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| Titel |
A generic Froude scale model study of massive bedload deposition in a debris basin |
| VerfasserIn |
Guillaume Piton, Alain Recking |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250152689
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| Publikation (Nr.) |
 EGU/EGU2017-17557.pdf |
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| Zusammenfassung |
| Sediment trapping structures, such as gravel deposition basins, are regularly implemented in
mountainous context for flood hazard mitigation. These structures should ultimately trap
gravels when their excess may aggravate the downstream flood hazard, while, the
remaining time, allowing a suitable background sediment continuity. Such optimized
designs require a sufficient knowledge of the flow features and geomorphic processes
implied in gravel trapping. A generic Froude scale model of a 10%-steep, bedload
deposition basin, with a slit dam and without outlet structure, is presented in this
work.
Accurate photogrammetry and large scale particle image velocimetry (LS-PIV) were
combined to study the geomorphic patterns and to reconstruct the flows. The emergence of
self induced cycles of braided and channelized flows, with intense grain size sorting, is
described. It sheds light on the similarity of bedload trapping with alluvial fan formation or
fluvial delta development.
The deposition slope, a key parameter in the structure design, is more precisely
studied. The measurements are correctly estimated by a new simple equation, which is
developed from prior works dedicated to steep slope stream hydraulics and bedload
transport.
The analysis demonstrates additionally that, despite the steepness of the studied
conditions, most flows are subcritical due to roughness adjustment. We finally highlight that
morphologically-active flows, i.e., with dimensionless shear stress higher than the
threshold for motion, have Froude number ≈ 1; i.e., that a critical flow hypothesis
seems reasonable, as a first approximation, to describe flows over massive bedload
depositions.
This new dataset, with complete geomorphic and flow measurements, in diverse
conditions, may be used as reference to try and test numerical approaches of the
phenomena. |
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