Skip to main content

Research Repository

Advanced Search

Flow resistance and hydraulic geometry in bedrock rivers with multiple roughness length scales

Ferguson, R.; Hardy, R.; Hodge, R.

Flow resistance and hydraulic geometry in bedrock rivers with multiple roughness length scales Thumbnail


Authors



Abstract

Many models of incision by bedrock rivers predict water depth and shear stress from discharge; conversely, palaeoflood discharge is sometimes reconstructed from flow depth markers in rock gorges. In both cases assumptions are made about flow resistance. The depth‐discharge relation in a bedrock river must depend on at least two roughness length scales (exposed rock and sediment cover) and possibly a third (sidewalls). A conceptually attractive way to model the depth‐discharge relation in such situations is to partition the total shear stress and friction factor, but it is not obvious how to quantify the friction factor for rough walls in a way that can be used in incision process models. We show that a single flow resistance calculation using a spatially‐averaged roughness length scale closely approximates the partitioning of stress between sediment and rock, and between bed and walls, in idealised scenarios. Both approaches give closer fits to the measured depth‐discharge relations in two small bedrock reaches than can be achieved using a fixed value of Manning's n or the Chézy friction factor. Sidewalls that are substantially rougher or smoother than the bed have a significant effect on the partitioning of shear stress between bed and sidewalls. More research is needed on how best to estimate roughness length scales from observable or measurable channel characteristics.

Citation

Ferguson, R., Hardy, R., & Hodge, R. (2019). Flow resistance and hydraulic geometry in bedrock rivers with multiple roughness length scales. Earth Surface Processes and Landforms, 44(12), 2437-2449. https://doi.org/10.1002/esp.4673

Journal Article Type Article
Acceptance Date May 20, 2019
Online Publication Date May 25, 2019
Publication Date Sep 30, 2019
Deposit Date May 21, 2019
Publicly Available Date Mar 28, 2024
Journal Earth Surface Processes and Landforms
Print ISSN 0197-9337
Electronic ISSN 1096-9837
Publisher British Society for Geomorphology
Peer Reviewed Peer Reviewed
Volume 44
Issue 12
Pages 2437-2449
DOI https://doi.org/10.1002/esp.4673

Files


Published Journal Article (2 Mb)
PDF

Copyright Statement
This is the accepted version of the following article: Ferguson, R., Hardy, R. & Hodge, R. (2019). Flow resistance and hydraulic geometry in bedrock rivers with multiple roughness length scales. Earth Surface Processes and Landforms 44(12): 2437-2449 which has been published in final form at https://doi.org/10.1002/esp.4673. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.





You might also like



Downloadable Citations