EGU25-11090, updated on 27 Mar 2025
https://doi.org/10.5194/egusphere-egu25-11090
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
A field-based protocol to approximate variability in critical Shields coarse-bed rivers at the patch scale
Daniel Vázquez-Tarrío1, Estrella Carrero-Carralero2, Raúl López2, Fanny Ville2, Damià Vericat2,3, and Ramon J. Batalla2,4
Daniel Vázquez-Tarrío et al.
  • 1Department of Geo-Hazards & Climate Change, IGME, CSIC, Madrid, Spain (d.vazqueztarrio@igme.es)
  • 2Fluvial Dynamics Research Group (RIUS), University of Lleida, Lleida, Spain
  • 3Forest Science and Technology Centre of Catalonia (CTFC), Solsona, Spain
  • 4Catalan Institute for Water Research (ICRA), Girona, Spain

Predicting the flow conditions required to entrain sediment in gravel-bed rivers is essential for many issues, such as river ecology, flood risk assessment, river restoration and sustainable river management, among many others. In this regard, the critical Shields parameter is the most commonly used metric to characterise particle entrainment in bedload transport studies. Consequently, the determination of critical Shields is fundamental to the prediction of bedload transport in gravel-bed rivers. Conventional field studies have focused on estimating a reach-averaged Shields stress, despite the large spatial variability that this parameter exhibits at the reach scale. This is largely due to the lack of standardised field approaches for characterising Shields stress in a spatially distributed manner. In this work, we propose a field-based procedure for estimating the frequency distribution of critical Shields at the patch scale in a gravel-bed river, based on the measurement of resistance to movement of individual clasts and a number of variables related to the position and orientation of grains. Following this procedure, we have approximated the patch-scale variability of particle entrainment conditions in a gravel bar of the Upper Cinca River, located in the southern watershed of the Pyrenees. The results (mean Shields ~0.03) are consistent with previous estimates of critical Shields in this river and with established theory of particle entrainment in gravel-bed rivers. We believe that this method has great potential to provide valuable field information on particle entrainment.

Ackowledgements: This research benefitted from the methods and outcomes of the MorphHab research project (PID2019-104979RB-I00/AEI/10.13039/501100011033, Ministry of Science, Innovation and Universities (MICINN), Government of Spain). The work by the first author is also part of the 2023–2026 grant signed between the Spanish Directorate General for Water (DGA-MITERD; Government of Spain) and the Spanish National Research Council (CSIC-Ministry of Science, Innovation and Universities), which includes action “Sedimentary Morphodynamics” (20233TE012: IGME-CSIC; Tarquín 2 Project).

How to cite: Vázquez-Tarrío, D., Carrero-Carralero, E., López, R., Ville, F., Vericat, D., and Batalla, R. J.: A field-based protocol to approximate variability in critical Shields coarse-bed rivers at the patch scale, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11090, https://doi.org/10.5194/egusphere-egu25-11090, 2025.