Research press release


Nature Geoscience

Meandering rivers be dammed


Jose Constantineたちは、1985年から2013年のランドサット人工衛星画像を解析して、アマゾン川の屈曲が水平方向に移動する様子を追跡した。川が進化するにつれて、その蛇行は外側に移動し川はより曲がりくねった形状になる。研究者たちは、川の蛇行が移動する速さは川に供給される砂とシルトに依存していることを発見した。より多くの堆積物を運ぶ川の蛇行は、少ない堆積物を運ぶ場合よりも速く移動し、川が途切れてU字形の湖として残る頻度がより高くなる。


Greater amounts of sediment carried by lowland rivers drive the reshaping of floodplains in the Amazon Basin, according to a study published online in Nature Geoscience. These findings are relevant as the Amazonian river system may be significantly altered by proposed mega-dams that would disrupt sediment supplies.

Jose Constantine and colleagues analysed Landsat satellite imagery from 1985 to 2013 to track the lateral migration of river bends in the Amazon. As rivers evolve, their meanders migrate outwards and the rivers become more sinuous. The researchers 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.

doi: 10.1038/ngeo2282


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