细沟形成对坡面产流产沙过程的影响

Effects of rill development on runoff and sediment yielding processes

为探明细沟形成条件下不同土壤坡面水沙变化特性,利用室内模拟降雨试验,分析了塿土和黄绵土在细沟发育及已有细沟条件下的水沙过程变化规律。结果表明,塿土产流快,易形成细沟,细沟发育有明显的规律性,在坡面上呈平行状分布,细沟密度与坡度密切相关,细沟存在会延长产流时间;黄绵土产流慢,较难形成细沟,细沟发育随机性大。细沟发育对产流过程没有明显影响,土壤入渗快慢是两种土壤产流过程存在差异的主要原因。细沟发育程度加剧,会使塿土含沙量的增加速度加快,达到稳定含沙量的时间提前,坡面已有细沟只对稳定含沙量有明显影响,细沟密度增加会使稳定含沙量提高;黄绵土含沙量的变化主要取决于细沟发育过程中的随机性,当细沟侵蚀以崩塌作用为主时,含沙量会出现急剧增加,即使雨强较小,也会产生严重的土壤侵蚀。

In order to understand the runoff-sediment yielding processes of rill erosion for different soils, the charac- teristics of runoff and sediment yield in rill development for Lou soil （silty clay loam） and loess soil were studied un- der different slope gradients and simulated rainfall conditions. Results show that the runoff generation occurred earlier and rills formed more easily within Lou soil than within loess soil. The rill formation exhibited a regular parallel distri- bution. The degree of rill development increased as the gradient increased, which could prolong the time of runoff gen- eration. For loess soil, however, it was hard to generate runoff and induce rill formation. The rills that did form exhibi- ted a random orientation. The processes of rill development did not have a significant effect on runoff yield ; the soil in- filtration rate was the major factor causing the difference in the runoff generation processes in the two soils. For Lou soil, the rate of sediment production increased with an increase in the degree of rill development. Sediment production stabilized early, and sediment concentration increased as rill density increased. For loess soil, the sediment concentra- tion process largely depended upon the randomness in the rill development process. When the rill erosion was based on collapse, a sharp increase was noted in sediment concentration, where even low rainfall intensities could cause signifi- cant soil erosion.