Effects of Up-Slope Runoff and Sediment on Rill Hydraulic Parameters

A dual-box system,consisting of a feeder box,located at up-slope,and a test box,located at down-slope was used to quantify impacts of runoff and sediment from up-slope on rill hydraulic parameters under different rainfall intensities of 50,90 and 130 mm/h.The results showed that up-slope runoff discharging into rill channel at down-shope section or an increase of rainfall intensities resulted in that rill flow shifted from stratum flow into turbulent flow.Runoff and sediment from up-slope caused a great increase of rill flow velocity and Reynolds number,and an obvious decrease of rill flow Daycy-weisbach coefficient.For these reasons,up-slope runoff discharging into rill channel at down-slope section caused a great increase of sediment delivery by rill flow.Meanwhile,the relation between rill flow velocity,Reynolds number and Daycy-weisbach coefficient,and net rill erosion amount caused by up-slope runoff was analyzed,respectively.A statistical model among the net rill erosion amount caused by up-slope runoff and relative increment of rill flow velocity,Reynolds number,and relative decrement of Daycy-weisbach coefficient was established.