Effects of Slope Length on Runoff under Artificial Rainfall of Variable Rainfall Intensity

Rainfall,infiltration and runoff are very important parts of the water cycle,and slope length is one of the most important factors effecting runoff generation.In this study,plots of 1～10 m long were selected to analyze the effects of slope length on runoff under artificial rainfall of variable rainfall intensity.The results showed that:(1) Slope length had no significant effects on the time of runoff generation.The times of runoff generation in the dry run and wet run were about 21 min and 1.1 min,respectively;(2)As a whole,the relationship between interval runoff depth and slope length was different at different rainfall duration and intensity.Firstly,during the time from runoff generation to 40 min after rainfall initiation,because of low soil moisture and hence high infiltration,the interval runoff depth decreased significantly with increased slope length;Secondly,during the 40～90 min of rainfall,the average rainfall intensity was much higher,and there is little difference in runoff depth for different slope length;Finally,the interval runoff depth showed a downward trend with the increasing slope length due to the low rainfall intensity between the rainfall duration of 90～120 min.These results are helpful in better understanding the process of runoff generation on hillslope.