Keywords: 
• natural rainfall /
• red-soil slope /
• interflow /
• characteristics of runoff process

Abstract: Interflow output constitutes an important part of the hydrologic process of red soil slopes. In order to study interflow output characteristics on red soil slopes, a large-size field soil infiltration device (Lysimeter) was used to conduct a natural rainfall-interflow production observation experiment over grassland and bare land and at different depths (30cm, 60cm). The results indicated that: ① The retardation time and trailing time of the interflow production process both extended at deeper soil layers, where the compatibility with the rainfall process weakened. The interflow yield, peak value, and production duration of grassland were all larger than those of bare land, and their differences became more obvious under abrupt rainfalls. ② The interflow yield presented a significant positive correlation with the amount of rainfall (R²=0.694 2—0.877 0), but no apparent relationship with the intensity of rainfall. In the case of abrupt and extreme rainfalls, the interflow production process showed a rapid rise of flood peak, while in the case of uniform rainfall the interflow production process was relatively gentle. In the cases of abrupt, extreme, and uniform rainfall, the ratios of interflow yield to surface runoff of bare land were 13.82%, 91.73%, and 159.04%, respectively, while those of grassland were 118.95%, 312.11%, and 368.33%, respectively. ③ With the increasing antecedent soil moisture content, the retardation time of interflow production was shortened, and its peak value and flow increased.