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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Sediment management and morphodynamics : Laboratory analysis on silt infiltration into gravel bed
Laboratory analysis on silt infiltration into gravel bed
Author : ALBERT HERRERO(1), CELINE BERNI(2) & BENOIT CAMENEN(3)
ABSTRACT
Fine sediment infiltration into a gravel bed may have significant impact on environmental, socioeconomic and river
morphodynamics issues. Several human activities enhance fine sediment flux, either in the production zone due to
changes in land use or within the river system due to reservoir flushes or dredging. Understanding the mechanisms that
control this phenomenon can help to minimize impacts of such anthropic actions. A set of experiments has been
performed in the new tilting flume (18 meter long and 1 meter wide) of Irstea-Lyon hydraulics laboratory. Silt sized silica
(10-30 microns) and gravels (3-12 mm) are used as fine and coarse sediments, respectively. Fine sediments are
introduced for a specified concentration in a flow with fixed discharge, water depth and bed slope. All the explored
conditions correspond to fine sediment travelling in homogeneous suspension (wash load). Keeping the concentration
constant during each test, the process of infiltration of fine sediments into the gravel bed is analyzed and the influence of
flow velocity and fine sediment concentration is discussed. Fine sediment deposition takes place as a progressive filling
of the bed starting from the base of the channel and ending one to three diameters below the bed surface. The thickness
of the surface layer that remains unclogged in the equilibrium situation depends mainly on the bed shear stress. On the
other hand, a positive correlation is found between the suspended sediment concentration and the rate of infiltration with
time. Water mass exchange and turbulent structures that occur at the flow-bed interface seem to be the key
mechanisms that control fine sediment infiltration
File Size : 7,681,705 bytes
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Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Sediment management and morphodynamics
Date Published : 18/08/2015
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