A Preliminary Study on Spinulose Stream Networks in the Tongde Basin of the Yellow River Source, China

Based on field work, remote sensing interpretation and DEM geomorphic analysis, this paper introduces a unique stream networks found in the Tongde Basin within the Yellow River source. The stream networks, named spinulose stream networks for its tiny branches, was developed in flat broad valleys covered by deep fluvial sediments and loess where a series of narrow and short branches merge into deeply incised mainstream in parallel at nearly right angles. Spinulose branches, simple ordering river structure and asynchronous development of mainstream and tributaries are the three features making this kind of stream networks different from others. This preliminary study suggests that two preconditions are needed for the development of spinulose stream networks. One is gentle valley or basin covered by deep loess and sediments, the other is adequate retrogressive erosion caused by deep incision of mainstream. Historically, ancient Tongde area became a fault basin and received great amount of fluvial sediments and loess because of the uneven uplift of Tibetan Plateau. However, with the ancient Yellow River incising through the Longyangxia Gorge and connecting with inner stream networks owing to the sustained plateau uplift since the Gonghe movement, the sedimentary basin was transformed into easily erosion area where inner rivers incised rapidly. Gradually, the spinulose stream networks formed.