River reversal of the Parlung River at Songzong Town in the eastern Himalayan Syntaxis, Tibetan Plateau

Abstract

Revealing reorganization patterns of major rivers and their drainage basins have great implications for understanding evolution of mountainous landforms. Drainage reversal, as an important river process, has been widely considered to be directly associated with stream capture highlighting river erosion. As such, few study reported any other mechanisms for explaining formation of drainage reversal. However, its mechanism still remains open due to infrequent occurrence or lacking clear field evidence. Here, we first show that glacial damming highlighting river aggradation can also induce river reversal. Based on geomorphic analysis, measurements of terrace cobbles, and dating results, we suggest that two river reversals occurred at Songzong along the Parlung River in the south‐eastern region of the Tibetan Plateau. Specifically, the river reversed eastward due to a glacier damming event prior to ~23.7 ± 2.0 ka BP and then reversed to flow westward at 20.4 ± 2.7 ka BP due to the break of the glacier dam. Moreover, all the reaches upstream of the glacier deposits along the two rivers at Songzong have smaller channel steepness compared with the corresponding segments downstream, indicating that glacier deposits significantly influenced river incision process of the Parlung River. Combined with previous studies, our results may indicate that glaciers might be an important factor to influence river evolution and fluvial landform of the Eastern Himalayan Syntaxis of the Tibetan Plateau.