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The Lost Effra project: Sustainable water management in London

Lost Effra, Sam MellishImage credit: Sam Mellish

Imagine if every household in London depaved their front garden, built a green roof on their shed or fitted a water butt to capture rainwater from their roof

The Lost Effra Project empowers communities to create green landscape features to increase local climate resilience and improve neighbourhoods for people and wildlife.

The project is based around the catchment of the culverted River Effra that runs through a highly urbanised and socially diverse area of south London, removing concrete and tarmac and creating new green spaces that manage rainwater more intelligently. The presence of the Effra, one of London’s "lost" rivers, in the sewers beneath the area, increases its vulnerability to flooding during heavy rainfall.

By working with local people on urban greening projects, we are making London more resilient to extreme weather while supporting the city's biodiversity and empowering people to create and maintain their own urban greenspaces.

The Lost Effra project began in 2013 after being commissioned by the Department for Environment, Food and Rural Affairs (Defra) and Carnegie Trust. It is now supported by Thames Water, Greater London Authority and Lambeth Council. There is also valuable input and assistance from community groups and private sector partners.

One of the project's first achievements was producing a report into delivering sustainable water management on a community scale, called A New Way to Manage Water. Since then we have been working with communities around Herne Hill and Brixton, creating new living landscape features such as green roofs, rain gardens and by removing hard paving to help to make the area more resilient to climate and environmental change.

See exactly what progress we've made by zooming in and clicking on this interactive map:





For more details and images of the individual projects completed as part of Lost Effra, see below.


Cressingham Rain Gardens, SW2

We worked with residents from the Cressingham Gardens estate, volunteer landscape architect David McCollum and Lambeth Council to create a 30 metre green corridor including a series of three rain gardens.

The rain gardens each receive rainwater from a downpipe from the roof of a large residential building next to the gardens. Rainwater that fell on this uninspiring area of grass was previously sent running downhill into the Brixton flood risk area is now caught and held temporarily in the gardens before being taken up by plants and naturally soaking into the ground.

Rainwater is now used to water the gardens, nurturing the plants and supporting the insects and birds that they provide the gardens act as important urban habitats for.

The project has been made a huge success by the residents to look after and maintain the gardens – many thanks to all of those who have been involved.

Courtesy of Sam Mellish


Depaving at Rosendale Allotments, SE24

One of the largest allotment sites in south London, Rosendale Allotments is an 18 acre steeply sloping clay site with a significant impact on flood risk in its surrounding area, Herne Hill.

The concrete forecourt that previously acted as a bottleneck for rainwater runoff from the site was transformed through a collaboration between Mace and London Wildlife Trust, working with plot holders and the Rosendale Allotment Association to remove the concrete forecourt. The previously impermeable surface has been replace it with 100 square metres of new wildflower meadow and recycled plastic block paving that can hold 80 cubic metres of rainwater runoff – enough to fill 8,000 baths!

Now when it rains, rainwater that flows down to the forecourt is stored in a thick layer of recycled crushed stone beneath the block paving and the sudden heavy flows of water that cause flash flooding in times of heavy rain are reduced. In time, the water evaporates back into the air, or is slowly released into the sewers after the main flow of runoff in a storm has passed.

The project acts as a valuable local example of depaving; showing ways of working with nature to reduce flood risk and boost local wildlife. It was funded by Mace, Lambeth Council and J. Coffey.

Rosendale Allotments depaving project
















London Wildlife Trust’s ongoing partnership with Mace through practical conservation on our reserves and outreach projects such as this one have helped us to win the Lord Mayor’s Dragon Award for partnership with the community. Click below to see the video.




Green roof workshops at Sydenham Hill Wood, SE26

Another key part of Lost Effra is to give local people the skills and knowledge to take on their own projects to create new living areas in their neighbourhoods through accessible and engaging workshops.

Through one day green roof workshops, we lead a group of volunteers through the process of building a small scale green roof through from design to planting. At the end of the day, we have built and planted a green roof and people go home with the skills and knowledge to build a green roof on their garden shed, flat roof or bike shelter.

Sydenham Hill Wood green roof workshop




Living with Rainwater

Living with Rainwater is a community guide to creating urban greenspaces for environmental resilience.

This is the Lost Effra project’s introductory guide to creating household scale rain gardens, building green roofs, depaving and fitting rainwater harvesting.

Click on the image, left, to access your free download. 

Climate Change Champions

Lost Effra has been running a series of exciting two-part school workshops with Key Stage 2 pupils at schools along the course of the underground River Effra.

Pupils take part in hands-on activities to learn about the history of our Victorian sewer system, where our water goes, and ways we can help out and improve our cities for people and wildlife by saving water and getting rid of concrete. They also get to interact with our scale SuDS model, and discover the benefits of rain gardens for wildlife. Each group finishes the mini-project with a group rain garden collage, to remind them to think green not grey! These workshops were funded by a Tesco Bags of Help grant, working with Groundwork.



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Main image: Cressingham Rain Gardens, SW2 Image Credit: Sam Mellish