Impact of Late Quaternary dammed lake-outburst floods along the Yarlung Tsangpo River on the sedimentary and landscape evolution, Southern Tibet

The extreme outburst floods that have occurred within orogenic terrain on the Tibetan Plateau during the Late Quaternary are closely linked to tectonic and climatic factors. Such floods likely induced very rapid, short-term geomorphic impacts on the evolution of mountain drainage systems and patterns of sedimentary movement. We report here the discovery of multistage glacially-dammed lake outburst floods that occurred along the middle-lower reaches of the Yarlung Tsangpo River in the Himalayan orogenic belt since the Middle Pleistocene by combining comprehensive geomorphic, stratigraphic and geochronologic investigations. The differential uplift of the active north-trending rift zones and the Namche Barwa Syntaxis has resulted in localized topographic lift and the formation of river knickpoints, contributing to the development and stabilization of glacial dams. River damming and outburst events have also been influenced by glacial-interglacial climate fluctuations since the Middle Pleistocene. Based on the analysis of the knickpoint migration process, the repeated glacial dams had been effective in impeding headward river erosion during glacial periods. The focused erosion and extensive mobilization of sediment by low-frequency, high-energy floods have resulted in a repeated pattern of material transport and deposition from the Tibetan Plateau interior to its exterior. Furthermore, the dammed lake and outburst floods may have significantly impacted any downstream prehistoric human settlements.