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Rapid fluvial remobilization of sediments deposited by the 2021 Chamoli disaster, Indian Himalaya

Lookup NU author(s): Dr Stuart DunningORCiD, Harley McCourt

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

High-magnitude mass flows can have a pervasive geomorphological legacy, yet the short-term response of valley floors to such intense disturbances is poorly known and poses significant observational challenges in unstable landscapes. We combined satellite remote sensing, numerical modeling, and field observations to reconstruct the short-term geomorphological response of river channels directly affected by the 7 February 2021 ice-rock avalanche−debris flow in Chamoli district, Uttarakhand, India. The flow deposited 10.4 ± 1.6 Mm3 of sediment within the first 30 km and in places reset the channel floor to a zero-state condition, requiring complete fluvial re-establishment. In the 12 months post-event, 7.0 ± 1.5 Mm3 (67.2%) of the deposit volume was removed along a 30-km-long domain and the median erosion rate was 2.3 ± 1.1 m a−1. Most sediment was removed by pre-monsoon and monsoon river flows, which conveyed bedload waves traveling at 0.1−0.3 km day−1 and sustained order-of-magnitude increases in suspended sediment concentrations as far as 85 km from the event source. Our findings characterize a high-mountain fluvial cascade with a short relaxation time and high resilience to a high-magnitude geomorphological perturbation. This system response has wider implications, notably for water quality and downstream hydropower projects, which may be disrupted by elevated bedload and suspended sediment transport.


Publication metadata

Author(s): Westoby MJ, Dunning SA, Carrivick JL, Coulthard TJ, Sain K, Kumar A, Berthier E, Haritashya UK, Shean DE, Azam MF, Upadhyay K, Koppes M, McCourt HR, Shugar DH

Publication type: Article

Publication status: Published

Journal: Geology

Year: 2023

Online publication date: 27/07/2023

Acceptance date: 13/07/2023

Date deposited: 28/07/2023

ISSN (print): 0091-7613

ISSN (electronic): 1943-2682

Publisher: Geological Society of America

URL: https://doi.org/10.1130/G51225.1

DOI: 10.1130/G51225.1


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Funding

Funder referenceFunder name
NE/W002930/1

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