Valera-Prieto et al. (2025) Breaking the jam: Bridge wood-jam break during a flash flood in a Mediterranean river, insights from hydrodynamic modeling and post flood observations

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2025
• Date: 2025-12-16
• Authors: Llanos Valera-Prieto, Marcos Sanz-Ramos, Ernest Bladé, Virginia Ruiz-Villanueva
• DOI: 10.1016/j.ejrh.2025.103032

Research Groups

• RISKNAT Research Group, Department of Dynamics of Earth and Ocean, Geomodels Institute, University of Barcelona, Spain.
• Flumen Research Institute, Polytechnic University of Catalonia (UPC Barcelona-Tech), Spain.
• International Center of Numerical Methods in Engineering (CIMNE), Spain.
• Institute of Geography, University of Bern, Switzerland.

Short Summary

This study reconstructs an extreme flash flood in the Francolí River to analyze how large wood (LW) transport and bridge clogging influence hydraulic behavior. The research demonstrates that wood-jam formation and sudden breakage cycles create transient surges and significantly increase upstream water levels, factors often overlooked in standard flood modeling.

Objective

• To investigate the dynamics of large wood recruitment, transport, and bridge accumulation during flash floods and to quantify the hydraulic impacts of wood-jam "blockage–breakage" cycles on flood hazards.

Study Configuration

• Spatial Scale: A 1.6 km reach of the upper Francolí River near L’Espluga de Francolí, Spain (catchment area: 856 km²).
• Temporal Scale: Reconstruction of the 24-hour extreme flash flood event of October 22–23, 2019.

Methodology and Data

• Models used: Iber-Wood, a coupled 2D hydrodynamic and wood transport model. It utilizes a Lagrangian approach for wood (represented as cylinders) and solves 2D Saint Venant equations for hydrodynamics and Meyer-Peter & Müller equations for bedload sediment transport.
• Data sources: 1 m resolution Digital Elevation Model (DEM), post-flood field surveys, drone-based imagery, high-resolution orthophotos, and hydrometeorological data from the Catalan Water Agency (ACA) and the Montblanc gauging station.
• Experimental Design: 31 simulation scenarios testing different peak discharges (ranging from 501 m³/s to 1330 m³/s), varying bridge opening percentages (15%, 50%, 100%), and comparing "water-only" vs. "water-sediment-wood" configurations.

Main Results

• Model Performance: Scenarios incorporating sediment and wood (HSM) provided a superior match to observed flood marks (NSE > 0.8) compared to water-only models, which underestimated water depths by up to 1.5 m.
• Wood Retention: Retention efficiency at bridges decreased as discharge increased; at lower flows (501 m³/s), ~55% of logs were retained, whereas at high flows (960 m³/s), only ~10–12% remained in the reach.
• Blockage–Breakage Cycles: The model successfully replicated the formation of wood jams that temporarily impounded flow, followed by sudden breaches. These breaches generated surges (up to 1 m rise in water level) and localized high-velocity zones (>2 m/s).
• Morphodynamics: Significant erosion (>1 m) was identified near bridge piers and anthropogenic walls, while deposition was concentrated downstream of bridges following jam releases.
• Computational Efficiency: GPU-parallelized versions of the model reduced hydrodynamic simulation times by approximately 150 times compared to traditional CPU processing.

Contributions

• Process Reconstruction: Provides the first explicit numerical simulation of bridge wood-jam formation and sudden breaching during a real-world flash flood.
• Hazard Assessment: Quantifies the "surge effect" of wood-jam releases, proving that organic debris can cause discharges to exceed peak hydrograph estimates.
• Methodological Advancement: Validates the use of 2D coupled models (Iber-Wood) for predicting complex geomorphic responses in Mediterranean mountainous rivers, supporting the design of more resilient infrastructure.

Funding

• Spanish Ministry of Science, Innovation and Universities: Project "Monitoring, modelling and integration of methods for the control of active mountain processes" (MINEICO-AEI/FEDER, UE: CGL2017–84720-R).
• Institutional Support: University of Barcelona, Polytechnic University of Madrid (UPM), and University of Lausanne (UNIL).

Citation

@article{ValeraPrieto2025Breaking,
  author = {Valera-Prieto, Llanos and Sanz-Ramos, Marcos and Bladé, Ernest and Ruiz-Villanueva, Virginia},
  title = {Breaking the jam: Bridge wood-jam break during a flash flood in a Mediterranean river, insights from hydrodynamic modeling and post flood observations},
  journal = {Journal of Hydrology Regional Studies},
  year = {2025},
  doi = {10.1016/j.ejrh.2025.103032},
  url = {https://doi.org/10.1016/j.ejrh.2025.103032}
}

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