雨型和坡长对侵蚀泥沙粒径特征的影响

为揭示降雨和坡长对侵蚀泥沙粒径特征的影响，以不同坡长野外观测试验小区为对象，结合82场降雨资料，以降雨量(P,mm)、最大30 min雨强(I₃₀,mm/h)和降雨侵蚀力[R,MJ·mm/(hm²·h)]为降雨特征指标，利用系统聚类法进行雨型划分(A雨型：大雨量、高雨强、高侵蚀力；B雨型：中雨量、小雨强、中等侵蚀力；C雨型：低雨量、中雨强、中低等侵蚀力),分析了11场降雨事件中侵蚀泥沙的粒径分布特征。结果表明：(1)研究区侵蚀泥沙粒径特征受不同雨型影响，有效黏粒和最终黏粒含量在C雨型下最高，有效砂粒和最终砂粒含量在B雨型下最高，而有效粉粒和最终粉粒含量分别在A和C雨型下最高。(2)坡长对侵蚀泥沙粒径特征的影响存在临界坡长效应(14 m),小于临界坡长时，黏粒级和粉粒级颗粒含量随坡长增加而降低；超过临界坡长后，黏粒级和粉粒级颗粒含量随坡长增加而增加，该效应在最终粒径下更为显著。(3)有效砂粒输移形式受雨型和坡长影响较大，在B雨型下主要以团粒形式输移，在A,C雨型下达临界坡长时以单粒形式输移。侵蚀泥沙的有效粒径颗粒比原坡面土壤细，而最终粒径颗粒则...

Influence of Rainfall Patterns and Slope Lengths on the Characteristics of Eroded Sediment Particle Sizes

To illustrate the influence of different rainfall patterns and slope lengths on the dispersion of soil particles, we took field plots with different slope lengths as the research objects and combined with data of 82 rainfall events to classify rainfalls as 3 types(type A: heavy rainfall, high rain intensity, high erodibility; type B: medium rainfall, light rain intensity, medium erodibility; type C: low rainfall, medium rain strong, medium and low erosion)by using hierarchy cluster based on rainfall(P, mm), maximum 30 min rainfall intensity(I₃₀, mm/h), and rainfall erodibility 〔R, MJ·mm/(hm²·h)〕. The particle size distribution characteristics of eroded sediments in 11 rainfall events were analyzed. The results showed that:(1)the composition of eroded sediment particles was affected by different rainfall patterns; the contents of effective and ultimate clay were the highest under type C, and the contents of effective and ultimate sand were the highest under type B, the content of effective silt was the highest under type A, and the content of ultimate silt was the highest under type C;(2)there was a critical slope length effect(14 m)on the distribution of sediment particles; when the slope length was shorter than the threshold, the contents of clay and silt particles decreased with the increase of slope length; and it would increase with the slope length while the slope length was longer than the threshold; the effect on the ultimate particle size was even more significant;(3)the transport of sand particle was greatly affected by the rainfall type and slope length; under the rainfall type B, the transport of effective sand was mainly in the form of aggregated particle, while in the rainfall types A and C, it was transported in the form of single particle at the critical slope length. The effective particles of eroded sediment are finer compared with the original soil, while the ultimate particles were coarser. On the whole, the particle size characteristics of eroded sediment are affected by different rainfall types and slope lengths significantly. The effective particle size of eroded sediment tends to be finer, while the ultimate particle size tends to coarsen, and there is a threshold effect for the slope length on sediment particles.