Intra-storm Variability of Coefficient of Variation of Runoff and Soil Loss in Consecutive Storms at Experimental Plot Scale

Quantification of runoff and soil loss variabilitities are important aspects of hydrological processes. The present study was designed to evaluate the effect of six consecutive storms on variability of descriptive characteristics of runoff and soil loss under different rainfall intensities. To achieve the objectives, a set of laboratory experiments were conducted using rainfall simulator and a 6 x 1-m erosion plot with a depth of 0.5 m and a slope of 5%. The rainfall intensities of 30 and 90 mm/h were applied to a silt loam soil sampled from Kojour rangeland watershed, northern Iran. The results showed a decreasing trend in Coefficient of Variation (CV) of runoff volume with increase in rainfall intensity from almost 50 to 28%. A decreasing trend was also observed for CV of soil loss in consecutive storms from almost 65 to 50% under rainfall intensity 30 to 90 mm/h. The results further indicated a 1.8- and 1.3-times increase respectively for CV of runoff volume and CV of soil loss under low intensity compared to those of 90 mm/h in different consecutive storms. The comparative analysis of the results using One-Way ANOVA also verified significant difference (p > 0.05) among runoff amounts in both rainfall intensities except in 2nd and 6th consecutive storms. In addition, amounts of soil loss were not significantly (p > 0.05) different in 3rd, 4th and 6th consecutive storms under rainfall intensities of 30 and 90 mm/h.