Premium
Integrating Suspended Sediment Flux in Large Alluvial River Channels: Application of a Synoptic Rouse‐Based Model to the Irrawaddy and Salween Rivers
Author(s) -
Baronas J. Jotautas,
Stevenson Emily I.,
Hackney Christopher R.,
Darby Stephen E.,
Bickle Michael J.,
Hilton Robert G.,
Larkin Christina S.,
Parsons Daniel R.,
Myo Khaing Aung,
Tipper Edward T.
Publication year - 2020
Publication title -
journal of geophysical research: earth surface
Language(s) - English
Resource type - Journals
eISSN - 2169-9011
pISSN - 2169-9003
DOI - 10.1029/2020jf005554
Subject(s) - sediment , flux (metallurgy) , sorting , hydrology (agriculture) , environmental science , sediment transport , total organic carbon , geology , drainage basin , geomorphology , geography , environmental chemistry , materials science , geotechnical engineering , cartography , computer science , metallurgy , programming language , chemistry
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 32 6 − 70 + 91Mt/year for the Irrawaddy and 15 9 − 51 + 78Mt/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 ( D 84 = 193 ± 13 μ m) and OC‐poorer ( 0.29 ± 0.08 wt%) compared to the Salween ( 112 ± 27 μ m and 0.59 ± 0.16 wt%, respectively). Both rivers export similar amounts of particulate organic carbon, with a total of 1 . 9 − 0 . 9 + 1 . 4Mt 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.