细沟侵蚀过程与径流速度的响应

Rill erosion process and the response of the runoff velocity

利用室内模拟降雨试验,研究了不同坡度条件下细沟发育阶段水沙特征及其与径流速度的响应。研究结果表明,对于杨凌塿土,细沟侵蚀过程大致分为3个阶段,即面状侵蚀期(A阶段)、细沟网络发育期(B阶段)和细沟网络稳定期(C阶段)。侵蚀阶段对径流率的影响不显著,对含沙量影响显著,在A阶段和B阶段含沙量随时间呈增加趋势,在C阶段含沙量逐渐趋于动态平衡状态,该表现形式在大坡度下尤为明显。在不同侵蚀阶段,坡度影响程度不同,在C阶段坡度对细沟侵蚀的影响最为显著。细沟侵蚀过程中,径流速度变化比较复杂,不同坡度不同侵蚀阶段没有明显的规律性。坡度较小时,高流速低频率相对分散的情况集中在A阶段和B阶段;坡度较大时,集中在B阶段和C阶段,说明B阶段是细沟侵蚀的活跃期,在该阶段径流速度的波动性大,大径流速度出现的概率明显增加。

The characteristics of water and sediment and the response to runoff velocity in rill developmental stage under the different slope conditions were studied by using indoor simulated rainfall test. The results show that as for the soil which collected from Yangling, the rill erosion process is roughly divided into three stages, namely, surface erosion period （stage A）, rill network development period （stage B） and rill network stability period （stage C）. The effect of erosion stage on runoff rate is not significant, which has significant effect on sediment concentration. In the A and B stages, the sediment yield increased with time, and in the C stage the sediment concentration increased gradually, this manifestation is particularly evident at large slopes. In different stages of erosion, the influence degree of slope is different, and in the C stage, the effect of slope on the rill erosion is the most significant. During the process of rill erosion, the change of runoff velocity is complicated. There are no obvious regularities in different slope and different erosion stages. In general, when the slope is small, the high flow rate and low frequency are relatively scattered in the A stage and the B stage. When the slope is large, it is concentrated in the B stage and the C stage. It explains the B stage is the active period of rill erosion. At this stage, the fluctuation of runoff velocity is large and the probability of large runoff velocity increases obviously.