Experimental study of the velocity profile of rill in the loess region
利用坡面水蚀精细模拟降雨试验，对黄丘区陡坡（20°）条件下细沟流速分布特征进行了研究。通过对细沟形态演变过程的观察与分析， 同时结合试验中对细沟间及细沟内流速的观测， 给出了细沟发育过程中坡面流速沿程分布以及细沟内关键位置的流速分布。结果表明，细沟间流速分布基本不受细沟发育程度的影响，而细沟内水流流速与细沟发育过程之间存在互馈关系，首先坡面漫流向集中股流的转化促使细沟发育，会导致细沟内流速的增加，但随着细沟的进一步发展，汇流面积减小，沟床形态阻力及沟底跌坎消能作用增大，细沟流速又会逐渐减小，沟床形态阻力与径流集中产生的流速增量二者间的相互对比关系影响着细沟内水流速度。
The flow velocity distribution under the condition of steep slope （20°） is studied by using the method of indoor fine simulated rainfall experiment. Through the observation and analysis of the rill morphology evolution and the overland flow velocity during the experiment，the variation rule of the flow velocity during the rill formation and development was studied. The results show that the overland flow velocity between the rills is not affected by the degree of rill development，but there is a relationship between the flow velocity within the rill and the rill development. First，the emergence of the rill will lead to an increase of runoff in the rill，but with the rill development，the confluence area decreases，the rill bed morphological resistance increases，resulting in the gradual decrease of the rill flow velocity. The reciprocal contrast between the rill bed morphological resistance and the flow velocity increment caused by runoff concentration affects the flow velocity in the rill.