Formation of meandering streams in a young floodplain within the Yarlung Tsangpo Grand Canyon in the Tibetan Plateau

Abstract

A recent discovery of two unique meandering streams near the Yarlung Tsangpo Grand Canyon facilitates the present study. Given the contrasting channel patterns compared with the surrounding bedrock and braided reaches, as well as their recent formation due to dam-induced topographic changes within the valley, this study offers critical insights into the formation and evolution processes of meandering channels. It is found that, first, the prolonged sedimentation process due to the backwater of the mainstream of the floodplain proves a material base for the formation of the meandering river. Proper bank strength provided by the floodplain (stratified layer of root-soil composite and silty clay) contrasts the stream from a braided pattern into a single-threaded pattern, then the alternate bar in the upstream preludes the meandering channel formation. The annual migration rate of the stream is consistent with other large-scale natural meandering rivers. Congruences and disparities with the analytical meandering migration model of the present stream (that the meandering path follows the Kinoshita curve with noticeable flatness but no skewness) highlight the complex interplay of local factors in shaping meandering processes, offering valuable insights into both the unique characteristics of the Cuoka streams and the broader principles governing meander formation.