Flexible barrier and flow-driven woody debris: an experimental investigation of their interaction

Abstract

Flexible barriers have been recently proposed as a promising alternative for trapping woody debris driven by the flow in torrents and rivers before they reach elements at risks. Small-scale experiments in similitude with the real-scale have been conducted in view of addressing the interaction between the flow and the barrier. A particular attention was paid to the identification of the parameters with influence on the loading experienced by the barrier, varying the woody debris mixtures characteristics, water discharge, flume inclination and woody debris supply mode. This investigation emphasised the intricacy of the relation between the barrier loading and the characteristics of the trapped logs and of the logs accumulation. The barrier loading revealed inversely proportional to the woody debris accumulation permittivity, which quantifies its capacity to let the water seep through. Permittivity depended on the way the accumulation built up and on the evolution of its characteristics with increasing discharge and trapped logs volume. Finally, the loading exerted by the flow on the barrier was derived from the barrier elongation, revealing that it could be modelled as a hydrostatic load with a reduction factor of 0.5.

Keywords:

• driftwood
• flood
• flexible barrier
• flume experiment
• loading

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Acknowledgements

The authors would like to thank Ana-Rocio CERON-MAYO who performed the experiments and contributed to the previous analysis, Hervé BELLOT and Alexis BUFFET for their help in designing the experimental set up and two anonymous reviewers for providing helpful comments on a previous version of this article.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

All data generated or used during the study are available in a repository online in accordance with funder data retention policies: FilTor: Interaction between flexible barriers and flows (INRAE), https://data.inrae.fr/dataverse/filtor, backwater rise and LW releases: https://doi.org/10.15454/RMIEJM, and flexible barrier elongation measurement: https://doi.org/10.15454/9HUDGG.

Additional information

Funding

This work was funded by the French Ministry of Environment (Direction Générale de la Prévention des Risques—Ministère de la Transition Ecologique et Solidaire) within the multirisk Agreement SRNH-IRSTEA 2019 (Action FILTOR).