Mohsen Bagheri Bodaghabadi; Mohammad Jamshidi; Zohreh Mosleh
Abstract
Soil organic carbon (OC) is one of the most important soil properties, especially from an environmental point of view. For this reason, OC modeling and estimating has been highly considered. In modeling, application of pedotransfer functions to estimate soil properties from the other ones have an important ...
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Soil organic carbon (OC) is one of the most important soil properties, especially from an environmental point of view. For this reason, OC modeling and estimating has been highly considered. In modeling, application of pedotransfer functions to estimate soil properties from the other ones have an important place in soil science. Unfortunately, not much attention has been paid to the valuable data that are obtained with the least cost and time in the soil profile description. The aim of this study was to determine the importance of data that obtained from soil profile description to estimate the soil organic carbon in Dehgolan region in Kordestan Province. For this purpose, 30 pedons were excavated and described. Soil samples were collected from different horizons and soil properties such as texture, pH, EC, CCE and gypsum were determined. Modeling was performed in three scenario including laboratory data, data of soil profile description and application of laboratory and soil profile description data simultaneously. The results showed that based on laboratory data, soil organic carbon has a significant relationship with silt and CCE properties with a coefficient of determination about 25% (R2 = 0.25); While, the two soil profile description data of soil color (chroma) and genetic horizon with coefficients of determination about 65% (R2 = 0.65). With compilation of laboratory and soil profile description data the coefficient of determination was also obtained 65%. This level of accuracy clearly shows the value and importance of data related to the soil profile description data.
Mohammad Tahmoures; davud nikkami
Abstract
Erosion and sedimentation phenomena are two inevitable phenomena of watersheds that are subject to complex factors. Identifying these factors and recognizing their effect on erosion and sediment will help in better planning to reduce the damage caused by erosion and sediment in a basin. In this study, ...
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Erosion and sedimentation phenomena are two inevitable phenomena of watersheds that are subject to complex factors. Identifying these factors and recognizing their effect on erosion and sediment will help in better planning to reduce the damage caused by erosion and sediment in a basin. In this study, to determine the factors affecting sedimentation, the Urmia Lake watershed was selected as the study basin. After identifying 30 characteristics affecting the sedimentation of sub-basins of the study area, including hydrological, physiographic, geomorphological, geological and soil characteristics, climate, land use and vegetation as independent variables, the amount of sediment produced in each sub-basin. Was identified as a dependent variable. Using factor analysis, principal component analysis (PCA), cluster analysis and stepwise multivariate regression between selected independent variables and dependent variable using SPSS software Statistical relationship was obtained between sedimentation of sub-basins and watershed characteristics. According to the selected regression model, it is determined that the amount of sediment in the watershed of Lake Urmia to five factors of agricultural land area (rainfed, irrigated and orchards), the area of sub-basins, the total area of erosion and Quaternary structures, average discharge The annual and basin form factor depends on the fact that these five factors control 89% of the sediment production changes in the selected sub-basins, which is significant at the 5% confidence level. In general, the factors affecting erosion and sedimentation of the Urmia Lake watershed can be divided into three groups: human factors and land use change, geology and physiography.
ghobad rostamizad; ali salageghe; ali akbar nazari samani; jamal ghodoosi
Abstract
One of the types of water erosion and land degradation which causes imbalance, is the gully erosion phenomenon. Land degradation, a broken ecological balance of the land and landscape and risk of falling at biological resources in these areas, the study of the gully, is inevitable and necessary especially ...
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One of the types of water erosion and land degradation which causes imbalance, is the gully erosion phenomenon. Land degradation, a broken ecological balance of the land and landscape and risk of falling at biological resources in these areas, the study of the gully, is inevitable and necessary especially in the Darrehshahr Township. In this regard, Gully 36 number were selected in Darrehshahr area in the ilam province. To this end, were identified environmental factors, Physical - Chemical Soil properties, cover and hydrological properties of gullies tested using aerial photography, the digital maps and field operations. To determine the extent effect these factors on each of the gully geometry characteristics using fuzzy logic and information theory, the membership function and the weights of the membership function of each of the factors was calculated. Then relationship between the independent and dependent variables was obtained by using multivariate regression. Results of statistical analysis using multiple regression (stepwise method) revealed that length of gully with upstream area of the gully, top and bottom width and cross section of the Gully with basin elongation, deep gully with basin elongation and slope curvature, high of head Gully with local slope of the gully and steep walls of gully with percentage cover have a significant relationship. So could be concluded that characteristics of geometry gully in the study area would be a function of the upstream, basin elongation, curvature slope, Local slope of the gully head and the percentage of canopy cover catchment area of gully.
Jamal Mosaffaie; Davoud Akhzari; Saeed Rashvand; Javad Ataei
Abstract
One of the important parameters in the design of flood control structures is to determine flood peak discharge for various return periods. A primary issue of planners in the face with flood is lack of data or insufficient data. One of the most reliable strategies is generalizing the results from sites ...
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One of the important parameters in the design of flood control structures is to determine flood peak discharge for various return periods. A primary issue of planners in the face with flood is lack of data or insufficient data. One of the most reliable strategies is generalizing the results from sites with observed data to ungauged locations. The main goal of this study is regional flood frequency analysis using multiple regression method for Qazvin province of Iran. 8 out of 23 existing hydrometric station were removed because of the short-term statistics and construction of storage dam at upstream. The results of factor analysis showed that perimeter, equivalent diameter, time of concentration, length of main waterway and area were the main variables affecting flood magnitude. The remaining 15 stations were divided into two homogenous regions using cluster analysis. Homogeneity of these two regions was confirmed using homogeneity and heterogeneity tests of L-moments. Based on the best-fit criteria of Zdist, GNO distribution with the statistic of 0.29 has the best fit for the entire region but for one and two homogeneous regions, GLO and GPA distributions with the statistics equal to 0.09 & 1.56 have the best fit respectively. After calculating parameter values for selected distributions, discharges with different return periods were estimated for all stations. Then, regression relations were obtained between peak discharge and factors affecting flood peak for each return periods at two homogeneous regions. Peak discharges at ungauged locations can be estimated for different recurrence interval using these relationships.
Ruollah Taghizadeh Mehrjardi; Fereydoon Sarmadian; Gholem Reza Savaghebi; Mahmoud Omid; Nourayer Toomanian; Mohammad Javad Rousta; Mohammad Hasan Rahimiyan
Abstract
In recent years, alternative methods have been used for estimation of soil salinity. Therefore, at present research, 600 soil samples collected from Ardakan in central Iran. Then EM38 and terrain parameters such as wetness index, land index and curvature as readily measured properties and soil salinity ...
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In recent years, alternative methods have been used for estimation of soil salinity. Therefore, at present research, 600 soil samples collected from Ardakan in central Iran. Then EM38 and terrain parameters such as wetness index, land index and curvature as readily measured properties and soil salinity (0-30 and 0-100) as predicted variables were measured. After that, the data set was divided into two subsets for calibration (80%) and testing (20%) of the models. For predicting of mentioned parameters, ANFIS, GA, ANNs and MLR were applied. In order to evaluate models, some evaluation parameters such as root mean square, average error, average standard error and coefficient of determination were used. Results showed that the ANFIS model gives better estimation than the other techniques for all characteristics whereas this model increased accuracy of predictions about 17 and 11% for EC30 and EC100 respectability. After ANFIS model, GA and ANN had better accuracy than multivariate regression.
v Payravand; ali Salajegheh; mohamad Mahdavi; mohamad ali Zare Chahouki
Volume 63, Issue 2 , September 2010, , Pages 131-18
Abstract
One of the most appropriate approaches for flood forecasting is using peak discharge data of hydrometric stations in each region. However, lack of such stations or short duration of data in most parts of the country, make it necessary to use some alternative methods in order to estimate the flood discharge ...
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One of the most appropriate approaches for flood forecasting is using peak discharge data of hydrometric stations in each region. However, lack of such stations or short duration of data in most parts of the country, make it necessary to use some alternative methods in order to estimate the flood discharge properly. One of these approaches is regional flood analysis method that in a region using observation discharge data in separate points, it calculates relevant regional flood models. These approaches give us possibility at a region without gauging station with similar and homogenous hydrological condition to estimate flood discharge for different return periods with acceptable accuracy. In this research three methods of regional flood analysis including index flood, multivariate regression and hybrid method were considered in 20 watersheds of central Alborz region. After taking into account, the hypothesis and limitations of each method, the results were compared with observed flood discharges using RMSE and MBE. Considering the hypothesis and validation of multiple regression model indicated it is not appropriate. Finally Index Flood method in return periods of 2, 5 and 10 years and hybrid method in return periods of 50 and 100 years proved higher accuracy in the whole region and no difference between these two methods in return period of 25 were shown.
