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A Froude-scaled model of a bedrock-alluvial channel reach: 2. Sediment cover

Hodge, R.A.; Hoey, T.B.

A Froude-scaled model of a bedrock-alluvial channel reach: 2. Sediment cover Thumbnail


Authors

T.B. Hoey



Abstract

Previous research into sediment cover in bedrock-alluvial channels has focussed on total sediment cover, rather than the spatial distribution of cover within the channel. The latter is important because it determines the bedrock areas that are protected from erosion and the start and end of sediment transport pathways. We use a 1:10 Froude-scaled model of an 18 by 9 m reach of a bedrock-alluvial channel to study the production and erosion of sediment patches and hence the spatial relationships between flow, bed topography, and sediment dynamics. The hydraulic data from this bed are presented in the companion paper. In these experiments specified volumes of sediment were supplied at the upstream edge of the model reach as single inputs, at each of a range of discharges. This sediment formed patches, and once these stabilized, flow was steadily increased to erode the patches. In summary: (1) patches tend to initiate in the lowest areas of the bed, but areas of topographically induced high flow velocity can inhibit patch development; (2) at low sediment inputs the extent of sediment patches is determined by the bed topography and can be insensitive to the exact volume of sediment supplied; and (3) at higher sediment inputs more extensive patches are produced, stabilized by grain-grain and grain-flow interactions and less influenced by the bed topography. Bedrock topography can therefore be an important constraint on sediment patch dynamics, and topographic metrics are required that incorporate its within-reach variability. The magnitude and timing of sediment input events controls reach-scale sediment cover.

Citation

Hodge, R., & Hoey, T. (2016). A Froude-scaled model of a bedrock-alluvial channel reach: 2. Sediment cover. Journal of Geophysical Research: Earth Surface, 121(9), 1597-1618. https://doi.org/10.1002/2015jf003709

Journal Article Type Article
Acceptance Date Jul 23, 2016
Online Publication Date Sep 16, 2016
Publication Date Sep 16, 2016
Deposit Date Aug 4, 2016
Publicly Available Date Mar 16, 2017
Journal Journal of Geophysical Research: Earth Surface
Print ISSN 2169-9011
Electronic ISSN 2169-9011
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 121
Issue 9
Pages 1597-1618
DOI https://doi.org/10.1002/2015jf003709
Public URL https://durham-repository.worktribe.com/output/1399703

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Copyright Statement
Advance online version Hodge, R.A. & Hoey, T.B. (2016). A Froude-scaled model of a bedrock-alluvial channel reach: 2. Sediment cover. Journal of Geophysical Research: Earth Surface, 121(9): 1597-1618, doi: 10.1002/2015jf003709. To view the published open abstract, go to https://doi.org/ and enter the DOI.






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