Rainfall and inflow effects on soil erosion for hillslopes dominated by sheet erosion or rill erosion in the Chinese Mollisol region

Erosion agents and patterns profoundly affect hillslope soil loss characteristics. However, few attempts have been made to analyze the effects of rainfall and inflow on soil erosion for hillslopes dominated by sheet erosion or rill erosion in the Chinese Mollisol region. The objective of this study was to discuss the erosive agent (rainfall or inflow), hillslope erosion pattern (sheet erosion or rill erosion) and slope gradient effects on runoff and soil losses. Two soil pans (2.0 m long, 0.5 m wide and 0.5 m deep) with 5° and 10° slopes were subjected to rainfall (0 and 70 mm h –1 ) and inflow (0 and 70 mm h –1 ) experiments. Three experimental combinations of rainfall intensity (RI) and inflow rate (IR) were tested using the same water supply of 70 mm by controlling the run time. A flat soil surface and a soil bed with a straight initial rill were prepared manually, and represented hillslopes dominated by sheet erosion and rill erosion, respectively. The results showed that soil losses had greater differences among treatments than total runoff. Soil losses decreased in the order of RI70+IR70 > RI70+IR0 > RI0+IR70. Additionally, soil losses for hillslopes dominated by rill erosion were 1.7–2.2 times greater at 5° and 2.5–6.9 times greater at 10° than those for hillslopes dominated by sheet erosion. The loss of