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| Titel |
Physical modelling of sediment transport in mountain torrents upstream of open check dams |
| VerfasserIn |
Sebastian Schwindt, Mário J. Franca, Anton J. Schleiss |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106492
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| Publikation (Nr.) |
 EGU/EGU2015-6166.pdf |
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| Zusammenfassung |
| Dynamic morphological processes in mountain torrents do not only attract the attention of
many contemporary researchers, but are also a relevant issue for the design of flood
protection measures in the downstream sections where dwellers may be threatened by the
important potential of flows with high concentration of sediments. Events which have a
morphodynamic effect are simulated at the Laboratory of Hydraulic Constructions (LCH) in
order to optimize the design of a flood protection measure, notably open check dams.
Different scenarios with a fix bed consisting of boulders as well as mobile beds are studied
and the influence of flow constrictions, i.e. distinct geometric configurations of open check
dams are analysed. Three varying water pumped discharges in the order of 5 to 20 l/s are
tested with progressively increasing solid discharges of 1, 3 and 6 % of the liquid discharge
according to the transport capacity. The moistened sediments are introduced via a system of
conveyor belts and are then mixed with the liquid discharge in an about 3 m long rough
trapezoidal channel with a base width of 24 cm. The mean diameter Dm of the
injected sediments is 0.86 cm and the dimensionless grain size distribution is in
line with a normalized shape derived from over 60 streams in the Alps. A wide
range of frequent floods in morphologically diverging types of mountain torrents is
covered, in particular regarding the sediment availability in the catchment area and
along the river. A basic assumption here is considering that the frequent floods
are floods with return periods between 1 to 5 years and are the most important
process in terms of amounts of sediment transport. This may be arguable for some
mountain torrents and landscape effective processes which are driven by floods with
return periods of more than several decades. In order to identify benchmarks for
hydraulic parameters which lead to the obstruction of flow restrictions at mountain
torrents, the water depth is evaluated using ultrasonic probes, the flow velocity
is derived by particle image velocimetry (PIV) and the occurrence of sediment
depositions as well as the sediment outflow are observed. The results are in particular
analysed in the moment when the flow constriction causes rising back water effects. |
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