Document Type : Research Paper
Authors
1 Ph.D. Student, Faculty of Natural Resources, Tarbiat Modares University, Iran,
2 Associate Professor, Faculty of Natural Resources, Tarbiat Modares University, Iran
3 Assistant Professor, Soil Conservation and Watershed Management Research Institute, Iran
4 Assistant Professor, Faculty of Mathematical Sciences, Tarbiat Modares University, Iran
Abstract
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.
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