Hyperconcentrated floods cause extreme gravel transport through the sandy rivers of the Gangetic Plains

Quick, L. , Creed, M. J. , Sinclair, H. D., Attal, M., Borthwick, A. G. L. and Sinha, R. (2023) Hyperconcentrated floods cause extreme gravel transport through the sandy rivers of the Gangetic Plains. Communications Earth and Environment, 4, 297. (doi: 10.1038/s43247-023-00953-9)

Abstract

The Gangetic Plains comprise steep gravelly river channels that transition to low gradient sandy channels 10-40 km downstream of the mountain front. This “gravel-sand transition" is characterized by an abrupt greater-than-one-order-of-magnitude drop in both gradient and sediment grain size, suggesting a degree of long-term stability. However, the stratigraphic record of the gravel-sand transition in the Miocene Siwalik Group demonstrates intermittent transport of coarse gravels tens of kilometres downstream of the transition; such events in contemporary channels would drive channel avulsion(s) and increase flood risk, devastating communities across the plains. We combine sedimentological analysis of Siwalik deposits with entrainment calculations which demonstrate that hyperconcentration is required to transport coarse bedload over low-gradient plains. Transport conditions are attainable when intense monsoon precipitation (a 200- to 1000-year event) is combined with increased suspended sediment concentrations in channels. Predicted climate change and ongoing seismicity increase the likelihood of such extreme events within this century.

• Item Type: Articles
• Additional Information: This study formed part of a Natural Environment Research Council (NERC) funded E3 DTP Ph.D. (NE/L002558/1).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Quick, Dr Laura and Creed, Dr Maggie
• Authors: Quick, L., Creed, M. J., Sinclair, H. D., Attal, M., Borthwick, A. G. L., and Sinha, R.
• College/School: College of Science and Engineering > School of Engineering > Infrastructure and Environment; College of Science and Engineering > School of Geographical and Earth Sciences
• Journal Name: Communications Earth and Environment
• Publisher: Nature Research
• ISSN: 2662-4435
• ISSN (Online): 2662-4435
• Published Online: 23 August 2023
• Copyright Holders: Copyright © The Author(s) 2023
• First Published: First published in Communications Earth and Environment 4:297
• Publisher Policy: Reproduced under a Creative Commons license