New rain gardens with the largest sustainable drainage system in central London to improve transport network and climate resilience

New Marylebone Flyover rain gardens are ready for rainfall after children in the Eco Club at nearby Christ Church Bentinck School put the final plants in the ground. The rain gardens are the largest sustainable drainage systems (SuDS) in central London. This project will add new plants to make the local area more pleasant, boost biodiversity, improve surface drainage and make the network more resilient to climate change and flooding.

Located at the busy A5 junction with the Marylebone Flyover, more than 3,500 square metres of rainwater collection area has been installed at the site of a disused subway system, known locally as the Joe Strummer Subway, where the late punk frontman was known to busk and entertain passers-by before he hit fame with The Clash. The ramps and stairs of the disused underpass system, which led to the subway, have been transformed into porous rain gardens, designed to capture approximately 3,500 square metres of storm water run-off and hold around 30,000 gallons of rainwater in total. The gardens are designed to help mitigate London’s increasing risk of extreme weather, including larger storms seen only once in 30 years. They reduce the risk of localised flooding and the number of occasions in which sewer overflows occur.

On the surface, the planted gardens can be seen on three corners of the road within the Marylebone Flyover underpass and are around 300 square metres when combined, which would fit 10 New Routemaster buses. The gardens have been planted with 11 trees, 95 shrubs, more than 1,100 perennial plants and almost 2,300 bulbs in total. Londoners can spot flowering species like pink geraniums, orange-coloured Kniphofia and blue wood-aster in full bloom, adding colour, life and nature to these urban streets. The plant species have been curated to support pollinating insects when in season and can thrive in local climate and soil conditions as they require minimal maintenance, tolerating both extreme wet and dry conditions.

This Marylebone Flyover rain garden scheme was a joint collaboration between TfL, the Greater London Authority (GLA) and Thames Water, with the Marble Arch London BID committed to fund and run the maintenance work on the gardens. The scheme was part funded by Thames Water and the GLA under the Green Infrastructure Fund programme where £1m was allocated for greening projects on the TfL Road Network. TfL’s recent Business Plan sets out how between now and 2027/28, TfL will invest £6m specifically to improve its understanding of the impacts of climate change, as well as help supplement existing projects to add additional green infrastructure and SuDS.

TfL has worked with Westminster City Council to deliver improved pedestrian crossings in the area as part of the Safer Junctions programme. Since public access to the subway system under the Marylebone Flyover was closed, pedestrians can continue to use the safe surface level signal-controlled crossings at the junction. As part of this, TfL extended the pavement outside Edgware Road Underground Station and removed a left turn slip lane to improve conditions for the thousands of people who walk across the junction throughout the day.

Penny Rees, TfL's Head of Healthy Streets Investment, said: "We are committed to making our network more resilient to climate change in the face of extreme weather conditions. These rain gardens at Marylebone Flyover will not only brighten up the local area that holds a special meaning to the community and fans of Joe Strummer, but also improves the surface drainage system to protect a busy junction from flooding. This welcome addition will increase biodiversity, as well as contribute to the Mayor's aim to improve our river water quality."

Mete Coban, Deputy Mayor for Environment and Energy, said: "This is a great initiative to help reduce flooding in the area, increase biodiversity and provide beautiful new gardens for residents and visitors to enjoy.

"Addressing the important issue of surface water flooding is one of many ways we are working with partners like TfL to make London more climate resilient, creating a fairer, greener city for all.”

Kay Buxton, Chief Executive of Marble Arch London BID, said: "We have been involved in this project since 2018 when the subway network was closed, so to see these rain gardens come to life marks such a significant milestone for Marble Arch BID. Our colleagues at TfL have a very strong commitment to delivering more green infrastructure on the capital’s main roads, to manage the impact of climate change and improve air quality. The delivery of these SuDS around the Marylebone flyover is a clear indication of the commitment of all the partners and funders involved. We were delighted to watch local primary school children - the next generation - plant the final flowers, putting nature so firmly front and centre right here in the heart of London."

Craig Boorman, Principal Environment Engineer at Thames Water, said: "This unique regeneration project shows how sustainable drainage can help our capital city to adapt to the impacts of more intense rainfall, while also being beautiful and enhancing for local communities.

"Sustainable drainage systems like this play a vital role in capturing rainwater, slowing the flow entering sewers which can reduce the risk of flooding and untreated discharges from storm overflows. We regard all discharges as unacceptable, and by working in partnership with one of key stakeholders, TfL, this project is a small step that demonstrates how we are taking action to improve the health of rivers.

"A more ‘spongey’ London will be better able to deal with heavy rain now and in the future, and the solution is to turn our urban landscape from grey to green."

Mrs Tyrrell, Headteacher of Christ Church Bentinck School, said: "As an ‘outstanding’ provider, we at Christ Church Bentinck School on Cosway Street, are passionate about empowering our children to be proactive in shaping a more sustainable future. This is particularly important for children and families who live in our capital city. ‘Responsibility’ is one of our school’s four values, here at Christ Church Bentinck School. Through their involvement in the Marylebone Flyover Rain Gardens project, our School Council and Class Champions – some of whom are also members of our Eco-team – have been able to take part in this initiative to enhance our local environment. The Marylebone Flyover Rain Gardens will help to beautify our local community and give the community a sense of pride and of ownership, contributing to a greener and more sustainable world."

TfL is installing SuDS on its network to help address surface water flooding. SuDS, like rain gardens, have permeable paving and green roofs mimic natural processes, slowing and reducing the amount of rain water reaching the drainage networks. TfL’s highways-based SuDS will not only reduce flooding risks but also support biodiversity and improve water quality in London’s rivers, supporting the Mayor's ambition for swimmable rivers in the capital by 2034. Installing more sustainable drainage is a key part of TfL's plans to make the capital more resilient and biodiverse, and will be increasingly important in future years as the climate changes.

TfL has an annual target to install 5,000 square metres of additional SuDS to help mitigate the impacts of climate change and installed more than 17,800 square metres of SuDS collection area on its road network to date. The completed Marylebone Flyover rain gardens have enabled TfL to reach more than 70 per cent of its current annual target. TfL is on track to surpass this in the 2024/25 financial year as it is expected to deliver additional SuDS on London Road Roundabout in Twickenham, which will add almost 2,000 square metres of SuDS collection area when completed. Elsewhere on its estate, as part of a major redevelopment work, the Kingston Cromwell Road Bus station will also add 1,620 square metres of SuDS collection area when completed.