地面覆盖条件下雨强和坡度对红黏土坡面侵蚀过程的影响

Influence of Rainfall Intensity and Slope on Red Clay Slope Erosion Under Mulching Conditions

为揭示地面覆盖条件下第四纪红黏土坡面在不同雨强和坡度时的侵蚀变化规律,选取3个降雨强度(1.0,1.5,2.0 mm/min)和3个坡度(10°,15°,20°),通过人工模拟降雨试验,分析坡面产流、产沙、入渗特征,并以15°为例计算覆盖坡面的减流减沙效益。结果表明:(1)坡面产流时间随雨强和坡度增加而提前,覆盖对产流时间有明显的滞后作用,雨强的增加会削弱覆盖延缓产流的作用;坡面径流率呈现前期增长,后期趋于稳定的变化特征;(2)当坡度一定,雨强从1.0 mm/min增加至2.0 mm/min,累积侵蚀量增加1.89~2.96倍;雨强一定,坡度从10°增加至20°,累积侵蚀量增加1.91~3.45倍;(3)坡面初始入渗率和入渗总量随坡度的增加而减小,而雨强的增大会增加坡面初始入渗率,减少入渗总量;(4)15°条件下覆盖坡面的径流量和泥沙量较裸坡平均减少50.26%和95.31%,松针覆盖的水土保持效益显著,且减沙效应大于减流效应;(5)坡度对覆盖坡面累积产流量和累积产沙量的影响程度大于雨强,不同雨强、坡度下累积径流量与累积产沙量呈现幂函数关系(R2>0.97)。研究结果可为南方红壤丘陵区林下水土流失治理与生态恢复提供参考。

In order to reveal the erosion variation law of the Quaternary red clay slope under different rainfall intensities and slope gradients in mulching conditions, three representative rainfall intensities (1.0, 1.5, 2.0 mm/min) and three typical slope gradients (10°, 15°, 20°) in red soil hilly area southern China were selected. The characteristics of runoff, sediment yield and infiltration were analyzed by artificial simulation rainfall experiment. Moreover, taking 15° as an example to calculate the effect of reducing the flow and sediment on the slope. The results showed that: (1) The time producing runoff was advanced with the increase of rainfall intensities and slope gradients. The mulching had obvious hysteresis effect on the runoff yield time. However, the increase of rainfall intensities would weaken the effect of mulching on delaying runoff production. The runoff rate increased in the early stage and become stable in the later stage. (2) At the same slope gradient, the rainfall intensities increased from 1.0 mm/min to 2.0 mm/min, and the total amount of sediment yield increased by 1.89~2.96 times. When the rainfall intensity was constant, and the slope gradients increased from 10° to 20°, the total amount of sediment yield increased by 1.91~3.45 times. (3) The initial infiltration rate and the cumulative infiltration of soil decreased with the increase of slope gradients. While the increase of rainfall intensities increased the initial infiltration rates of mulched slope and reduce the cumulative infiltration. (4) Under the condition of 15°, the runoff and sediment volumes of the mulched slope decreased by 50.26% and 95.31% respectively, and the soil and water conservation effect of pine needle mulching was significant. In addition, the sand reduction effect was greater than the flow reduction effect. (5) The influence of slope gradients on the cumulative runoff and sediment yield of mulched slope was greater than that of rainfall intensities. There was a power function relationship(R2>0.97) between the cumulative runoff and sediment yield under different rainfall intensities and slope gradients. These results could provide reference for soil erosion control and ecological restoration in the red soil hilly region of southern China.