University of Leicester
Browse
Cooper_et_al-2018-Earth_Surface_Processes_and_Landforms.pdf (983.82 kB)

Does the permeability of gravel river beds affect near-bed hydrodynamics?

Download (983.82 kB)
journal contribution
posted on 2018-05-01, 15:45 authored by James R. Cooper, Annie Ockleford, Stephen P. Rice, D. Mark Powell
The permeability of river beds is an important control on hyporheic flow and the movement of fine sediment and solutes into and out of the bed. However, relatively little is known about the effect of bed permeability on overlying near-bed flow dynamics, and thus on fluid advection at the sediment–water interface. This study provides the first quantification of this effect for water-worked gravel beds. Laboratory experiments in a recirculating flume revealed that flows over permeable beds exhibit fundamental differences compared with flows over impermeable beds of the same topography. The turbulence over permeable beds is less intense, more organised and more efficient at momentum transfer because eddies are more coherent. Furthermore, turbulent kinetic energy is lower, meaning that less energy is extracted from the mean flow by this turbulence. Consequently, the double-averaged velocity is higher and the bulk flow resistance is lower over permeable beds, and there is a difference in how momentum is conveyed from the overlying flow to the bed surface. The main implications of these results are three-fold. First, local pressure gradients, and therefore rates of material transport, across the sediment–water interface are likely to differ between impermeable and permeable beds. Second, near-bed and hyporheic flows are unlikely to be adequately predicted by numerical models that represent the bed as an impermeable boundary. Third, more sophisticated flow resistance models are required for coarse-grained rivers that consider not only the bed surface but also the underlying permeable structure. Overall, our results suggest that the effects of bed permeability have critical implications for hyporheic exchange, fluvial sediment dynamics and benthic habitat availability. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

History

Citation

Earth Surface Processes and Landforms, 2018, 43 (5), pp. 943-955

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/School of Geography, Geology and the Environment/Physical Geography

Version

  • VoR (Version of Record)

Published in

Earth Surface Processes and Landforms

Publisher

Wiley for British Society for Geomorphology

issn

0197-9337

eissn

1096-9837

Acceptance date

2017-09-11

Copyright date

2017

Available date

2018-05-01

Publisher version

https://onlinelibrary.wiley.com/doi/abs/10.1002/esp.4260

Language

en

Usage metrics

    University of Leicester Publications

    Categories

    Keywords

    Licence

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC