Investigation of Gravel Fragment Effect on Runoff Yield and Soil Erosion Using Rainfall Simulation (Case study: Watershed of Almas Bridge, Ardabil)

Soil erosion is one of the basic environmental problems in the developing country such as Iran and can be destructive effects on ecosystems. The aim of this study was to investigate the gravel fragment effects on runoff and soil loss in the watershed of Almas Bridge, Ardabil. For this research after the surveys in the area, three class slopes (6, 15 and 22%) were identified in the region. In each slope class, treatments consisted of gravel coverage zero, 10, 20 and 30% were applied. A factorial experiment was carried out in a randomized complete block design. Results showed that the maximum runoff volume, soil loss, sediment concentration and runoff coefficient were in the control treatment (without the gravel fragment coverage) in the slope of 22% and the minimum of them were in treatment with 30% of gravel fragment coverage in the slope of 6 percent. The results depicted that the runoff volume and soil loss were decreased 96% and 519%, respectively, using 30% gravel fragment coverage in compared with the control treatment. On the other hand, the finding of this research illustrated that the generated volume of runoff on the slope of 22% is 37 and 107 percent more than the slope of 15% and 6%, respectively. In additional, 20 and 30% of gravel fragment coverage in the slope of less than 15% were shown the most effect on the soil loss, sediment concentration and runoff volume.