Bed load tracer mobility in a mixed bedrock/alluvial channel

Ferguson, R.I.; Sharma, B.P.; Hodge, R.A.; Hardy, R.J.; Warburton, J.

doi:10.1002/2016jf003946

Bed load tracer mobility in a mixed bedrock/alluvial channel

Ferguson, R.I.; Sharma, B.P.; Hodge, R.A.; Hardy, R.J.; Warburton, J.

Authors

Emeritus Professor Rob Ferguson r.i.ferguson@durham.ac.uk

B.P. Sharma

Professor Rebecca Hodge rebecca.hodge@durham.ac.uk
Professor

Professor Richard Hardy r.j.hardy@durham.ac.uk
Professor

Professor Jeff Warburton jeff.warburton@durham.ac.uk
Professor

Abstract

The presence of bare or partially-covered rock in an otherwise alluvial river implies a downstream change in transport capacity relative to supply. Field investigations of this change and what causes it are lacking. We used two sets of magnet-tagged tracer clasts to investigate bedload transport during the same sequence of floods in fully alluvial, bare rock, and partial-cover reaches of an upland stream. High-flow shear stresses in different reaches were calculated using stage loggers. Tracers seeded in the upstream alluvial channel moved more slowly than elsewhere until the frontrunners reached bare rock and sped up. Tracers seeded on bare rock moved rapidly off it and accumulated just upstream from, and later in, a partial-cover zone with many boulders. The backwater effect of the boulder-rich zone is significant in reducing tracer mobility. Tracer movement over full or partial sediment cover was size selective but dispersion over bare rock was not. Along-channel changes in tracer mobility are interpreted in terms of measured differences in shear stress and estimated differences in threshold stress.

Citation

Ferguson, R., Sharma, B., Hodge, R., Hardy, R., & Warburton, J. (2017). Bed load tracer mobility in a mixed bedrock/alluvial channel. Journal of Geophysical Research: Earth Surface, 122(4), 807-822. https://doi.org/10.1002/2016jf003946

Journal Article Type	Article
Acceptance Date	Mar 4, 2017
Online Publication Date	Apr 6, 2017
Publication Date	Apr 6, 2017
Deposit Date	Apr 5, 2017
Publicly Available Date	Oct 6, 2017
Journal	Journal of Geophysical Research: Earth Surface
Print ISSN	2169-9011
Publisher	American Geophysical Union
Peer Reviewed	Peer Reviewed
Volume	122
Issue	4
Pages	807-822
DOI	https://doi.org/10.1002/2016jf003946

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Copyright Statement
R. I. Ferguson, B. P. Sharma, R. A. Hodge, R. J. Hardy and J. Warburton (2017), Bedload tracer mobility in a mixed bedrock/alluvial channel, Journal of Geophysical Research: Earth Surface, 122(4), 807-822, 10.1002/2016jf003946 (DOI). To view the published open abstract, go to https://doi.org/ and enter the DOI.