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Morphodynamic signatures of braiding mechanisms as expressed through change in sediment storage in a gravel-bed river

Morphodynamic signatures of braiding mechanisms as expressed through change in sediment storage in a gravel-bed river
Morphodynamic signatures of braiding mechanisms as expressed through change in sediment storage in a gravel-bed river
Previous flume-based research on braided channels has revealed four classic mechanisms that produce braiding: central bar development, chute cutoff, lobe dissection, and transverse bar conversion. The importance of these braiding mechanisms relative to other morphodynamic mechanisms in shaping braided rivers has not yet been investigated in the field. Here we exploit repeat topographic surveys of the braided River Feshie (UK) to explore the morphodynamic signatures of different mechanisms of change in sediment storage. Our results indicate that, when combined, the four classic braiding mechanisms do indeed account for the majority of volumetric change in storage in the study reach (61% total). Chute cutoff, traditionally thought of as an erosional braiding mechanism, appears to be the most common braiding mechanism in the study river, but was more the result of deposition during the construction of diagonal bars than it was the erosion of the chute. Three of the four classic mechanisms appeared to be largely net aggradational in nature, whereas secondary mechanisms (including bank erosion, channel incision, and bar sculpting) were primarily net erosional. Although the role of readily erodible banks in facilitating braiding is often conceptualized, we show that bank erosion is as or more important a mechanism in changes in sediment storage than most of the braiding mechanisms, and is the most important “secondary” mechanism (17% of total change). The results of this study provide one of the first field tests of the relative importance of braiding mechanisms observed in flume settings.
0148-0227
759-779
Wheaton, Joseph M.
0d7be603-4296-4406-a46f-814288839dc2
Brasington, James
bed2c201-e84a-461d-bcc6-4c8d952da803
Darby, Stephen E.
4c3e1c76-d404-4ff3-86f8-84e42fbb7970
Kasprak, Alan
405279e6-337a-4393-a406-ddcd46797152
Sear, D.A.
ccd892ab-a93d-4073-a11c-b8bca42ecfd3
Vericat, Damia
77694430-93dd-45eb-8706-6f9cef467f5e
Wheaton, Joseph M.
0d7be603-4296-4406-a46f-814288839dc2
Brasington, James
bed2c201-e84a-461d-bcc6-4c8d952da803
Darby, Stephen E.
4c3e1c76-d404-4ff3-86f8-84e42fbb7970
Kasprak, Alan
405279e6-337a-4393-a406-ddcd46797152
Sear, D.A.
ccd892ab-a93d-4073-a11c-b8bca42ecfd3
Vericat, Damia
77694430-93dd-45eb-8706-6f9cef467f5e

Wheaton, Joseph M., Brasington, James, Darby, Stephen E., Kasprak, Alan, Sear, D.A. and Vericat, Damia (2013) Morphodynamic signatures of braiding mechanisms as expressed through change in sediment storage in a gravel-bed river. Journal of Geophysical Research, 118 (2), 759-779. (doi:10.1002/jgrf.20060).

Record type: Article

Abstract

Previous flume-based research on braided channels has revealed four classic mechanisms that produce braiding: central bar development, chute cutoff, lobe dissection, and transverse bar conversion. The importance of these braiding mechanisms relative to other morphodynamic mechanisms in shaping braided rivers has not yet been investigated in the field. Here we exploit repeat topographic surveys of the braided River Feshie (UK) to explore the morphodynamic signatures of different mechanisms of change in sediment storage. Our results indicate that, when combined, the four classic braiding mechanisms do indeed account for the majority of volumetric change in storage in the study reach (61% total). Chute cutoff, traditionally thought of as an erosional braiding mechanism, appears to be the most common braiding mechanism in the study river, but was more the result of deposition during the construction of diagonal bars than it was the erosion of the chute. Three of the four classic mechanisms appeared to be largely net aggradational in nature, whereas secondary mechanisms (including bank erosion, channel incision, and bar sculpting) were primarily net erosional. Although the role of readily erodible banks in facilitating braiding is often conceptualized, we show that bank erosion is as or more important a mechanism in changes in sediment storage than most of the braiding mechanisms, and is the most important “secondary” mechanism (17% of total change). The results of this study provide one of the first field tests of the relative importance of braiding mechanisms observed in flume settings.

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e-pub ahead of print date: 22 May 2013
Published date: June 2013
Organisations: Geography & Environment, Earth Surface Dynamics

Identifiers

Local EPrints ID: 350462
URI: https://eprints.soton.ac.uk/id/eprint/350462
ISSN: 0148-0227
PURE UUID: be7e8ea3-2653-4b8a-9de0-a5eb9ca1f683
ORCID for Stephen E. Darby: ORCID iD orcid.org/0000-0001-8778-4394
ORCID for D.A. Sear: ORCID iD orcid.org/0000-0003-0191-6179

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Date deposited: 27 Mar 2013 12:22
Last modified: 06 Jun 2018 13:07

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Contributors

Author: Joseph M. Wheaton
Author: James Brasington
Author: Alan Kasprak
Author: D.A. Sear ORCID iD
Author: Damia Vericat

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