A arm-death is the relictuelle part of old a Méandre or a braid which was isolated from a river or a delta. According to its age, the season and the weather context, it can be still out of water or drained,

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Arm-deaths can be dry or out of water, all the year or periodically. They are sometimes brutally but briefly flooded at the time of the Crue S, or on the contrary behave like phreatic rivers (supplied with the tablecloth), when the substrate is permeable. On the long run, they tend to be filled, but after a certain time, and on several occasions, they can again be occupied by the river with the liking of its mistakes and the stage successionnel. The processes of erosion and sedimentation strongly differ there the EC what they are in the original river.

Characterization

One géomorphologiquement characterizes them for example by their length, depth, level of silting or atterissement, distance of the river or the river, their surface out of water and his variations, the frequency of connections with the river or the tablecloth, the width of the channel when there exists, his salinity, his age, his fauna or specific flora, degree of artificialisation (or Naturalité), etc

Ecological richness

When they were not filled, were polluted or transformed into ground of deposit receiving from the Boues of polluted clearing out, they are mediums generally rich in Biodiversité or with strong biological productivity which contributes to enrich the river ecosystem S. They can play the part of ford for the species of Wetlands, in a ecological Réseau local and total (for the migrating water birds in particular). They are often tanks of Espèces pionnières.

For at least 500 years, except in the tropical forests and the zones far away from the human activities, the dead meanders and arms have tended to disappear, with the profit of navigable and channeled axes whose ecological functions are very degraded. It is the case for example for the the Rhine and the the Rhone that one tries renaturer today to improve water quality of it.

See too

• Meander
• Ecology of the biological landscape
• Corridor
• Ripisylve
• Écotone
• Beaver
• Lône dead arm of the Rhone

External bonds

• Random links:

  Crystallite | Pierre Dubuc | -1296 | Bagnoregio | Jean-Henri Chambois