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| Titel |
The Grain-size Patchiness of Braided Gravel-Bed Streams – example of the Urumqi River (northeast Tian Shan, China) |
| VerfasserIn |
L. Guerit, L. Barrier, C. Narteau, F. Métivier, Y. Liu, E. Lajeunesse, E. Gayer, P. Meunier, L. Malverti, B. Ye |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7340
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| Digitales Dokument |
URL |
| Erschienen |
In: Sediment Transport and Landscape Dynamics (SALADYN) Workshop 2012 ; Nr. 37 (2014-02-11), S.27-39 |
| Datensatznummer |
250121287
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| Publikation (Nr.) |
 copernicus.org/adgeo-37-27-2014.pdf |
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| Zusammenfassung |
| In gravel-bed rivers, sediments are often sorted into patches of different
grain-sizes, but in braided streams, the link between this sorting and the
channel morpho-sedimentary elements is still unclear. In this study, the size
of the bed sediment in the shallow braided gravel-bed Urumqi River is
characterized by surface-count and volumetric sampling methods. Three
morpho-sedimentary elements are identified in the active threads of the
river: chutes at flow constrictions, which pass downstream to anabranches and
bars at flow expansions. The surface and surface-layer grain-size
distributions of these three elements show that they correspond to only two
kinds of grain-size patches: (1) coarse-grained chutes, coarser than the bulk
river bed, and (2) finer-grained anabranches and bars, consistent with the
bulk river bed. In cross-section, the chute patches are composed of one
coarse-grained top layer, which can be interpreted as a local armour layer
overlying finer deposits. In contrast, the grain size of the bar-anabranch
patches is finer and much more homogeneous in depth than the chute patches.
Those patches, which are features of lateral and vertical sorting associated
to the transport dynamics that build braided patterns, may be typical of
active threads in shallow gravel-bed rivers and should be considered in
future works on sorting processes and their geomorphologic and stratigraphic
results. |
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