Retention area

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A retention area is a term used in water management and refers to an area that is mostly deeper than a river and that can be used as a flood area in the event of a flood runoff .

Their use weakens the flood wave, as the cross-section of the river is expanded considerably. Downstream, the flood wave rises more slowly, it is delayed and runs flatter. The retention is greater, the smaller the slope and the larger the floodplain. The water quantities stored on the retention area are released back into the river with a time delay after the flood peak.

The retention area is either artificially created by means of a hydraulic engineering measure or is a natural feature. The inflow to the retention area can often be controlled by human intervention and thus opened in a targeted manner.

In times when there is no flooding, the artificial retention area is mostly used for agriculture . If possible, this should take the form of pasture or forestry. Seldom used areas run the risk of increasingly high-quality use.

The creation of retention areas is a flood protection measure .

See also: floodplain