长江源区河网密布,多数河流仍处于自然演变过程中,河谷地貌保存完整。基于实地踏勘资料,结合 SRTM3 DEM 对长江源区部分河流河谷地貌及水沙特性进行了分析。研究河流涵盖长江北源楚玛尔河、正源沱沱河、南源当曲、干流通天河及支流布曲、尕尔曲。根据河谷形态及河流地貌,可将这些河段归纳为3类:高原冲积型、丘陵坦谷型和高山峡谷型。其中:高原冲积型河道平面多呈游荡或多股分汊;丘陵坦谷型河道平面呈单一或分汊态势;高山峡谷型河道则为单一河道。研究时段内,长江源3个源头中,当曲流量最大,沱沱河流量大于楚玛尔河;输沙量则表现为沱沱河最大、楚玛尔河其次,当曲最小。泥沙分析发现:平面呈游荡状态的河流,其泥沙特征与其他河型有明显不同,具有悬移质含沙量大、粒径粗且均匀,床沙粒径较细的特点。相关分析显示河道宽度与水流含沙量呈正相关关系,初步说明了游荡河型产生的原因。

Characterized by various types of valley landscape, the source region of Yangtze River is densely covered by river networks, most of which are still in the process of natural evolution. In this paper, landform in the source region of Yangtze River is investigated based on SRTM3 DEM data of some representative river reaches, inclusive of Chumaer River, Tuotuo River, Dangqu River, Tongtian River, Buqu River, and Gaer River. Water and sediment characteristics are also analyzed from the observed data. According to the river valley shape and river landform, the river channel in the source region can be divided into three types: alluvial plateau, hilly valley, and alpine valley, among which the alluvial plateau is mostly featured by wandering or multiple branches, the hilly valley by single or branching plane form, and the alpine valley by single channel. Among the three source rivers, i.e. the south, north, and due sources, the discharge of Dangqu River (the south source) is the largest, and that of Chumaer River is the smallest; sediment discharge of Tuotuo River is the largest, followed by that of Chumaer River and Dangqu River in sequence. Moreover, suspended sediment in all the wandering river reaches, which is coarser and more uniform, is larger in amount than in straight, curved, or branched river reaches; the width of river channel is positively correlated with the sediment concentration of water flow, which preliminarily explains the causes of alluvial river formation.