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

Hodge, R. A. and 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), pp. 1597-1618. (doi:10.1002/2015JF003709)

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Abstract

Previous research into sediment cover in bedrock-alluvial channels has focussed on total 15 sediment cover, rather than the spatial distribution of cover within the channel. The latter is 16 important because it determines the bedrock areas that are protected from erosion, and the 17 start and end of sediment transport pathways. We use a 1:10 Froude-scaled model of an 18 by 18 9 m reach of a bedrock-alluvial channel to study the production and erosion of sediment 19 patches, and hence the spatial relationships between flow, bed topography and sediment 20 dynamics. The hydraulics over this bed are presented in the companion paper. In these 21 experiments specified volumes of sediment were supplied at the upstream edge of the model 22 reach as single inputs, at each of a range of discharges. This sediment formed patches and, 23 once these stabilised, flow was steadily increased to erode the patches. In summary: 1) 24 patches tend to initiate in the lowest areas of the bed, but areas of topographically-induced 25 high flow velocity can inhibit patch development; 2) at low sediment inputs the extent of 26 sediment patches is determined by the bed topography and can be insensitive to the exact 27 volume of sediment supplied; and, 3) at higher sediment inputs more extensive patches are 28 produced, stabilised by grain-grain and grain-flow interactions, and less influenced by the bed 29 topography. Bedrock topography can therefore be an important constraint on sediment patch 30 dynamics, and topographic metrics are required that incorporate its within-reach variability. 31 The magnitude and timing of sediment input events controls reach-scale sediment cover.

Item Type:Articles
Additional Information:This project was supported by the Royal Geographical Society (with IBG) with a Small Research Grant awarded to RAH.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Hoey, Professor Trevor and Hodge, Dr Rebecca
Authors: Hodge, R. A., and Hoey, T. B.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
Journal Name:Journal of Geophysical Research: Earth Surface
Publisher:Wiley-Blackwell Publishing Ltd.
ISSN:2169-9003
ISSN (Online):2169-9011
Published Online:29 July 2016
Copyright Holders:Copyright © 2016 American Geophysical Union
First Published:First published in Journal of Geophysical Research: Earth Surface 121(9): 1597-1618
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
550121Gravel-Bed Rivers ConferenceRebecca HodgeRoyal Geographical Society (ROY-GEOG)RGS-IBG 09/10SCHOOL OF GEOGRAPHICAL & EARTH SCIENCES