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You are here : eLibrary : IAHR World Congress Proceedings : 32nd Congress - Venice (2007) : THEME A: Engineering and Management of Fresh-water Systems : Bed load sheets and bed load fluctuations in gravel bed experiments
Bed load sheets and bed load fluctuations in gravel bed experiments
Author : Alain Recking, Cemagref
 The purpose of this research was to investigate the effects of grain sorting on bed load. Flume experiments were performed over graded sediment, for long durations, and a wide range of flow conditions. No equilibrium slope was obtained whatever the run and the experiment duration (up to more than 60 hours). Instead a periodic pattern fluctuation was observed, affecting the bed slope, the bed state (varying from armor to fined bed) and the bedload discharge. Two kinds of fluctuations were observed: short (length and time) fluctuations associated with the passage of bedload sheet (local bedslope changes) and large fluctuations associated with overall changes in bed morphology. Bedload sheet appeared to be the keystone for explaining the short fluctuation periods, but also the long-term periodic changes in bed morphology. We hypothesized, from steep slope observations, that bedload sheet would be produced by a local and efficient upstream grain sorting mechanism operating over a finite lenth Ls and producing sediment pulses which propagate downstream. A conceptual compartment model, based on this concept, was proposed to simulate slope fluctuations observed in long-term flume experiments. Even though presented in a rough form, it provides an illustration of a possible endogenous factor responsible for time scales affecting bedload.
File Size : 326,905 bytes
File Type : Adobe Acrobat Document
Chapter : IAHR World Congress Proceedings
Category : 32nd Congress - Venice (2007)
Article : THEME A: Engineering and Management of Fresh-water Systems
Date Published : 01/07/2007
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