Improving predictions of critical shear stress in gravel bed rivers: Identifying the onset of sediment transport and quantifying sediment structure

Hodge, Rebecca A.; Voepel, Hal E.; Yager, Elowyn M.; Leyland, Julian; Johnson, Joel P. L.; Sear, David A.; Ahmed, Sharif

Abstract

Understanding when gravel moves in river beds is essential for a range of different applications but is still surprisingly hard to predict. Here we consider how our ability to predict critical shear stress (τ c ) is being improved by recent advances in two areas: (1) identifying the onset of bedload transport; and (2) quantifying grain‐scale gravel bed structure. This paper addresses these areas through both an in‐depth review and a comparison of new datasets of gravel structure collected using three different methods. We focus on advances in these two areas because of the need to understand how the conditions for sediment entrainment vary spatially and temporally, and because spatial and temporal changes in grain‐scale structure are likely to be a major driver of changes in τ c . We use data collected from a small gravel‐bed stream using direct field‐based measurements, terrestrial laser scanning (TLS) and computed tomography (CT) scanning, which is the first time that these methods have been directly compared. Using each method, we measure structure‐relevant metrics including grain size distribution, grain protrusion and fine matrix content. We find that all three methods produce consistent measures of grain size, but that there is less agreement between measurements of grain protrusion and fine matrix content.

Citation

Hodge, R. A., Voepel, H. E., Yager, E. M., Leyland, J., Johnson, J. P. L., Sear, D. A., & Ahmed, S. (2024). Improving predictions of critical shear stress in gravel bed rivers: Identifying the onset of sediment transport and quantifying sediment structure. Earth Surface Processes and Landforms, 49(8), 2517-2537. https://doi.org/10.1002/esp.5842

• Journal Article Type: Article
• Acceptance Date: Mar 25, 2024
• Online Publication Date: Apr 18, 2024
• Publication Date: Jun 30, 2024
• Deposit Date: Apr 22, 2024
• Publicly Available Date: Apr 24, 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: 49
• Issue: 8
• Pages: 2517-2537
• DOI: https://doi.org/10.1002/esp.5842
• Keywords: terrestrial laser scanning, computed tomography scanning, critical shear stress, gravel bed rivers, bedload transport
• Public URL: https://durham-repository.worktribe.com/output/2389898