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| Titel |
Modeling of replenishment of sediments on a water-worked gravel bed channel |
| VerfasserIn |
Carmelo Juez, Elena Battisacco, Anton J. Schleiss, Mário J. Franca |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250131379
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| Publikation (Nr.) |
 EGU/EGU2016-11783.pdf |
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| Zusammenfassung |
| The presence of dams causes a sediment deficit downstream. Hence, the surface
structure of the riverbeds is altered by this interruption in the sediment continuity
and
The presence of dams causes a sediment deficit downstream. The surface structure of the
riverbed is altered by this interruption in the sediment continuity and becoming
water-worked. The main morphological effects verified in these cases are thus the generation
of armored layers, bank instability, riverbed incision, changes in the channel width and
coarsening of the bed particles. These results impact on the riverbed topographic
variability and structure of the bedforms. Surface complexity is thus reduced with
further ecological implications. The lack of fine material and surface complexity
leads to the loss of aquatic and riparian habitats, limiting the possibilities for fish
spawning.
Nowadays, the revitalization of disturbed river reaches forms an integral part
of river management. Sediment transport and associated channel morphology are
understood as key processes for recreating and maintaining aquatic ecosystems. For this
purpose several replenishment techniques have been considered in order to supply
sediments lacking in the downstream reaches. The replenishment techniques can
be seen as a pulse-like addition of sedimentary material that initially disturbs the
channel.
In this work, the response of the flow to the complementary material which is
added in the channel is studied by means of the 2D shallow water equations in
combination with the Exner equation. The numerical scheme is built by means of a
weakly-coupled treatment between the hydrodynamic and morphodynamic equations leading
to an efficient and robust solution. Computational outcomes are compared with
experimental data obtained from several replenishment configurations studied in the
laboratory.
The results are analyzed by means of: (i) temporal evolution of the material spreading, (ii)
occupational ratio along the channel which is the area percentage that is covered by the
replenishment material, (iii) travel distance of the center of the pulse mass and (iv) effect of
the bed fining in the bed shear stress. The results of these experiments assist in further
evaluating how water-worked gravel bed channels evolve with artificial replenishment of
sediments.
This work was funded by the ITN-Programme (Marie Curie Actions) of the European
Union’s Seventh Framework Programme FP7-PEOPLE-2013-ITN under REA grant
agreement n_607394-SEDITRANS. The sediment replenishment experiments were funded
by FOEN (Federal Office for the Environment, Switzerland). |
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