沙漠河岸风水复合地貌过程研究 —以库布齐沙漠毛不拉孔兑为例

River banks in deserts are unique geographical units due to the prominent processes of aeolian-fluvial interactions occurring in such environment. On one hand, rivers control the development processes and patterns of aeolian landforms by providing sediment source and space. On the other hand, dune development changes the channels of rivers. However, most of the published research in such area tends to study the landform driving agent either from the perspective of fluvial or aeolian process, separately, rather than combining the two processes together. In this project, the geomorphic process of aeolian-fluvial interactions on desert river banks will be studied taking the example of the Mu Bulag River in the Hobq desert. Multi-methods will be adopted including on site observation and measurement, topographic mapping and remote-sensing image analysis, to analyze the features and changes of different spatial combinations of river and dune landforms and the three-dimensional morphological changes of dunes of different types at different river reaches and geomorphic units, to establish the relationship of dimensional morphological between river channel and sand dunes on banks. Further in-depth analysis of the geomorphic features of sand dunes in different river sections and the role of river processes in the development of dune landforms. Monitoring and analysis of the flow field structure, sediment transport rate, erosion pattern, and overall movement characteristics of sand dunes along rivers, and the influence of aeolian landforms　processes on the river channel morphology. By the end, a coupled landform model will be developed to enable simulations of dunes-river interaction processes which will further improve the understanding towards the implication of such processes on geomorphology.

沙漠河岸是独特的地理单元，在世界主要沙漠中普遍存在，风水复合地貌过程是其独特性的突出表现，一方面，河流通过提供物源和场所控制风沙地貌的发育过程与格局，另一方面，沙丘发育过程改变河道。地貌学家们曾从河流地貌学角度，探究沙漠河道曲流特征，但河岸风沙地貌及其与河道相互作用的风水复合地貌过程尚未得到关注，有待研究。本项目以库布齐沙漠毛不拉孔兑为例，研究沙漠河岸风水复合地貌过程。基于对河道与沙丘地貌形态的表征参数，采用野外调查与定位观测、遥感分析与地面测量等方法，分析不同河段河道形态及其沿岸沙丘地貌形态与格局特征及其空间演变，建立河道与沿岸沙丘的形态学关系。进一步深入分析不同河段沙丘地貌特征，探讨河流过程在沙丘地貌发育中的作用。监测和分析河流沿岸沙丘表面流场结构、输沙率变化、蚀积格局和整体移动特征，探讨风沙地貌过程对河道形态的影响。建立河流-风沙交互作用下，河道与沙丘地貌的耦合发育模式。

风水交互作用是干旱区（广义）最为显著和频繁的地表过程。干旱区沙漠河岸是独特的地理单元，在世界主要沙漠中普遍存在，风水复合地貌过程是其独特性的突出表现，在不同时空尺度上表现不一。本项目以库布齐沙漠毛不拉孔兑为研究区，采用野外调查与定位观测、遥感分析、地形探测、样品测试等方法，调查分析了不同尺度下（大地构造单元、生物气候带、河段、地貌单元）的风水交互作用方式及其在地貌格局，地表沉积物的响应，探明了沙漠河岸风水复合地貌过程的动力机制。结论如下：①在宏观尺度沙海-流域水系下，将中国北方沙漠/沙地与流域水系的地貌格局划分为：I辐合水系－团块状沙地型；II 平行状水系－分散沙地型；III 树枝状水系－斑块镶嵌沙地型；IV 扇状水系－带状沙地型；V 闭流区－破碎状沙地型；②在中尺度河道-沙丘尺度下，不同河型下两岸沙丘地貌格局类型：a弯曲河道—对称式边滩沙丘；b顺直河道—边滩沙丘；c分汊河道—心滩式沙丘；d网状河道—格状镶嵌式沙丘； 微观尺度上单一的河岸沙丘的形成过程为“饼状沙丘→盾形沙丘→新月形沙丘→新月形沙丘链”等演变过程；③不同尺度风水交互作用在地表沉积物上的响应：对于中国北方不同气候带的沙漠河岸沙丘，自西向东地表沉积物的粒度变细，分选性变差，化学风化程度增强，这与西部地区风水交互作用的方式以风力为主，以流动分布沙丘为主，而东部地区以流水作用为主，以固定半固定沙丘分布；同一河流不同河段，由于局地气候、坡向，风向与水流的夹角不同，地表沉积物理化特征呈现出不同的空间分布规律；同一河流断面，自河床至阶地，由于下伏地貌不同、沙丘坡向不同，地表沉积物理化特征上也呈现出不同的空间分布规律。本项研究成果有助于科学认识干旱区风水交互作用的过程与机理，促进风沙地貌与流水地貌的高度融合，丰富和完善沙漠科学和干旱区水文的理论体系；项目的开展对于干旱区绿洲生态保护和防沙治沙工程的布局与实施具有积极的指导和实践意义。