What is a Detention Basin?
Surface water flooding can happen very quickly, causing major damage to homes, roads and land. Detention Basins temporarily hold excess stormwater and gradually release it over time reducing flooding and erosion downstream. When dry, the area usually used for recreational purposes. Detention Basins are a form of Natural Flood Management (NFM) which enhances the local green/blue infrastructure network while also providing associated social, ecological and environmental benefits.
Where have we built Detention Basins?
Maldon Flood Alleviation Scheme
Essex County Council, in partnership with Maldon District Council delivered a combination flood alleviation scheme that intercepts, transports and stores surface water run-off at times of heavy rainfall, slowly releasing it back into the local downstream sewer at a controlled rate. The scheme turned the open space adjacent to the Community Centre into a multi-purpose flood storage area holding up to 5,600m3 of water.
The scheme protects up to 21 residential properties in the Brickhouse Farm area, and reduces flood risk to over 170 others in the Maldon. The basin functions as a temporary wetland, bringing aesthetic and ecological improvements to the area.
Guildford Flood Alleviation Scheme
This year, Essex County Council in partnership with Harlow District Council, started working on a flood alleviation scheme within the public open space near Guilfords, Old Harlow. This scheme is designed to alleviate surface water flooding as well as to enhance amenity and biodiveirsty for the area.
The scheme consists of a landscaped basin with a preferential overspill from Harlowbury Brook, so that in times of extreme rainfall, the water flows into the basin and is stored temporarily and released back into the Brook at a later time. This provides flood alleviation benefits to the neighbouring properties at high risk of surface water flooding. The earth banks have been planted with wildflowers to add colour and encourage local wildlife. Supplementary tree planting include a multitude of species, including Walnut, which has historically been present on the site. The Guildford Flood Alleviation Scheme will protect 47 properties from flooding, as well as reducing flood risk to over 100 properties in the wider area.
Braintree Flood Alleviation Scheme
Essex County Council, in partnership with Braintree District Council delivered a flood alleviation scheme within the Bradford Street area of Braintree to reduce surface water flood risk to nearby properties. The scheme consists of a a long earth bund, surrounding a landscaped attenuation area, to capture, store and regulate the downstream flow of surface water. By making the outlet pipe very small, the discharge back into the bordering watercourse is slowed down. Upstream, the scheme also includes a spillway and weir that during high flow diverts excess water into the storage area, but allows water to pass below during normal conditions.
By moving soil around the site rather than building concrete walls, the scheme reduces it's environmental impact, it always allows the field to be used as a playing field when dry. The scheme protects 46 properties from flooding.
Pitsea Flood Alleviation Scheme
Essex County Council (ECC) in partnership with Basildon Borough Council delivered a flood alleviation scheme to reduce the risk of flooding to 48 properties within the Pitsea area of Basildon.
The scheme consists of two earth bunds and attenuation areas to capture, store and regulate the downstream flow of surface water into the existing drainage network. The basins remain dry and normal conditions, and using natural elements, the scheme retains the visual amenity, openness and usability of Kent View Recreation Ground as a public open space.