黄土坡面细沟形态变化及对侵蚀产沙过程的影响

为揭示细沟形态对侵蚀产沙过程的影响,选取66、94、127 mm/h三个雨强条件,对20°陡坡坡面进行了坡面水蚀精细模拟降雨试验,选取沟长、沟宽、沟深等指标刻画细沟形态随降雨历时的变化规律。结果表明:1)降雨强度对细沟长度的影响显著,细沟宽度变化受降雨历时的影响较大,细沟深度的变化对降雨强度表现出较强的分异规律。2)细沟形态参数之间不是相互独立的,存在明显的相关关系,说明细沟形态的演变是一个多维度过程。3)细沟的形成和发展与坡面水沙过程关系密切,细沟形态参数与含沙量、侵蚀速率之间均存在较显著的对数函数关系。该研究可以为细沟侵蚀动态模型的建立提供基础数据。

Rill morphology change and its effect on erosion and sediment yield on loess slope

Abstract: The rill morphology changes directly affect the slope hydrological process, and thus forms a mutual feedback effect with runoff yield and concentration, sediment yield and transport. This process embodies the relationship between the elements of water erosion dynamics on the slope, and is a key scientific problem in understanding the physical process of erosion and sediment yield. Morphological development of rill on slope forms a micro relief dynamic response system with soil erosion driven by rainfall. To reveal the formation mechanism of this system, scientific quantification is the key problem. In the past research, one-factor quantification parameter based on mathematical statistics was used, which was hard to express the complexity of the whole system effectively. In this paper, the influence of rill morphology evolution on runoff and sediment process was studied. The rainfall, rill evolution, runoff and sediment yield were used as a hydrodynamic coupling system to study the rill morphological characteristics and implementation methods, to reveal the law of spatial and temporal differentiation of rill morphology, and clarify the quantitative response of rill morphology to rainfall-runoff and sediment yield. The aim of this study was to break through the unresolved spatial variability problem in the existing water erosion prediction model, and to provide scientific basis for the prediction of soil erosion process. The indoor simulated rainfall experiment was conducted to reveal the variation regularity of the rill boundary and the response of the erosion and sediment yield under the fixed slope gradient (20°) and 3 rainfall intensities (66, 94, 127 mm/h). The parameters such as rill cumulative length, mean width and depth were used to describe the change of the rill morphology with the rainfall. Results show that the effect of rainfall intensity on rill length is significant, the change of rill width is influenced by the rainfall duration, and the change of rill depth shows a strong differentiation rule with the rainfall intensity. Rill morphology parameters are not independent of each other, and there is a clear correlation between them. This shows that the evolution of rill morphology is not a one-dimensional development process, but a multi-dimensional change process. Sediment yield is affected by the development of rill. There is a logarithmic function relationship between the rill morphology and the sediment concentration and erosion rate. The results show that the formation and development of the rill are closely related to the water and sediment yield on the slope, and the influence of rill forwarding, rill wall expansion and rill bed undercutting on the sediment yield is basically the same. This study can provide basic data for the establishment of rill erosion dynamic model.