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Flood Retention Dam

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Large dam which stores floodwater for a short period during storm events. Water is released at a controlled rate through a low-level outlet pipe. Cost $2 - $3 per cubic metre of bank.


These structures are used to control downstream flooding, to protect eroding gully heads and to facilitate the collection and disposal of water.


High risk of failure in tunnel prone soils.

Must have adequate flood bypass facilities.

Requires flat wide valley to achieve high storage efficiency.


There are not many sites well suited to these structures due to poor water storage conditions.

Design is difficult due to the lack of detailed stream flow data.