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Article via waterbriefing.

A major £14m sustainable drainage scheme set to be constructed in Nine Elms and developed through a partnership between Thames Water and the Nine Elms Vauxhall Partnership will be a further contribution to reducing flood risk in London.

Thames Water and other members of the innovative Partnership, including Wandsworth Council, Lambeth Council, the GLA and local developers, will work together on the project, which will result in rainfall landing on an area equivalent to 20 football pitches draining into the Thames instead of entering the local combined sewer. This reduces flood risk and saves the energy and cost of pumping and treating rainwater after it mixes with waste from sinks and toilets.

The risk of flooding in London is steadily increasing as the population heads towards 10 million, green areas are paved over and flash downpours strike more frequently. The capital has outgrown its combined sewers, which were built for a smaller, more permeable city 150 years ago by Sir Joseph Bazalgette.

In response and in tandem with the Lee Tunnel and under-construction Thames Tideway Tunnel super sewers, Mayor Boris Johnson has set an ambitious target for London to better manage its rainwater more sustainably. The aim is to achieve a 25% reduction in surface water flows in the Victorian sewer network by 2040, to reduce the growing flood risk and improve water security.

Nine Elms on the South Bank AerialCommenting on the scheme, Thames Water sustainability director Richard Aylard said:

“It is about putting surface water back where it belongs – in the river. By keeping the rain out of our combined sewers we are removing unnecessary pressure on our network, as London’s population continues to grow and the climate changes.”

“Development and regeneration across London is a major opportunity to do something different with surface water – to take it out of sewers and create additional capacity for new homes and businesses, and allow areas like Nine Elms on the South Bank to thrive. Initiatives like this will also help to prolong the life of the Thames Tideway Tunnel.”

Leader of Wandsworth Council and co-chair of the Nine Elms Vauxhall Partnership, Ravi Govindia, deacribed the project as the city’s most ambitious sustainable drainage network and a real step forward for London’s sustainable infrastructure.

Nine Elms on the South Bank is undergoing a major regeneration programme and is now coming to life as a vibrant new central London quarter. The area’s key attractions will include a revived Battersea Power Station, the new US and Dutch embassies, Vauxhall Pleasure Gardens, Nine Elms Park and a stretch of Thames Riverside Walk lined with cafes, bars, shops and galleries.

Two new tube stations are being built, alongside schools, around 4,000 affordable homes, health centres, a high speed data network, a second riverbus pier and a cycling and pedestrian network.

The already overstretched sewerage network would not be able to cope with the additional demands arising from the development, so Thames Water, working with the Nine Elms Vauxhall Partnership, developed the integrated water management strategy, which seeks to remove as much rainwater as possible, through the creation of a new surface water network.

The £14 million scheme is unique, not only in its scale, but also because of the interaction with developers, whose own schemes include a variety of features to capture, slow and reuse rainwater through measures such as green roofs, swales and streets incorporating rainwater gardens.

These design features will allow water to evaporate back into the atmosphere, irrigate plants and generally slow and reduce the volume of rainwater before it enters the new surface water network.

The project will capture and redirect surface water run-off from nine development sites across the Nine Elms on the South Bank, with scope to extend it in future. Surplus surface water that is collected after heavy rainfall will be lifted into the Thames via an upgrade to a pumping station on Ponton Road.

Last year Thames Water launched a £20m campaign to find new ways to drain 20 hectares of hard impermeable surfaces – an area equivalent to 30 football pitches. Over the next five years, the company’s Twenty 4 Twenty initiative will introduce sustainable drainage systems to slow the rainwater down and ideally completely remove it from entering the sewers again.