In the context of Sustainable urban Drainage Systems (SuDS), attenuation is the process of temporarily storing excess surface water runoff during rainfall events and releasing it gradually at a controlled rate.
This helps reduce flood risk by preventing drainage systems and watercourses from becoming overloaded.
How Attenuation Works
- Collection: Rainwater runoff from roofs, roads, and other impermeable surfaces is directed into a storage system.
- Storage: Water is held temporarily in features such as underground tanks, attenuation ponds, swales, oversized pipes, or geocellular crate systems.
- Controlled Discharge: Flow control devices, such as vortex controls or orifice plates, regulate the release of stored water back into the sewer network or nearby watercourses at a safe rate.
Importance of Attenuation
- Flood Prevention: Attenuation reduces peak runoff flows, helping to protect downstream areas from flooding.
- Natural Drainage Management: It replicates the slower runoff rates that occur in undeveloped (greenfield) conditions.
- Regulatory Compliance: Attenuation is a key component of SuDS design and is often required to meet UK planning and flood management regulations.
Below-Ground Attenuation Storage
Below-ground attenuation systems are engineered SuDS solutions designed to temporarily store stormwater runoff beneath the surface during periods of heavy rainfall. Common forms include attenuation tanks, oversized pipe networks, and geocellular crate systems. These structures release water gradually into sewers or watercourses, reducing the risk of flooding and preventing excessive loading of drainage infrastructure.
Find out more about a range of SuDS Drainage & Attenuation solutions
Civils Store is a leading provider of SuDS drainage solutions including attenuation crates and chambers, distribution tanks and Polybed® drainage.
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