微地形条件下黄土耕作坡面水蚀发育过程的三维数值模拟与机理研究

Numerical simulation and response of microtopography in the soil erosion prosess, especially the prediction of soil erosion on microtopographic, has gradually been the forefront and hot issues in the field of soil erosion, it is also becoming a scientific problem needed urgently to be addressed in the quantitative study of soil erosion worldwidely. While very few studies have integrated both the evolution of soil erosion and the microtopographic situations. The current researches about the process and mechanism of soil erosion in microtopographic scale are still quite weak and these researches even do not really reveal the relationship between microtopography and soil erosion. As a result, this situation affects people's awareness and understanding about the mechanism of soil erosion. In this project, indoor and outdoor artificial rainfall experiment will be carried out at the loess tillage slope so as to simulate the dynamic evolution process of soil erosion. Simultaneously, high-precision laser scanner is used for collecting the elevation data(in mm scale). Technologies and methods such as geo-statistical, computer simulation,… are adopted to build slope GIS-DEMs. Then the 3D numerical simulation model of micro-topography with their atlas will be established. Sequentially, the research about coupling relationship between microtopography factors and water erosion factors, including their dynamic evolution conditions, are conducted. Finally, a forecast model of soil erosion in microtopographic scale will be designed and explored. This project is aimed to reflect the inherent relationship of microtopography in coordinated with water erosion. The innovative result can be considered as the sublimation of quantitative research of soil erosion and the specialized supplemental information in forming the theoretical concepts of microtopography too. It should be helpful to the transformation and efficient management of slope farmland in the loess region. Also, it can provide scientific guidance to the calculation of runoff, sediment, mass transportation and the simulation on microtopographic scale. In a sense, this project has an important theoretical and practical guidance value. The output is expected to promote academic innovation and development in the field of soil erosion.

微地形数值模拟与水蚀过程的响应和预测是当今土壤侵蚀研究的前沿和热点，也是国际土壤侵蚀定量化研究迫切需要解决的重要科学问题。目前对微地形尺度水蚀过程与机理研究还相当薄弱，至今尚未真正揭示微地形与水蚀之间的关系，影响了人们对水蚀机理的认识和理解。本项目通过室内外人工降雨实验模拟黄土坡耕地微地形水蚀发育的动态过程，运用高精度激光扫描、地统计学、计算机模拟等技术和理论，研究构建坡面GIS-DEM，建立仿真微地形三维数值模拟描述模型及图谱数据库，进而开展微地形与水蚀因子间耦合关系和动态转化的临界条件研究，探索建立反映黄土坡耕地微地形水蚀形态转化关系的预报模型，旨在阐明微地形条件下黄土耕作坡面水蚀演化的内在过程与相互作用机理。研究结果将为水蚀定量化研究增添新的内容，并为该区坡耕地改造与管理及水土资源高效利用提供科学指导，对微地形径流、泥沙和物质迁移等的模拟计算具有重要参考意义，推动学科创新与发展。

微地形数值模拟与水蚀过程的响应和预测是当今土壤侵蚀研究的前沿和热点，也是国际土壤侵蚀定量化研究迫切需要解决的重要科学问题。目前对微地形尺度水蚀过程与机理研究还相当薄弱，至今尚未真正揭示微地形与水蚀之间的关系，影响了人们对水蚀机理的认识和理解。本项目通过室内外人工降雨实验模拟黄土坡耕地微地形水蚀发育的动态过程，运用高精度激光扫描、地统计学、计算机模拟等技术和理论，研究构建微地形条件下黄土耕作坡面DEM及其图谱数据库，进而开展不同耕作措施地表在水蚀发育过程中的时空演变规律研究，阐明了坡耕地地表与降雨、产流、汇流之间的相互作用机理，提出黄土坡耕地水土保持效应。研究结果表明：（1）基于地统计分析-各向异性分析-分形分析相结合的方法，能够较好地揭示黄土耕作坡面空间各点相对高程的时空异质性特征；与半方差函数拟合模型相应的Kriging交叉验证和Kriging插值，可用于模拟真实的微地形地表状况，是微地形高精度DEM（mm级精度）生成的方法。（2）黄土耕作坡面具有强烈或中等自相关的空间变异性、良好的多尺度分形和各向异性特征；结构性因子（人为措施和坡度）对微地形地表时空分布状况的影响远大于降雨的影响。（3）直线坡、25°坡面具有良好的空间自相关性，更容易被侵蚀；等高耕作、15°坡面有较高的空间异质性，具有良好的水土保持效应；随着侵蚀过程从溅蚀、片蚀到面蚀的发育，微地形坡面对侵蚀的抑制作用先降低后有所增加；降雨对地表糙度具有一定的削弱作用。（4）重标极差分析法结合小波分析，可用于预测未来的产流产沙趋势；各耕作坡面的径流量和产沙量序列可能存在30 min左右的主周期；径流量和产沙量与降雨历时存在对数回归关系 （S = alnt + b, R2 > 0.50）。研究结果为微地形条件下水蚀定量化研究提供一定的方法参考，为黄土区坡耕地改造与管理及水土资源高效利用提供科学指导，对微地形径流、泥沙和物质迁移等的模拟计算具有重要参考意义。