The results showed that the correlation between the proposed index and SDI (R2= 0.98, S.E=0.02) is highly significant. The superiority of the proposed method is the use of all available historical data without changing the original data. Hence, the application of FDCI for the analysis of hydrological droughts in rivers located in the Mediterranean and semi-arid regions should be consider as a main result of this research.

The purpose of this study is to test the efficiency of the Soil and Water Assessment Test (SWAT) and its applicability as a flow simulator, and using SWAT-Cup software and the SUFI2 algorithm as a means to calibrate and validate Tehran’s Latyan Dam upstream area. In order to test the efficiency of this model in simulating output discharge, by comparing Roodak hydrometric station simulation values situated at the exit of the area during an 11-year period (1997-2007), it was specified that the model did not perform well in simulating Bik discharges. Further on, at first, 21 effective flow parameters were entered into the SWAT-Cup software, which after analyzing sensitivity, 14 parameters were used for calibration and validation. Calibration was carried out for years 1997 to 2003, and validation was conducted for years 2007 to 2007. Different assessment indexes were employed to measure performance of the model in SWAT-Cup software and the SUFI2 algorithm, which indexes R2, NS, P-Factor, and R-Factor for the calibration period were 0.91, 0.88, 0.96, 1.79, and values for the validation period 0.92, 0.92, 0.9, and 1.54, respectively. Moreover, the Alpha coefficient for underground water, surface water delay coefficient, and soil outward density were recognized as the most sensitive parameters in output discharge.