Author(s): Du Jun; Wang Zhaoyin; Li Zhiwei; Han Lujie
Linked Author(s): Zhiwei Li
Keywords: Qinghai-Tibet Plateau; Yellow River source; Xinghai-Tongde Basin; Spinulose stream network
Abstract: Based on field investigation and measurement, remote sensing interpretation and DEM geomorphic feature extraction, this paper introduced the spinulose stream networks, a unique drainage pattern found in the Xinghai-Tongde Basin in the source of the Yellow River. It is a stream network formed in flat broad valleys covered by deep fluvial sediments and lacustrine sediments where a series of straight and short tributaries in a nearly parallel line motivated by tectonic uplift and retrogressive erosion of running water deeply downcut mainstreams. The main morphological characteristics of spinulose stream network patterns are: firstly, lengths of the tributaries are short and no sub-stream developed. Hence, the flow confluence areas are all very small, which makes the tributaries as a kind of seasonal rivers; secondly, spinulose tributaries' average converging angle is about 74°and they merge into mainstreams in parallel; thirdly, most spinulose tributaries emerge in middle and lower reaches of mainstreams with large elevation difference on riverbeds in converging entrances between tributaries and mainstreams, e.g. 15 m in average; fourthly, most tributaries' longitudinal profiles are convex or concave-convex, which indicates the channels are far from equilibrium and still have the potential be eroded. The preliminary study suggested that two preconditions are needed for development of spinulose stream network. One is gentle valley or basin covered by deep sediments, the other is high elevation difference between the meeting point of mainstream and tributaries because of rapid and deep incision of mainstream. As the mainstream and tributaries of the Yellow River downcut the Xinghai-Tongde Basin rapidly owing to plateau uplift and erodible sediments, young branch channels gain a rapid development from retrogressive erosion at first. However, afterwards, with the increasing elevation difference of riverbeds in converging entrances of mainstreams and tributaries, tributaries cannot gain adequate retrogressive wash. Furthermore, the basins they develop are relatively flat unable to gather more water flow. Finally, there comes the spinulose stream network.
Year: 2012