Salman Mirzaee; Shoja Ghorbani Dashtaki; Jahangard Mohammadi; Hossein Asadi; Farokh Asadzadeh
Abstract
Understanding the spatial distribution and variability of erodibility and soil properties is essential for planning of water conservation methods, controlling of flood and runoff and managing of soil erosion or watershed. Selecting and using appropriate interpolation techniques for soil properties and ...
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Understanding the spatial distribution and variability of erodibility and soil properties is essential for planning of water conservation methods, controlling of flood and runoff and managing of soil erosion or watershed. Selecting and using appropriate interpolation techniques for soil properties and erodibility mapping by erosion models such as WEPP is essential. The objective of this study was regionalization of interrill erodibility and effective factors like clay, organic matter and lime using kriging and cokriging and remote sensing data (Landsat 7). For this purpose, 100 soil samples were selected randomly from 0-15 cm depth of Selin watershed in Kaleibar region of East Azerbaijan. Interrill erodibility of WEPP model and some soil properties as clay, organic matter and lime were measured. Correlation analysis between soil properties and digital number (DN) ETM+ image showed that clay, organic matter, lime and interrill erodibility had the highest correlation with DN of Band 7, 1, 1 and 3 ETM+ image (−0.406, -0.431, 0.291 and 0.299), respectively. Therefore, the DN of these bands used as auxiliary data for cokriging estimator. The spherical model was fitted the best model to calculate variogram of interrill erodibility, clay, organic matter and lime. No significant difference were noted between kriging and cokriging despite using remote sensing data as auxiliary data. This can be attributed no strong correlation between interrill erodibility, clay, organic matter and lime and remote sensing data.
Banafsheh Yasrebi; Majid Soufi; Sayed Khalagh Mirnia; Jahangard Mohamadi
Abstract
Gully erosion has an important role in land degradation producing much sediment. Due to development of gully erosion in crop lands of study area, this research deals with assessing the topographic characteristics of bank gullies and assess on effective soil factors controlling gullies advancement in ...
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Gully erosion has an important role in land degradation producing much sediment. Due to development of gully erosion in crop lands of study area, this research deals with assessing the topographic characteristics of bank gullies and assess on effective soil factors controlling gullies advancement in Siekan watershed in Ilam province. For this purpose, 46 bank gullies were selected and morphometric characteristics like initial and advancement contributing area and slope as well were measured. Two compound soil samples were collected from top soil of contributing area and gullies walls then analyzed in the soil lab. Then database formed and effective factors on gullies advancement were recognized by correlation matrix and regression.Correlation matrix results revealed, the higher slope the higher head-cut and gullies volume. A-S relationship is negative and b is 0.31 that shows gullies formed by hortonian overland flow process. Topographic threshold is 0.04 and mean threshold in 10% slope is 0.05 ha and in 2% slope is 2 ha. Critical threshold in 2% slope is 0.07 ha. Correlation matrix showed that increase in gully advancement slope increases head–cut height and gully volume. The index of area of development/ area of initiation is suitablefor gully development stage determination and it has negative relationship with gully length, volume and width/depth index. Increasing in soil organic matter cause an increase in topographical threshold, soil texture and electrical conductivity increase the gully volume. The effect of both topographical parameters and soil material characteristics on total eroded bank gully volume was integrated in multiple regression equations. The models based on all measured parameters explain 85% of the variation ingullies volume.
