黄土坡面侵蚀泥沙沉积过程与模拟

Soil erosion processes by water on hillslopes involve the sub-processes of detachment, transport and deposition of soil materials, which are influenced and restricted by each other. However, the investigations on the deposition process of eroded sediment were insufficient, due to the limitation of the experiment and monitoring technique. Until now, the internal law of the deposition process is still unclear. In view of the deposition process of eroded sediment on loess slope, the typical loess is selected in this project for investigation. The quantitative research on the internal mechanism and changing laws of deposition process of eroded sediment on loess hillslope is conducted through the indoor simulating experiment. The specific purpose of the this project is to quantify the law of the sediment deposition profile changes with the time, spatial distribution characteristics of deposition sediment particles, sediment sorting characteristics of the deposition sediment particles during the deposition process of eroded sediment on loess hillslope. Moreover, the physics-based models are to be established for the simulation of the deposition process of the eroded sediment on loess hillslope. This research will be benefit to improve the modelling accuracy of the process based soil erosion model on loess slope, improve our knowledge of the deposition process of the eroded sediment on loess hillslope, and to a certain extent, enrich slope soil erosion process research in China.

土壤颗粒分离、泥沙输移和沉积是坡面土壤侵蚀过程中三个相互影响又相互制约的子过程。受试验条件和观测手段的限制，目前坡面侵蚀泥沙沉积过程的定量化研究相对较少，坡面侵蚀泥沙的沉积过程与规律尚不清晰。本项目针对黄土坡面侵蚀泥沙沉积过程，选取黄土高原典型黄土为研究对象，通过室内人工模拟试验，定量研究不同坡度和不同水动力条件下侵蚀泥沙沉积剖面随时间的变化规律、沉积泥沙颗粒空间分布特征、沉积泥沙颗粒分选特征和侵蚀泥沙沉积过程模拟研究，系统揭示黄土坡面侵蚀泥沙沉积过程的内在机制及其空间分布特征，为提高黄土高原土壤侵蚀过程模型模拟精度提供物理基础，为完善坡面泥沙沉积过程及机理奠定基础，可在一定程度上丰富我国坡面土壤侵蚀过程研究。

针对目前坡面侵蚀泥沙的沉积过程与规律尚不清晰的关键问题，本项目利用室内模拟人工试验，结合三维激光扫描技术和摄影测量技术，明确了土壤侵蚀-输移-沉积过程和变化特征，并验证了高精度三维激光扫描技术在进行定量监测黄土坡面侵蚀沉积空间分布特征方面的可行性。本研究发现，黄土坡面沉积分布范围和沉积面积均与坡度呈负相关，绥德砂黄土则更容易发生沉积，沉积厚度主要集中在0 ~ 4 mm；总体上，这种相似性规律也存在于侵蚀发生后的土壤表层粉砂和细砂含量在空间的变化上，侵蚀粒度以粉砂和细砂为主;但这两种粒径的选择机制在两种土壤中存在明显差异；片蚀过程可被划分为输沙能力限制阶段、剥蚀能力限制阶段I和剥蚀能力限制阶段II共3个侵蚀阶段，其中剥蚀能力限制阶段I的侵蚀量占绝对优势；对于相同侵蚀限制阶段，坡度增加会明显增加含沙量，但对于产沙量作用不明显；细沟侵蚀与片蚀在坡面的空间分布通过影响径流的动力作用，引起侵蚀-沉积在空间上的变化，即当土壤侵蚀由受径流输沙能力控制阶段向剥蚀能力限制阶段演变时，及可发生沉积现象。在本项目的支持下，发表论文9篇（其中SCI论文4篇，均为1区，EI论文1篇），3篇SCI论文和2篇中文核心论文在外审中，培养研究生6名，其中已毕业3名，预计2022年6月毕业2名（目前已经完成硕士论文初稿），预计2023年6月毕业1名。本研究可为深化黄土高原土壤侵蚀机理，提高土壤侵蚀预报模型精度提供物理基础，也可为坡面水土保持措施的科学布局提供科学依据。