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Mud in rivers transported as flocculated and suspended bed material

Lamb, Michael P. and de Leeuw, Jan and Fischer, Woodward W. and Moodie, Andrew J. and Venditti, Jeremy G. and Nittrouer, Jeffrey A. and Haught, Daniel and Parker, Gary (2020) Mud in rivers transported as flocculated and suspended bed material. Nature Geoscience, 13 (8). pp. 566-570. ISSN 1752-0894. https://resolver.caltech.edu/CaltechAUTHORS:20200512-113619296

[img] Image (JPEG) (Extended Data Fig. 1: Mud abundances in sand-bedded rivers) - Supplemental Material
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Abstract

Riverine transport of silt and clay particles—or mud—builds continental landscapes and dominates the fluxes of sediment and organic carbon across Earth’s surface. Compared with fluxes of sand-sized grains, mud fluxes are difficult to predict. Yet, understanding the fate of muddy river sediment is fundamental to the global carbon cycle, coastal landscape resilience to sea-level rise, river restoration and river–floodplain morphodynamics on Earth and Mars. Mechanistic theories exist for suspended sand transport, but mud in rivers is often thought to constitute washload—sediment with settling velocities so slow that it does not interact with the bed, such that it depends only on upstream supply and is impossible to predict from local hydraulics. To test this hypothesis, we compiled sediment concentration profiles from the literature from eight rivers and used an inversion technique to determine settling rates of suspended mud. We found that mud in rivers is largely flocculated in aggregates that have near-constant settling velocities, independent of grain size, of approximately 0.34 mm s⁻¹, which is 100-fold faster than rates for individual particles. Our findings indicate that flocculated mud is part of suspended bed-material load, not washload, and thus can be physically described by bed-material entrainment theory.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1038/s41561-020-0602-5DOIArticle
https://rdcu.be/b5r6sPublisherFree ReadCube access
ORCID:
AuthorORCID
Lamb, Michael P.0000-0002-5701-0504
Fischer, Woodward W.0000-0002-8836-3054
Moodie, Andrew J.0000-0002-6745-036X
Venditti, Jeremy G.0000-0002-2876-4251
Nittrouer, Jeffrey A.0000-0002-4762-0157
Haught, Daniel0000-0002-8923-1512
Parker, Gary0000-0001-5973-5296
Alternate Title:Mud in rivers transported as flocculated, suspended bed-material
Additional Information:© 2020 Nature Publishing Group. Received 11 December 2019; Accepted 22 May 2020; Published 06 July 2020. This research was sponsored by a National Science Foundation grant (number EAR 1427262) to M.P.L., J.A.N. and G.P., and a Caltech Discovery grant to M.P.L. and W.W.F. Data availability: All data used in the study are previously published (Extended Data Table 1) and available in de Leeuw et al.(20). Author Contributions: M.P.L., W.W.F. and G.P. designed the study. M.P.L. and J.d.L. analysed data. A.J.M., J.G.V., J.A.N. and D.H. contributed data. M.P.L. led the writing of the manuscript with contributions from all authors. The authors declare no competing interests.
Funders:
Funding AgencyGrant Number
NSFEAR-1427262
Caltech Discovery FundUNSPECIFIED
Subject Keywords:Geomorphology; Hydrology; Sedimentology
Issue or Number:8
Record Number:CaltechAUTHORS:20200512-113619296
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200512-113619296
Official Citation:Lamb, M.P., de Leeuw, J., Fischer, W.W. et al. Mud in rivers transported as flocculated and suspended bed material. Nat. Geosci. 13, 566–570 (2020). https://doi.org/10.1038/s41561-020-0602-5
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103138
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:06 Jul 2020 17:39
Last Modified:30 Jul 2020 20:02

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