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| Titel |
Artificially generating sediment incipient motion in natural conditions |
| VerfasserIn |
Frederic Gob, Geoffrey Houbrechts, Alba Linares Carreté, Eric Hallot, Yves Nedelec, Yannick Levecq, François Petit |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250040345
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| Zusammenfassung |
| Incipient motion thresholds for gravel bed rivers are studied in flumes and natural rivers. Flume studies allow variables such as channel slope, water velocity, water depth, sediment size and sediment composition to be controlled. Meanwhile, in the field, the incipient motion of particles is studied in natural conditions allowing the structure of the bed and the flood characteristics to be considered. Though much less developed, an intermediate possibility also exists. By artificially accelerating near bottom velocity of the water flow in a small portion of the bed, it is possible to initiate sediment transport. This allows sediment incipient motion to be observed in natural conditions while controlling the water velocities.
The Cemagref (HHLY) has developed a device which confines water flow in a small tunnel on the bottom of the riverbed. It was developed in order to create a boundary layer similar to the one generated by natural flow. Water is injected into a filter which smoothes the flow before it enters a Plexiglas tunnel where sediment motion is observed. The flow is accelerated by two large pumps that allow flow velocities of up to 2.5 m/s in a small area 40 cm long, 20 cm wide and 12 cm high. As the water flow is confined, large scale turbulence similar to that occurring in natural rivers cannot be reproduced using the device. The velocity profile in the tunnel is stable and in equilibrium with the riverbed.
Sediment motion was observed using this device on three Belgian gravel bed rivers (3.5 cm
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