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Image-based Lagrangian Particle Tracking in Bed-load Experiments
Published on: July 20, 2017
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Multi time scale influence of dams on bedload transport
Louis Gilet1, Frédéric Gob1, Emmanuèle Gautier1
1Université Panthéon-Sorbonne (Paris 1), Laboratoire de Géographie Physique, CNRS UMR8591, 2 Rue Henri Dunant, 94320 Thiais, France.
Journal of Environmental Management
|September 22, 2023
Summary
Dams significantly alter riverbed transport by reducing floods and changing downstream morphology. Inherited riverbed features, shaped over decades, now primarily control sediment movement, impacting restoration efforts.
Area of Science:
- River ecology and geomorphology
- Anthropogenic impacts on fluvial systems
- Sediment transport dynamics
Background:
- Dams are major anthropogenic disturbances affecting river ecosystems and geomorphology.
- Understanding dam impacts on downstream bedload transport is crucial for river management.
Purpose of the Study:
- To investigate the mechanisms of dam influence on downstream bedload transport in French gravel-bed rivers.
- To analyze hydrological and morpho-sedimentary changes at short and long timescales.
Main Methods:
- Utilized radio frequency identification (RFID) tracers to monitor bedload displacement over short timescales.
- Conducted morpho-sedimentary characterization of riverbeds, including long and cross-profile analyses.
- Examined long-term (21-28 years) hydrological data on flood regime alterations.
Main Results:
- Dams reduced mean annual maximum floods (9–40%) and flood event frequency (27–73.5%).
- Large dams (>15m) led to sediment deficit, bed coarsening, and vegetation encroachment, significantly reducing bedload transport (6.8–45m).
- Medium dams (<10m) had less impact, resulting in higher bedload transport distances (78–315m).
Conclusions:
- Dam-induced alterations in flow and sediment discharge modify downstream morphology.
- Inherited riverbed morphology is now the primary factor controlling downstream bedload transport.
- River restoration strategies must consider these long-term morphological legacies.
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