@article{3d06f4a085d947a68dfd707ca5e9e7b8,
title = "Rapid fluvial remobilization of sediments deposited by the 2021 Chamoli disaster, Indian Himalaya",
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.",
author = "Westoby, {Matthew J.} and Dunning, {Stuart A.} and Carrivick, {Jonathan L.} and Coulthard, {Thomas J.} and Kalachand Sain and Amit Kumar and Etienne Berthier and Haritashya, {Umesh K.} and Shean, {David E.} and Azam, {Mohd. Farooq} and Kavita Upadhyay and Michele Koppes and Mccourt, {Harley R.} and Shugar, {Dan H.}",
note = "Funding information: Data involved in this research are in the process of being archived by the UKRI Environmental Information Data Centre and in the interim are available from the corresponding author on request. Westoby, Coulthard, Dunning, and Carrivick acknowledge support via the UK Natural Environment Research Council grant NE/W002930/1. Westoby and Berthier acknowledge DINAMIS/Centre National d{\textquoteright}{\'E}tudes Spatiales (France) for facilitating the acquisition of Pl{\'e}iades imagery. Shugar acknowledges Natural Sciences and Engineering Research Council of Canada (DG2020-0407) and Alberta Innovates. Shean and Haritashya respectively acknowledge support via NASA High-Mountain Asia grants 80NSSC20K1595 and 80NSSC19K0653, and Haritashya also acknowledges NASA Interdisciplinary Research in Earth Science grant 80NSSC18K0432 and the University of Dayton{\textquoteright}s Mann Endowed Chair in the Sciences. Sain acknowledges support from the J.C. Bose National Fellowship program (SERB-DST, New Delhi). We thank Planet Labs (San Francisco, USA) for provision of satellite data, and Shashank Bhushan for assistance with DEM generation. The authors thank the three anonymous reviewers whose comments helped to improve the manuscript.",
year = "2023",
month = oct,
day = "1",
doi = "10.1130/G51225.1",
language = "English",
volume = "51",
pages = "924–928",
journal = "Geology",
issn = "0091-7613",
publisher = "Geological Society of America",
number = "10",
}
