Mayor launches London’s first action plan to avert major flooding risk

29 October 2015

London may be at risk from major flooding by 2050 without a radical new sustainable drainage system to support over-capacity sewers, according to a new draft report led by the Mayor of London.
The Mayor Boris Johnson, in partnership with Thames Water, the Environment Agency and London Councils today published the first London Sustainable Drainage Action Plan for consultation, identifying potential flooding hotspots across the city and proposing innovative ways of diverting rain back from the sewers into the soil with rain gardens or green roofs. 

A flooding ‘heat map’ published today shows the areas of London where the sewer network will be at full capacity by 2050, with associated flooding risk.  

17 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 traditional drainage system which is already 150 years old. Without action, in time the capital could be vulnerable to flooding caused even by normal rainfall.

At the same time the Mayor is supporting a much-needed modernisation of the London sewerage system through the construction of the Thames Tideway Tunnel – a major new sewer that will protect the River Thames from sewerage overflows. Bazalgette Tunnel Limited are constructing the Tunnel and 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 a new rain garden in Tower Hamlets, part-funded by the Mayor of London. The site, formerly the dead-end of a public highway which attracted fly-tippers and anti-social behaviour, has now been transformed into a new public space, combining the functions of flood defence and a new cycle route, edible plant gardens and outdoor seating. This approach is backed by Thames Water, who are announcing £20 million funding for similar innovative projects.
The Deputy Mayor for Environment and Energy Matthew Pencharz said: “Sustainable drainage is a win-win for London – reducing flood risk while also increasing the amount of green space in our city, which is great for providing new community spaces, improving air quality and beautifying our streets. We need new sewers like the Thames Tideway Tunnel but cannot keep building them endlessly, which is why sustainable drainage is necessary. Today’s action plan is just part of a wider initiative by the Mayor of London to encourage sustainable development, which is vital to support our city’s population as it continues to grow.”

Thames Water Director Richard Aylard said “We work really hard to make sure our sewers are as empty as possible whenever heavy rain is expected but it’s important we also look at how to reduce surface water getting into them in the first place. We’ve set aside £20 million to help support sustainable drainage projects across our patch over the next five years. Our aim is to help create at least 20 hectares, which is equivalent to about 30 football pitches, of green infrastructure to capture rainwater by 2020.”
Chair of London Councils’ Transport and Environment Committee Cllr Julian Bell said: “Flooding is a very real threat for significant numbers of people in London and London needs a robust and sustainable response to address this now to avoid an even bigger problem in the future. The plan contains some key measures which, if implemented in a timely way and correctly, will be of real benefit. The net increase in London’s green infrastructure will not only make London a better place to live but will also reduce the amount of rainwater entering the sewer system and hence reduce the risk of flooding.”
Deputy Director of London for the Environment Agency Simon Moody said: “The government is allocating £12 million over six years to help London boroughs manage surface flood risk, but these projects alone will not eliminate the threat. The London Sustainable Drainage Action Plan identifies opportunities to manage rainwater sustainably for the benefit of the people, businesses and environment of London. I welcome the consultation and hearing from other organisations about how they can help deliver this ambitious plan.”  

Tower Hamlets Cabinet Member for Environment Cllr Ayas Miah said: “As a borough along the River Thames, it is important that we work with the Greater London Authority, Thames Water, the Environment Agency and London Councils to implement this plan. We are very proud of the transformation that has taken place here at Derbyshire pocket park, offering residents an open space and alleviating some of the flood risk.”


Notes to editors

  • The draft London Sustainable Drainage Action Plan (LSDAP) is being launched for 3 months public consultation from today, and can be found here:
  • Interested parties can submit their responses to the consultation online.
  • The draft LSDAP sets out a range of actions for the major land-use sectors in London: education, housing, transport, health, retail, recreational and other open space, other public sector buildings, commercial offices, industrial and major utilities and agriculture.
  • London is one of a number of major international cities, including New York, Portland, Copenhagen and Melbourne who are using natural ‘green’ infrastructure on their streets and buildings to manage flood risk, reduce pollution in the stormwater that runs off their streetscapes and cool the city. 
  • The Derbyshire Street re-development is one of more than 100 pocket parks the Mayor has built during his two terms across 26 boroughs, helping to turn underused public spaces into miniature oases in all parts of the city. It combines several sustainable drainage elements, including a rain garden, green roofs, permeable paving and planter boxes which include water storage.
  • Many sustainable drainage techniques have a range of wider benefits for London, such as improving the water quality in our rivers and streams, providing attractive areas for people and wildlife, storing water, irrigation, and helping keep the city cool in hot weather. A rain garden, one of these techniques, is a specially-designed green space with plants chosen that are able to cope with heavy moisture levels and the nutrients closely associated with stormwater runoff. The aim is to reduce the intake of traditional stormwater drains through capturing rainwater in the soil, or delaying its journey into the sewerage system.
  • The action plan aims to achieve a 25 per cent reduction in surface water flows in the sewer network by 2040. It recommends how each of London’s key land use sectors, from public buildings to offices to parks can be retrofitted to help manage rainwater. This is a far more cost-effective – and greener – method than building endless new stormwater drains.
  • The flooding ‘heat map’ is available as a separate PDF on request.