A new study of the Amazon River basin shows lowland rivers that carry large volumes of sediment meander more across floodplains and create more oxbow lakes than rivers that carry less sediment.
The findings have implication for the Amazonian river system, which may be significantly altered by proposed mega-dams that would disrupt sediment supplies.
Researchers from Cardiff University's School of Earth and Ocean Sciences examined 20 reaches within the Amazon Basin from Landsat imagery spanning nearly 20 years (1985 to 2013).
They found rivers transporting larger amounts of sediment migrated more, and noted that channel movement did not depend on either the slope of the channel or the river discharge.
The research gives scientists insight into the contrasting behavioural properties of rivers where sediment is an imposed variable – e.g. resulting from glacial, volcanic, or human activity – and rivers were the main sediment supply is from local bank erosion.
Dr José Constantine, Lecturer in Earth Sciences at Cardiff University's School of Earth & Ocean Sciences and lead author of the paper said: "We found that the speed at which the meanders migrated for each of the rivers studied depended on the river's supply of sand and silt. The meanders of rivers carrying more sediment migrated faster than those carrying less sediment, and were also more frequently cut off and abandoned to form U-shaped lakes. If sediment loads are reduced — by a dam, for example — meander migration is expected to slow, and thus the reshaping of the floodplain environment is affected."
Notes to Editors
The paper, 'Sediment supply as a driver of river meandering and floodplain evolution in the Amazon Basin', will be published on Nature Geoscience's website on Sunday 02 November at 1800 London time at: http://dx.doi.org/10.1038/ngeo2282
The full letter to Nature Geoscience is attached, together with an image showing the sinuosity of reaches studied in the Amazon Basin.
Academic contacts
Dr Jose Constantine, Lecturer in Earth Sciences, School of Earth & Ocean Sciences, Cardiff University: Tel: +44 (0)29 208 70642 mobile +44 (0)7508 046740; ConstantineJA@cardiff.ac.uk
Dr Eli Lazarus, Lecturer in Earth Sciences, School of Earth & Ocean Sciences, Cardiff University: Tel: +44 (0)29 208 75563 ; mobile: +44 (0)7580 330 792; LazarusED@cf.ac.uk @envidynxlab
Media contact
Heath Jeffries, Communications Manager, Cardiff University: +44 (0)2920 870917; mobile +44 (0) 7908 824029; jeffrieshv1@cardiff.ac.uk
Journal
Nature Geoscience