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New evidence of high-magnitude Holocene floods in the Purlung Tsangpo River, southeastern Tibetan Plateau.

Authors :
Wang, Hao
Cui, Peng
Yang, Anna
Tang, Jinbo
Wen, Shusong
Yang, Zewen
Zhou, Liqin
Liu, Weiming
Ahmed Bazai, Nazir
Source :
CATENA. Dec2023, Vol. 233, pN.PAG-N.PAG. 1p.
Publication Year :
2023

Abstract

• New sedimentary evidences of high-magnitude floods in the Purlung Tsangpo basin. • Reconstruct the paleo-discharge of 37,000 m3/s, possibly resulting from outburst flood. • The Paleo-flood event occurred 2.2–2.6 cal kyr BP, following Holocene climate transition. Catastrophic flood events are the most devastating natural hazard in the world, and direct human observation or instrumental/systematic measurement cannot capture the full range of their frequency-magnitudes. It is essential to reconstruct large-magnitude, rare floods that are recorded in landforms and sediments. Recently, palaeohydrology studies associated with Holocene palaeofloods in Himalayan rivers have been gaining attention. Exceptional Holocene outburst floods have been invoked as a highly efficient erosion agent contributing to the rapid incision of the Tsangpo Gorge. Despite its significance, palaeoflood records upstream of Tsangpo Gorge have rarely been explored. This study presents a series of flood deposits consisting of laminated silt and sand or repeated cross-bedding sets, which points to high-magnitude flood. Inverse hydraulic modelling of the step-backwater method based on HEC-RAS software was applied to acquire the water surface profile under varying peak discharge scenarios. The discharges of palaeofloods were estimated by relating elevations of flood features to water surface profiles calculated for the reach. The result provides a minimum estimate of the peak discharge of approximately 3.70 × 104 m3/s with a maximal depth of up to 47 m. The overestimation of the peak discharge due to post-event channel incision is up to 3000 m3/s. Seven charcoal 14C dates give a narrow age range between 2.2 and 2.6 ka cal BP. This flood occurred only a few hundred years after a period of climate transition at ∼ 3 ka BP, which was prone to hydrological extremes. Since the reconstructed palaeodischarge is significantly beyond the scope of either rainfall floods or glacial lake outburst floods, it can be inferred that the breaching of an upstream landslide dam is the most reasonable origin. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
03418162
Volume :
233
Database :
Academic Search Index
Journal :
CATENA
Publication Type :
Academic Journal
Accession number :
172427436
Full Text :
https://doi.org/10.1016/j.catena.2023.107516