The Heilaigou basin, located in the Inner Mongolia of China, is predominantly influenced by the ae-olian-fluvial actions, with complicated sediment transport conditions on the mainstream riverbed. In order to identify the relationship between sedimentary particles and geomorphic processes, mechanisms for the formation of char-acteristics of grain size composition were investigated by analyzing grain size parameters and external dynamic geomorphologic features. Firstly, the grain size parameters of the riverbed, stream power, maximum grain size of the wind-blown particles and HI values of the mainstream channel were calculated and analyzed, and they were used to establish multiple regression functions of grain size parameters in order to determine the effects of wind and river actions on particles. The results show that sediments in different reaches are formed in different environments:the upper stream is controlled by fluvial and aeolian processes; the sorting properties of riverbed sediments in the middle stream are worse than those in the upper stream since they are affected mainly by fluvial processes as in-dicated by the larger stream power there; and the particles on the downstream riverbed are likely contributed by the Kubuqi Desert. The size of particles on the riverbed depends on the hydrodynamic conditions, but is not signifi-cantly associated with the evolution of landform. Sorting is significantly related to both the hydrodynamic conditions and wind actions. Riverbed deposits brought in by winds likely become finer from the lower to the upper reaches, which are not coarser than 0.88φ. Generally speaking, the stream power has a major effect on sedimentation characteristics of the riverbed, followed by wind power.%黑赖沟流域位于内蒙古风-水两相交互侵蚀区域,主河道的泥沙输移特征较为复杂.为了分析河道沉积粒度与地貌过程的关系,文中主要通过探讨粒度参数与外营力特征的关系对沉积粒度的成因机制进行了研究.在分析过程中首先对河床沉积粒度参数、风成颗粒的最大粒径、河流功率和面积-高程积分值沿河道方向的连续变化值进行了计算,分别对不同河段的外营力活动特征进行分析,并以此为基础,将粒度参数作为因变量,其余三者作为自变量,建立了多元回归函数.分析结果显示不同河段外营力对河床沉积物的影响特征不同,其中上游河段河床沉积物主要受径流和风力作用影响;中游河段主要受河流作用影响,沉积颗粒的分选性最差,沉积颗粒的大小与河流功率关系密切,粗质颗粒难以被搬运到下游河段;下游河段受库布齐沙漠影响的可能性较大.就河道整体特征来讲,河道两侧地貌的侵蚀演化特征对河道内的沉积颗粒影响不显著,河床沉积物特征主要受河流和风力作用,其中沉积颗粒的平均粒径主要反映了河流功率的大小,风力作用对沉积颗粒的分选性具有一定影响.河道内的风成颗粒主要来自流域西部,粒径值不会大于0.88φ,其中下游河段内的风成颗粒比上游河段略粗.总而言之,河流作用对河道沉积粒度特征的影响起主要作用,风力作用次之.
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