Integrating Suspended Sediment Flux in Large Alluvial River Channels: Application of a Synoptic Rouse‐Based Model to the Irrawaddy and Salween Rivers

Baronas, J. Jotautas and Stevenson, Emily I. and Hackney, Christopher R. and Darby, Stephen E. and Bickle, Michael J. and Hilton, Robert G. and Larkin, Christina S. and Parsons, Daniel R. and Myo Khaing, Aung 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). ISSN 2169-9003 DOI https://doi.org/10.1029/2020JF005554

[img] Text
2020JF005554.pdf - Published Version
Available under License Creative Commons Attribution.

Download (7MB)
Official URL: https://doi.org/10.1029/2020JF005554

Abstract

A large portion of freshwater and sediment is exported to the ocean by a small number of major rivers. Many of these megarivers 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 grain size and composition vary strongly with depth and across the channel in large rivers, complicating flux quantification. To account for this, we modified 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 megarivers in Southeast Asia. Deriving sediment‐discharge rating curves, we calculated an annual sediment flux of urn:x-wiley:jgrf:media:jgrf21236:jgrf21236-math-0001 Mt/year for the Irrawaddy and urn:x-wiley:jgrf:media:jgrf21236:jgrf21236-math-0002 Mt/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 (D84 = 193 ± 13 μm) and OC‐poorer (0.29 ± 0.08 wt%) compared to the Salween (112 ± 27 μm and 0.59 ± 0.16 wt%, respectively). Both rivers export similar amounts of particulate organic carbon, with a total of urn:x-wiley:jgrf:media:jgrf21236:jgrf21236-math-0003 Mt 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.

Item Type: Article
Uncontrolled Keywords: 2020AREP; IA76
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
07 - Gold Open Access
12 - PhD
Journal or Publication Title: Journal of Geophysical Research: Earth Surface
Volume: 125
Identification Number: https://doi.org/10.1029/2020JF005554
Depositing User: Sarah Humbert
Date Deposited: 25 Sep 2020 18:32
Last Modified: 25 Sep 2020 18:32
URI: http://eprints.esc.cam.ac.uk/id/eprint/4885

Actions (login required)

View Item View Item

About cookies