Nadegholi Ebrahimi; Aliakbar Davudirad
Abstract
In order to investigate of geological formation effects on sediment yield in Gharah Kahriz watershed at first by overlaying the base maps such as land type, geology, slope and vegetation, the unit land map were obtained. The amount of sediment yield calculated using MUSLE model in each homogen unit. ...
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In order to investigate of geological formation effects on sediment yield in Gharah Kahriz watershed at first by overlaying the base maps such as land type, geology, slope and vegetation, the unit land map were obtained. The amount of sediment yield calculated using MUSLE model in each homogen unit. In order to achieve the objectives of the study, units that was widespread in the region and were almost homogenous in land use, slope and vegetation and the only difference was the type of geological formation, were selected. The results show that the maximum amount of sediment yield during flood events were observed in Kmml unit that contains layers of limestone and marl with average of 13.34 t.ha-1, and the minimum amount of sediment yield belongs to the Js unit that compound of Jurassic sandstone with average of 0.20 t.ha-1.
Heshmatolah Agharazi; Aliakbar Davudirad; Mahdi Mardian; Majid Soufi
Abstract
Recognition of effective processes of erosion, especially, threshold is one of the most important strategies in water and soil resources management. Gully erosion is one of the most important sources of sediment yield in watersheds that is defined as different thresholds like area-slope or topography. ...
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Recognition of effective processes of erosion, especially, threshold is one of the most important strategies in water and soil resources management. Gully erosion is one of the most important sources of sediment yield in watersheds that is defined as different thresholds like area-slope or topography. In this paper, the area- slope threshold was investigated in Zahirabad Watershed in Markazi province, Iran. First, based on field surveys and digital elevation model, morphometric characteristics of 14 gullies were measured, accompanied by soil sampling and vegetation cover measurements. Second, homogeneous groups of gullies were defined by factor and cluster analysis and power relations of area-slope was prepared. Results demonstrated that there was no considerable correlation between area and slope of gully watersheds. So, coefficient of determination of creation point and head-cut of gullies were 0.111 and 0.181, respectively. According to the results, the dominant process in creation and head cut development of gullies in Zahirabad was related to flow concentration and rill erosion of high slopes. Considering the prevail of loamy texture of soils land use changes and deterioration of vegetation cover, it is suggested to investigate the optimization of land use schemas, and land cover improvement on sloppy lands with the objective of gully control.
Samad Shadfar; Ali Akbar davoodirad; Hamid Reza Peyrowan
Abstract
Gully erosion is a type of water erosion which causes degradation in both agricultural fields and rangelands as well in arid and semi-arid areas. According the role of soil degradation due to erosion, research objectives were to find out investigation causes gully erosion in Robat Tork Watershed. In ...
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Gully erosion is a type of water erosion which causes degradation in both agricultural fields and rangelands as well in arid and semi-arid areas. According the role of soil degradation due to erosion, research objectives were to find out investigation causes gully erosion in Robat Tork Watershed. In this research three representative gullies were selected in agriculture and rangeland working units. In each working unit, samples taken from nine soil profiles were analyzed for texture, organic matter, gypsum, total lime, pH, EC and SAR. Soil infiltration rate was measured where were drilled profiles in each working unit too, In addition, morphometric characteristics of gullies including length and lateral profiles, top and down width, depth of gully, the cross section, width to depth ratio, the slope of bed, gully length were studied. Results of the study showed that SAR and sodium cation are caused dispersion of soil particles and increasing gully erosion. percentage of clay and silt is 11% and 29% in surface layer representative head cut gully and organic matter is between 0.30% to 1.82% in agriculture unit. In rangeland unit, percentage of clay and sand is 41% and 43% in surface layer representative head cut gully and organic matter is between 0.29% to 0.99%.In rangeland unit, in a specified level, the number of gully is more than agriculture unit. Furthermore, the results showed that TNV in agriculture unit and pH, EC in rangeland unit is more than. In both units depth to wide ratio is more than 1 in every gully. Permeability of soil is 4.25 cm and 3.45 cm in agriculture and rangeland units respectively.
