长江源区河流的河网形态和辫状河型独具特色.基于SRTM3 DEM、Landsat 4-5 TM遥感影像和Google Earth卫星影像数据提取长江源区22条河流纵剖面,利用简单数学函数拟合纵剖面形态,并结合Hack剖面、凹曲指数及河长坡降SL指标等参数分析河流纵剖面的发育与构造活动之间的内在关系.研究表明:长江源区大部分河流纵剖面的最佳拟合形态为指数函数(R2≥0.99),间接地说明该区域河流侵蚀作用较强.这22条支流的凹度值约为1.0,其中当曲的凹曲度最大,色吾曲最小,属于高凹曲度和极端凹曲度值.在各河流形态的统计结果中,三大源流Hack剖面均为曲线,沱沱河—通天河、当曲、楚玛尔河分别出现了8次、4次、3次宽窄交替的藕节状形态,其中宽谷段为辫状河段,窄段为峡谷限制段,标准河流坡降指数SL/K值介于2～10之间,表示河流发育处于微陡河段,地区构造活动较强.不考虑气候和基岩性质影响因素,可推测晚更新世以来新构造运动在长江源河流纵剖面演变中起主导作用.%The geometrical morphology of river network and braided rivers in the source region of Yangtze River is unique and distinctive. In this study, the longitudinal profiles of 22 rivers in the source region of the Yangtze River were extracted which were based on SRTM3 DEM (resolution 90 m) , the Landsat 4-5 TM remote sensing image, and Google Earth satellite imagery data, and a simple mathematical function (linear, exponential, logarithmic, and power function) was used to fit the longitudinal profiles, and the internal relationship between tectonic activity and development of different river longitudinal profile was analyzed based on the Hack profile, concavity index, and river slope parameter SL index etc. The results showed that the best fitting shape of the most river longitudinal profile in the source region of Yangtze River was exponential function (R2≥0.99), which confirmed that the riverbed erosion was much strong in this area indirectly. The concavity index value of the 22 branches were about 1.0, which Dangqu River was the largest, and Sewuqu River was the lowest. Thus, the concavity index corresponded to the morphological characteristics of the longitudinal profile of the river, belonging to the high and extreme value. In the statistical results of the river morphology, all Hack profiles of the three sources were curves and the Tuotuo-Tongtian River, Dangqu River and Chumaer River were respectively appeared 8 times, 4 times, and 3 times of the torose form with alternate width where the broad valley was the braided river and the canyon was confined section. The standard river slope index SL/K was between 2 ～10, indicating that the river was in the steep river and the tectonic activity was strong. Except the influence of climate change and bedrock properties, the new tectonic movement had played a leading role in the longitudinal profile evolution of the Yangtze River since the late Pleistocene.
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