The draft London Sustainable Drainage Action Plan, which is open for consultation for three months from today, aims to avert the risk of major flooding which London is likely to face by 2050 thanks to sewers which are approaching the limits of capacity.
Seventeen per cent of permeable ground surface in London has been lost over the last 40 years, largely thanks to the trend for home-owners to pave over their front gardens. This has effectively "waterproofed" the city, driving more rainwater into London's 150-year-old drainage system. Without action, even normal rainfall is predicted to cause flooding in the capital.
The new plan, launched in partnership with Thames Water, the Environment Agency and London Councils, identifies potential flooding hotspots across the city and proposes ways of diverting rain back from the sewers into the soil with rain gardens or green roofs.
It intends to cut surface water flows in the sewer network by 1 per cent each year, aiming for a 25 per cent reduction by 2040.
Thames Water has also announced today it will put £20m into funding green infrastructure projects over the next five years, with an aim of creating 20ha of rain gardens and other similar SUDS measures to capture rainwater.
In addition to SUDS measures, the Thames Tideway Tunnel – a major new sewer that will protect the River Thames from sewerage overflows - is being built by Bazalgette Tunnel Limited. The company will sponsor the creation of a full-time post at the Greater London Authority to work in concert to implement the London Sustainable Drainage Action Plan.
The draft plan was launched by the Deputy Mayor for Environment and Energy Matthew Pencharz at Derbyshire pocket park, a new rain garden in Tower Hamlets that was part-funded by the Mayor.
A flooding 'heat map' published today also shows the areas of London where the sewer network will be at full capacity by 2050, with associated flooding risk.