Rivers are much wider than the channels we associate them with. The areas next to rivers, which are only covered by water during floods, are also part of the river system. Known as floodplains, in their natural condition they are an important ecological part of this system: they filter and store water, secure both natural flood protection and the healthy functioning of river ecosystems, and help sustain the high biological diversity present there.
A noter : "Floodplains are an important part of Europe’s natural capital, covering 3-5 % of the continent’s area and 50-60 % of its terrestrial Natura 2000 sites." Briefing no. 14/2018 de l'Agence européenne de l'environnement pour l'instant disponible en anglais