坡面细沟侵蚀产沙时空分布规律试验研究

Study on spatial and temporal characters of rill erosion on slope

利用放水冲刷试验结合稀土元素(REE)示踪技术对坡面侵蚀产沙特征及其时空变化进行了研究。结果表明:在径流冲刷下,坡面侵蚀产沙可分为三个不同的阶段并对应不同的产沙特征。其空间变化表现为,在6°、9°情况下,坡面不同坡段的相对侵蚀量沿下坡方向呈现出先减小后增大的趋势;在12°小流量情况下,坡面各坡段的相对侵蚀量与坡度较小的情况相似,当流量较大时,坡面各不同坡段的相对侵蚀量随坡长的增大而减小。但坡面最下端坡段的相对侵蚀量总是随着冲刷历时的延长而减小,其余各坡段的相对侵蚀量则呈现出缓慢的波动式上升。

Combined with the runoff scouring method and the rare earth element (REE) technology, the temporal and spatial variation laws of the sediment yield on slope are studied in this paper. The results show that the process of sediment yield on slope can be divided into the following three stages, interrill erosion stage, intensive rill erosion stage and rill erosion declining stage. The results indicated that the ratio of the amount of sediment yield in the various period to the amount of total sediment yield augments at the beginning and decreases at last during the runoff scouring experiment under the different flow discharge and the different slope gradients. Under the same flow discharge, the maximum value of the ratio shows a tendency of appearing in advance with the slope gradient increasing. The intensive rill erosion stage accounts for the main sediment yield, which contribute 52%～75% to the total sediment yield in the whole experiment. The relative erosion mass of the different section along the slope decreases at first and increases at last during the runoff scouring experiment. Experiment on the steeper slope with smaller flow discharge indicates that the relative erosion mass of the different section along the slope is similar to that on the gentle slope. When the flow discharges is larger, the relative erosion mass decreases with the length of slope increasing. The temporal variation of sediment yield on slope is that the relative erosion mass at the bottom section of the slope decreases with experimental time length of the experiment, while the relative erosion mass on other section increases fluctuantly.