The impact of slope length on the discharge of sediment by rain impact induced saltation and suspension
The impact of slope length on the discharge of sediment by rain impact induced saltation and suspension
复制标题
DOI：
10.1002/esp.1828
复制
发表时间：
2009-08
影响因子：
3.3
通讯作者：
P. Kinnell
中科院分区：
文献类型：
--
作者：
P. Kinnell
利用降雨影响流中雨滴驱动侵蚀的机制模型进行了模拟，其中颗粒通过悬浮、雨滴诱导跳跃和流动驱动跳跃进行了模拟。高强度暴雨和弱强度暴雨的结果都表明，由于水流深度对雨滴向河床输送能量的影响，当雨滴引起的跃移输送颗粒时，泥沙浓度下降，从而单位面积的土壤流失量随坡长而减少。然而，当在某一事件中偶然超过导致流动驱动跃变的临界速度时，这种下降就会逆转。模拟是在光滑表面和单个液滴大小上进行的，但一般关系可能适用于由大范围液滴大小组成的雨。虽然径流的产生并不总是均匀的，但一般来说，流速随坡长而增加，因此，通常情况下，在一次事件中，颗粒在被排出之前的距离随坡长而增加。通常认为，坡长对单位面积土壤流失量的影响随坡长变化的幂次大于零且小于1·0。模拟结果表明，坡长对输沙量的影响高度依赖于降雨持续时间-强度-入渗条件变化引起的径流响应变化，而不是地块长度本身。因此，当坡面侵蚀发生时，使用坡长正数接近于零的方法来预测单位面积的土壤流失量可能不像通常预期的那样有效。雨影响流的侵蚀是一个复杂的过程，在分析与自然和人工条件下雨影响流相关的实验结果时，需要考虑到这种复杂性。版权所有©2009 John Wiley & Sons， Ltd
Simulations using a mechanistic model of raindrop driven erosion in rain‐impacted flow were performed with particles travelling by suspension, raindrop induced saltation and flow driven saltation. Results generated by both a high intensity storm, and a less intense one, indicate that, because of the effect of flow depth on the delivery of raindrop energy to the bed, there is a decline in sediment concentration, and hence soil loss per unit area, with slope length when particles are transported by raindrop induced saltation. However, that decline is reversed when the critical velocities that lead to flow driven saltation are episodically exceeded during an event. The simulations were performed on smooth surfaces and a single drop size but the general relationships are likely to apply for rain made up of a wide range of drop size. Although runoff is not always produced uniformly, as a general rule, flow velocities increase with slope length so that, typically, the distance particles travel before being discharged during an event increase with slope length. The effect of slope length on soil loss per unit area is often considered to vary with slope length to a power greater than zero and less that 1·0. The simulations show that effect of slope length on sediment discharge is highly dependent on the variations in runoff response resulting from variations in rainfall duration‐intensity‐infiltration conditions rather than plot length per se. Consequently, predicting soil loss per unit area using slope length with positive powers close to zero when sheet erosion occurs may not be as effective as commonly expected. Erosion by rain‐impacted flow is a complex process and that complexity needs to be considered when analysing the results of experiments associated with rain‐impacted flow under both natural and artificial conditions. Copyright © 2009 John Wiley & Sons, Ltd.