Effect of bed morphology on flow mixing length at river confluences

MIXING processes at river confluences have an important bearing on problems such as pollutant dispersal and the management of river systems, but remain poorly understood. Previous studies 1–11 have indicated that flow mixing downstream of a confluence is a slow process, typically completed at distan...

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Bibliographic Details
Published in:Nature (London) 1995-01, Vol.373 (6510), p.138-139
Main Authors: Gaudet, Jocelyn M, Roy, André G
Format: Article
Language:English
Subjects:
Earth sciences
Earth, ocean, space
Exact sciences and technology
Freshwater
Humanities and Social Sciences
Hydrology
Hydrology. Hydrogeology
letter
multidisciplinary
Rivers
Science
Science (multidisciplinary)
Weights & measures
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Summary:MIXING processes at river confluences have an important bearing on problems such as pollutant dispersal and the management of river systems, but remain poorly understood. Previous studies 1–11 have indicated that flow mixing downstream of a confluence is a slow process, typically completed at distances greater than 100 times the channel width. Bed morphology is now emerging as a critical factor: flume experiments have shown that the width to depth ratios 12 and height discordance 13,14 between the confluent channels should influence mixing rates 12–14 . But the magnitude of these effects in real rivers is not known. Here we report measure-ments from three river confluences of moderate size which show that bed discordance can markedly increase mixing rates. For the rivers studied, mixing is complete at distances five to ten times shorter than those reported previously.
ISSN:0028-0836
1476-4687
DOI:10.1038/373138a0