连续极端暴雨事件下小流域侵蚀泥沙流失规律研究

Study on the law of erosion and sediment loss in continuous extreme rainstorm events in the Loess Plateau

近年来,随着极端降雨事件的频发,原位土壤伴随着侵蚀大量的迁移流失,因此,建立一个基于水力学特征侵蚀泥沙流失的经验模型具有重要的意义。为解决这一问题,在黄土高原选择坡度相近的4种植被演替类型并以裸地为对照开展野外原位冲刷试验。在连续的冲刷条件下,首次冲刷的泥沙浓度、泥沙损失量最大,荒地泥沙总损失量最高,达到14.62 kg,而苜蓿泥沙总损失量最低,仅为0.49 kg。在所选取的5个水力因子中,仅平均流速与泥沙浓度和泥沙损失量之间有显著相关性。受流速控制的砂粒的选择性运移导致了流速与侵蚀泥沙的相关性。根据水力因子和侵蚀泥沙的关系,建立了基于水动力的泥沙损失模型,所有预测值都可以与测量值吻合良好。基于水动力的泥沙损失经验模型可以作为基于物理的泥沙模型的重要参考,也可以为坡面发生严重侵蚀时的侵蚀泥沙损失预测提供思路。

In recent years,with the frequent occurrence of extreme rainfall events,a large amounts of in-situ soil migration and loss have been accompanied by erosion;therefore,it is of great significance to establish an empirical model of erosion and sediment loss based on hydraulic characteristics.In order to solve this problem,four planting succession types with similar slopes are selected in the Loess Plateau with the bare land used as a control to carry out the field in situ erosion test.Under continuous scouring conditions,the first scouring sediment concentration and sediment loss are the largest,and the total loss of wasteland sediment is the highest,reaching 14.62 kg,while the total loss of the land for growing alfalfa is the lowest,only 0.49 kg.Among the five selected hydraulic factors,only the average flow velocity has a significant correlation with the sediment concentration and the amount of sediment loss.The selective migration of sand grains controlled by flow velocity leads to the correlation between flow velocity and eroded sediment.According to the relationship between hydraulic factors and eroded sediment,a sediment loss model based on hydrodynamics is established,with all predicted values in good agreement with the measured values.The hydrodynamic-based sediment loss empirical model can be used as an important reference for the physical-based sediment model,and can also provide ideas for the prediction of erosion and sediment loss when severe erosion occurs on the slope.