| Abstract: | Raindrop size, rainfall intensity and runoff discharge affect the detachment and transportation of soil particles. Among these three factors, the rainfall intensity seems to be more important because it can change other two factors. Storm patterns can be determined by changing the rainfall intensity during the storm. Therefore, the objective of this research is to test the influence of storm pattern on runoff, soil erosion and sediment concentration on a rangeland soil slope under field rainfall simulation. Four storm rainfall intensity patterns were selected for examining the effects of variations in storm event characteristics on soil erosion processes. The selected storm patterns were: I(45, 55 and 70 mm h~(-1)); II(45, 70 and 55 mm h~(-1)); III:(70, 55 and 45 mm h~(-1)); and IV(55, 45 and 70 mm h~(1)). The last pattern is a new one instead of the uniform pattern which has been sufficiently studied in previous researches. The experiments were conducted in field plots(in Kojour watershed, Mazandaran Province, Iran) with an area of one square meter and an constant slope gradient of 18%, surrounded by galvanised sheets. Following the nonuniform prioritization of the storm patterns for the studied variables, time to runoff(IIIIVIII), runoff volume(IIIIVIII), sediment concentration(IVIIIIII) and soil erosion(IIIIVIII)), it can be generally inferred that each pattern has specific effect on soil erosion processes during a storm. The results of the general linear model(GLM) test indicated that the effects of storm pattern on time to runoff, total runoff volume, runoff coefficient and soil erosion were significant at a level of 99%. The Duncan test showed that the storm patterns can be divided into three groups of III, IV; II; I(for time to runoff), I, II; IV, III(for runoff coefficient), and I; II; IV, III(for runoff volume and soil erosion). |
