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  4. Hydro-morphodynamic differences induced by different angles in an experimental discordant confluence
 
conference paper

Hydro-morphodynamic differences induced by different angles in an experimental discordant confluence

Guillén Ludeña, Sebastián  
2015
Proc. of Int. Congress IAHR 2015
IAHR 2015

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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Type
conference paper
Author(s)
Guillén Ludeña, Sebastián  
Date Issued

2015

Published in
Proc. of Int. Congress IAHR 2015
Volume

on-line version

Subjects

river confluences

•

confluence angle

•

discordant bed

•

sediment transport

•

supercritical flow

Note

[1039]

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
PL-LCH  
Event nameEvent placeEvent date
IAHR 2015

The Hague, The Netherlands

June 19- July 3, 2015

Available on Infoscience
October 15, 2015
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/119871
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