黄土丘陵沟壑区不同空间尺度地貌单元水沙耦合机制

The different topographical units of different spatial scales in the Loess Hilly-Gully region were not only the erosion units but also the runoff and sediment delivery units. With the interreaction driving force of rainfall, runoff and sediment transportation, the different topographical units formed a dynamic coupling system. In this system, the process of the soil erosion and sediment delivery in the different topographical units was of particular physical mechanism. At present, the different topographical units were separated and most of research about soil erosion process was aimed at each unit independently. And lack of the systematic research on the runoff and sediment coupling relationship between each different topographical units during soil erosion and sediment delivery process. Bearing this in mind, based on the theory of soil erosion, sediment dynamics and hydraulics, with the support of 3S technology, this project selected the "slope-gully-watershed" system in the hilly-gully as the study area.First, using Qiaogou and Peijiamao watershed in that region as prototype for observation and making use of the observation facilities therein including four hydrological staions and five large-scaled field runoff plots which located in different togographical units, the runoff and sediment coupling relationship between different topographical units was analysed systematically.Moreover,the runoff and sediment coupling dynamic mechanism was studied by rainfall simulation experiment.In this way, we hope to provide theory support to establish the soil erosion model of different spatial scales and to optimize the soil and water conservation measurement in watershed management in the Loess hilly-gully region.

黄土丘陵沟壑区不同空间尺度地貌单元不仅是侵蚀单元，而且是水沙传递单元，在降雨-径流-泥沙物质迁移转换和驱动下，不同空间尺度地貌单元形成动态耦合的侵蚀产沙复杂系统。系统内不同地貌单元的侵蚀产沙过程具有不同的物理机制，目前大多研究独立地貌单元的侵蚀产沙过程，缺乏从系统的角度研究不同地貌单元之间的侵蚀-搬运-沉积过程及其耦合关系。鉴于此，本项目以土壤侵蚀学、泥沙动力学和水力学等学科的理论为基础，以3S技术为支撑平台，采用野外宏观勘测、定位动态监测、人工模拟降雨和理论分析相结合的研究方法，以"坡面~沟道~流域"系统作为研究对象，描述不同空间尺度地貌单元间的侵蚀产沙耦合关系，揭示不同地貌单元之间水沙搭配关系的关联性，阐明不同空间尺度地貌单元水沙耦合的水动力学机制。其研究成果可为建立不同空间尺度土壤侵蚀预报模型提供理论支撑，同时为黄土丘陵沟壑区流域治理措施优化配置提供科学依据。

黄土丘陵沟壑区不同空间尺度地貌单元不仅是侵蚀单元，而且是水沙传递单元，在降雨—径流—泥沙物质迁移转换和驱动下，不同空间尺度地貌单元形成动态耦合的侵蚀产沙复杂系统，系统内不同地貌单元的侵蚀产沙过程具有不同的物理机制。鉴于以往研究多针对独立地貌单元的侵蚀产沙过程开展研究，缺乏从系统的角度研究不同地貌单元之间的侵蚀—搬运—沉积过程及其耦合关系。因此，本项目以土壤侵蚀学、泥沙动力学和水力学等学科的理论为基础，采用野外定位监测、室内模拟降雨试验、水文分析、地统计数理分析相结合的方法开展研究。野外观测以黄土丘陵区裴家峁沟典型小流域的梁峁坡、沟坡不同地形部位径流小区、全坡面径流场及桥沟、裴家峁沟水文站实测径流泥沙资料为基础，系统分析“坡面~沟道~流域”系统不同时空尺度下各地貌单元侵蚀输沙及水沙关系特征，阐明不同时空尺度下各地貌单元水沙关系特征及其差异性；基于降雨相似性、土壤特性相似和侵蚀产沙作用过程相似的原则，提出了流域地貌形态概化模型的设计思路，按照水平比尺1:60、垂直比尺1:50，塑造具有二级沟网的桥沟流域概化模型，分析了不同地貌单元（坡面、支沟、流域）产流产沙过程，阐述了不同地貌单元水动力学特征和地貌分形特征，选择来沙系数作为不同地貌单元水沙关系指标，分别建立不同空间尺度地貌单元来沙系数与水动力学参数、地貌分形维数和地貌信息熵之间的定量关系，从水动力学和地貌形态演化角度揭示不同空间尺度地貌单元水沙关系发生机制。研究成果对进一步认识黄土丘陵区土壤侵蚀过程及其发生机理，科学布设水土保持综合治理措施，对于黄土高原生态环境治理具有重要的科学意义和生产应用价值。