Simulation Study of Characteristics of Runoff and Sediment Yield in the Hill Area with Purple Soils

Based on simulated rainfall experiments,the characteristics of runoff and sediment yield were studied on purple soils in the hilly area of Sichuan Basin.Results showed that the time lag of surface runoff increased with increased rainfall intensity and slope gradient and it ranged from 0.7 to 9.5 min.The time lag of subsurface flow ranged from 2.6 to 46.4 min.Rainfall intensity was the most important factor influencing subsurface flow.The cumulated amount of surface runoff increased with rainfall intensity and slope gradient,while the subsurface flow amount decreased with rainfall intensity and slop gradient.Surface runoff receded rapidly and the recession coefficient(k) ranged from 0.41 to 0.66.However,the subsurface flow receded slowly with k ranging from 0.91 to 0.99.Rainfall intensity was the key factor of sediment yield for the same rainfall duration and sediment yield varied from 23.4 to 972.3 g/(m2·h) with increased rainfall intensity.Sediment yield increased with increased slope gradient for the same rainfall intensity.