Impact of Slope Length on Soil Erosion under Different Rainfall Intensity in A Hilly Loess Region on the Loess Plateau

The relationship between soil erosion and slope length may change with rainfall intensity.In this paper,data of runoff plots in Tuanshangou subbasin was used to study this issue.The influence of slope length on soil erosion under different rainfall intensity was analyzed,and then the critical slope length of soil erosion was discussed.The results showed that the relationship between soil erosion and slope length changed with rainfall intensity.The relationship between the slope length and soil erosion was different when I30 was either more than 0.21 mm min-1 or less than 0.21 mm min-1: when I30 was less than 0.21 mm min-1,i.e.low rainfall strength,with the increase of slope length from 20 m to 60 m,soil erosion modulus decreased,and the changing trend of soil erosion modulus against slope length was identical with that of runoff modulus against the slope length;when I30 was more than 0.21 mm min-1,i.e.high rainfall strength,with the increase of slope length from 20 m to 60 m,soil erosion modulus increased at first and then stabilized,and the change of soil erosion modulus against slope length was identical to that of average runoff sediment concentration.The critical slope gradient of soil erosion was non-fixed value,which was a function of I30.