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Integrating suspended sediment flux in large alluvial river channels: application of a synoptic rouse-based model to the Irrawaddy and Salween rivers

Integrating suspended sediment flux in large alluvial river channels: application of a synoptic rouse-based model to the Irrawaddy and Salween rivers
Integrating suspended sediment flux in large alluvial river channels: application of a synoptic rouse-based model to the Irrawaddy and Salween rivers
A large portion of freshwater and sediment is exported to the ocean by a small number of major rivers. Many of these mega rivers are subject to substantial anthropogenic pressures, which are having a major impact on water and sediment delivery to deltaic ecosystems. Due to hydrodynamic sorting, sediment grainsize and composition vary strongly with depth and across the channel in large rivers, complicating flux quantification. To account for this, we modifed a semi-empirical Rouse model, synoptically predicting sediment concentration, grain size distribution, and organic carbon (%OC) concentration with depth and across the river channel. Using suspended sediment depth samples and flow velocity data, we applied this model to calculate sediment fluxes of the Irrawaddy (Ayeyarwady) and the Salween (Thanlwin), the last two free-flowing mega rivers in Southeast Asia. Deriving sediment discharge rating curves, we calculated an annual sediment flux of 326+91− 70Mt/year for the Irrawaddy and 159+78− 51Mt/year for the Salween, together exporting 46% as much sediment as the Ganges-Brahmaputra system. The mean flux-weighted sediment exported by the Irrawaddy is significantly coarser (D84¼ 193 ± 13 microns) and OC-poorer (0.29 ± 0.08 wt%)compared to the Salween (112 ± 27 microns and 0.59 ± 0.16 wt%, respectively). Both rivers export similar amounts of particulate organic carbon, with a total of 1:9þ1:4− 0:9Mt C/year, 53% as much as the Ganges-Brahmaputra.These results underline the global significance of the Irrawaddy and Salween rivers and warrant continued monitoring of their sediment flux, given the increasing anthropogenic pressures on these river basins
POC flux, hydrodynamic sorting, megarivers, particulate organic carbon, sediment flux, sediment transport
2169-9003
Baronas, J. Jotautas
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Stevenson, Emily I.
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Hackney, Christopher R.
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Darby, Stephen E.
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Bickle, Michael J.
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Hilton, Robert G.
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Larkin, Christina S.
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Parsons, Daniel R.
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Khaing, Aung Myo
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Tipper, Edward T.
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Baronas, J. Jotautas
9c9473d9-6376-4dc7-b940-ee6d0427ef01
Stevenson, Emily I.
d6f2e095-ee90-4acf-b9a1-66dcfeb12b7e
Hackney, Christopher R.
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Darby, Stephen E.
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Bickle, Michael J.
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Hilton, Robert G.
63b6109b-020f-4cdd-8c16-7a8137f9343a
Larkin, Christina S.
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Parsons, Daniel R.
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Khaing, Aung Myo
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Tipper, Edward T.
b966fdef-6e38-40dd-b22e-c529f4b974d0

Baronas, J. Jotautas, Stevenson, Emily I., Hackney, Christopher R., Darby, Stephen E., Bickle, Michael J., Hilton, Robert G., Larkin, Christina S., Parsons, Daniel R., Khaing, Aung Myo and Tipper, Edward T. (2020) Integrating suspended sediment flux in large alluvial river channels: application of a synoptic rouse-based model to the Irrawaddy and Salween rivers. Journal of Geophysical Research: Earth Surface, 125 (9), [e2020JF005554]. (doi:10.1029/2020JF005554).

Record type: Article

Abstract

A large portion of freshwater and sediment is exported to the ocean by a small number of major rivers. Many of these mega rivers are subject to substantial anthropogenic pressures, which are having a major impact on water and sediment delivery to deltaic ecosystems. Due to hydrodynamic sorting, sediment grainsize and composition vary strongly with depth and across the channel in large rivers, complicating flux quantification. To account for this, we modifed a semi-empirical Rouse model, synoptically predicting sediment concentration, grain size distribution, and organic carbon (%OC) concentration with depth and across the river channel. Using suspended sediment depth samples and flow velocity data, we applied this model to calculate sediment fluxes of the Irrawaddy (Ayeyarwady) and the Salween (Thanlwin), the last two free-flowing mega rivers in Southeast Asia. Deriving sediment discharge rating curves, we calculated an annual sediment flux of 326+91− 70Mt/year for the Irrawaddy and 159+78− 51Mt/year for the Salween, together exporting 46% as much sediment as the Ganges-Brahmaputra system. The mean flux-weighted sediment exported by the Irrawaddy is significantly coarser (D84¼ 193 ± 13 microns) and OC-poorer (0.29 ± 0.08 wt%)compared to the Salween (112 ± 27 microns and 0.59 ± 0.16 wt%, respectively). Both rivers export similar amounts of particulate organic carbon, with a total of 1:9þ1:4− 0:9Mt C/year, 53% as much as the Ganges-Brahmaputra.These results underline the global significance of the Irrawaddy and Salween rivers and warrant continued monitoring of their sediment flux, given the increasing anthropogenic pressures on these river basins

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More information

Accepted/In Press date: 28 July 2020
Published date: 13 August 2020
Keywords: POC flux, hydrodynamic sorting, megarivers, particulate organic carbon, sediment flux, sediment transport

Identifiers

Local EPrints ID: 444184
URI: http://eprints.soton.ac.uk/id/eprint/444184
ISSN: 2169-9003
PURE UUID: 7c74b24b-9654-43b2-85a7-f9532b801ce1
ORCID for Stephen E. Darby: ORCID iD orcid.org/0000-0001-8778-4394
ORCID for Christina S. Larkin: ORCID iD orcid.org/0000-0002-6420-0461

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Date deposited: 30 Sep 2020 16:31
Last modified: 23 Jul 2022 02:29

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Contributors

Author: J. Jotautas Baronas
Author: Emily I. Stevenson
Author: Michael J. Bickle
Author: Robert G. Hilton
Author: Christina S. Larkin ORCID iD
Author: Daniel R. Parsons
Author: Aung Myo Khaing
Author: Edward T. Tipper

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