Based on the river networks extracted from digital elevation models (DEMs) at 30 m resolution, combined with the remote sensing data, the hierarchical rules of the structural and morphological characteristics of the 6th–7th order river networks in the middle and upper Yellow River basin were analyzed. The results show that the river networks of the middle and upper Yellow River sub-basins present significant self-similar characteristics in the range of 1–5 orders. The middle reaches of the Yellow River sub-basins have higher bifurcation ratio (R_B=4.83), river width ratio (R_W=2.13) and average river length (L=4.80 km), while the upper reaches of the Yellow River basin have higher density (D=1.25 km⁻¹). In terms of river network structure, aridity index, soil water content and vegetation coverage are the main factors affecting the river network structure in the middle of the Yellow River sub-basins, while the river network structure in the upper reaches of the Yellow River sub-basins are more related to the average slope of the basin and soil erodibility. Further analysis of four typical sub-basins in the middle reaches of the Yellow River basin shows that although the typical sub-basins in the loess region have relatively higher sediment production capacity, their sediment transport capacities may be affected by the river network structure and channel morphology. This study reveals the role of river network structure and channel morphology as indicators of water and sediment transport characteristics, and emphasizes the necessity of differentiated river management measures for basins in the Yellow River basin with different underlying surface characteristics.

middle and upper reaches of the Yellow River, river network hierarchy, structure and morphology; underlying surface, basin factors, water-sediment effect

基于30 m水平分辨率的数字高程模型, 提取黄河中游和上游河网, 结合遥感数据, 分析黄河中上游6~7级子河网结构(分支比和河宽比)以及河道形态(河网密度和河道长度)特征的分级规律。结果表明, 中游和上游子流域河网均在1~5级范围内呈现较显著的自相似特性。其中, 黄河中游河网呈现更高的分支比(R_B=4.83)、河宽比(R_W=2.13)和平均河长(L=4.80 km), 黄河上游河网则具有更高的河网密度(D=1.25 km⁻¹)。河网结构方面, 中游子流域的河网结构主要受干燥度、土壤含水量和植被覆盖度影响, 上游子流域的河网结构则与流域平均坡度和土壤可蚀性的关系更紧密。对黄河中游4个典型子流域的进一步分析表明, 尽管黄土区典型子流域呈现相对更高的产沙能力, 但其输沙能力可能受到河网结构与河道形态的影响。研究结果揭示河网结构和河道形态对水沙输移特征具有指示作用, 并表明对不同下垫面特征流域实行差异化河流治理措施的必要性。