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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Sediment management and morphodynamics : Hydro-morphodynamic differences induced by different angles in an
Hydro-morphodynamic differences induced by different angles in an
Confluences, within the fluvial network, are considered particular areas with great ecological value, where flow dynamics
and bed morphology are complex and highly three-dimensional. Several parameters influence the morphodynamics and
hydrodynamics of river confluences including discharge and momentum ratios, angle of confluence and sediment
transport. Confluences with low discharge and momentum ratios, where narrow steep tributaries with high sediment load
join a wide low-gradient main-channel that provides the dominant discharge, are often observed in the Upper-Rhone river
in Switzerland. Few existing studies have looked at the hydro-morphodynamics of this type of river confluences
considering sediment discharge in both confluent channels. This paper aims to analyze the influence of the confluence
angle on the flow dynamics and bed morphology of this type of confluences in an experimental facility under movable bed
conditions. For that purpose, two experiments were carried out in a laboratory confluence with low discharge and
momentum ratios (Qr = 0.11 and Mr = 0.16 respectively), and with two different confluence angles (α = 90° and 70°).
During the experiments, two distinct poorly shorted sediment mixtures were supplied into the tributary and into the main
channel at constant but different rates for each flume. The experiments were run until equilibrium in bed morphology was
reached. During the experiments bed topography surveys were systematically recorded, and water surface was measured
at equilibrium. These measures illustrate the bed topography evolution during the experiments, and the confluence
hydrodynamics at equilibrium. The results show that different confluence angles resulted in different flow regimes and bed
elevations in the tributary. Also, the distinct angle configurations yielded different water surface elevations in the main
channel upstream of the confluence.
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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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