Publication Date:
2014-10-17
Description:
ABSTRACT The role played by the texture of the sediment supply on channel bed adjustments in gravel-bed rivers is poorly understood. To address this issue, an experimental campaign has been designed. Flume experiments lasting 96 hours in a 9-m long, 0.60 m-wide have been performed with different sand-gravel mixtures as feed textures. The response of the surface texture has been found to be highly dependent on the grain size distribution of the feed. When the feed texture included gravel, the finest fractions of the sediment supply infiltrate beneath the surface. Conversely, sand remains on the surface when the feed texture lacks gravel. This different textural response becomes obscured when water discharge increases. Further, the sediment transport rate approaches the feed rate differently depending on the content of gravel in the feed texture. When a small proportion of gravel is part of the feed texture, bedload transport rate asymptotically approaches the feed rate. However, when a significant fraction of gravel is part of the feed grain size distribution, bedload transport rate approaches the feed rate by following an oscillatory path. These findings have been verified in terms of a one-dimensional numerical model. This modelling reveals that the higher the differences in mobility among the grain sizes contained in the feed texture, the more evident is the non-asymptotic transient trend towards equilibrium.
Print ISSN:
0043-1397
Electronic ISSN:
1944-7973
Topics:
Architecture, Civil Engineering, Surveying
,
Geography
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