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| Titel |
The role of bed surface configuration on river response under increasing flows |
| VerfasserIn |
Carles Ferrer-Boix, María A. Elgueta, Marwan A. Hassan |
| 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 |
250148357
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| Publikation (Nr.) |
 EGU/EGU2017-12607.pdf |
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| Zusammenfassung |
| This research aims to explore how bed surface configuration influence channel evolution,
vertical and downstream sediment sorting, and sediment transport in gravel bed streams under
varying flows. While a significant body of research has been focused on channel evolution
under constant flow regimes, few studies have focused on the impacts of flow variations in
channel adjustments. Particularly, we are interested in examining the impact of the degree
of bed surface coarsening and particle arrangement on channel adjustments and
sediment transport rates. To this end, we conducted a set of experiments in a 0.55
m-wide, 5 m-long tilting flume. Flow discharge during the runs was initially held
constant at 25 l/s for a period of time after which discharge was gradually increased
at steps of certain duration. Flow rates during the rising limb of the hydrographs
ranged from 26 l/s to 40 l/s. Initial bed slope was 0.04 m/m for all runs. Some of the
experiments were conducted under no feed conditions while others were carried out with
sediment supply, which ranged from 1 kg/h to 10 kg/h. The feed texture in these
latter runs was identical to that of the original mixture (Dg = 5.65 mm and σg =
3.05). Bed slopes and surface configuration were obtained after varying times of
conditioning under constant flow and no feed. Data acquisition included: 1) bed surface
images covering the entire flume, 2) bed scans at 2 mm resolution of the whole flume
and 3) real-time measurements of bedload transport (rate and texture) at the outlet
of the flume. This set up allows us to obtain fractional particle mobility, i.e. how
much bed area covered by a particular grain size changed at a given time and to
link to sediment transport rates. Data gathered from this study 1) will contribute to
better understanding of river dynamics under unsteady flow conditions (floods)
and 2) will help us improve sediment transport predictions under such conditions. |
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