SUDS – greening urban drainage

The government’s 2009 UK Climate Change Projections (UKCP09) report confirmed what many people had feared – that over the decades to come, the UK will experience hotter, drier summers resulting in droughts, and warmer, wetter winters bringing more frequent intense storms and a greater risk of flooding. Of the 5.5 million properties in England and Wales at risk of flooding from all sources some 3.9 million are susceptible to flooding from surface water. During the summer floods of 2007, record rainfall caused surface water runoff from roads and built-up areas to overwhelm drainage systems resulting in insurance claims of over £3 billion.
    
We estimate that of the 55,000 homes and businesses flooded, the majority were affected by this surface water flooding. The Environment Agency is working to build sea and river defences to reduce the risk of flooding in coastal and riverside areas, as well as working with professional partners and the public to be prepared for flooding. But planners and developers have an important role to, by including sustainable drainage systems (SUDS) in new developments to reduce the risk of flooding by surface water and to provide other benefits for the environment.

The benefits
The SUDS approach to surface water drainage balances water quality, flood risk and amenity in the design of drainage systems by adopting a sustainable approach to the management of surface water. There are a wide range of SUDS techniques. These include green roofs, rainwater butts, soakaways and permeable paving to manage rainwater locally. These are particularly useful in high-density developments, helping to keep surface water runoff at greenfield runoff rates. Where additional controls are needed, swales, ponds and wetlands are used to carry water, provide storage and improve water quality. These SUDS techniques provide welcome green features in new developments and, alongside green roofs, create valuable habitats for wildlife.
    
The SUDS approach has important benefits for the quality of our streams and groundwaters. By implementing pollution prevention measures as part of the SUDS approach we can minimise the risk of causing water pollution. Controlling rainfall at source helps prevent pollutants being washed from streets and other paved areas into watercourses and reduces polluting storm overflows from sewers. By better managing where rainwater goes, we can help reduce the likelihood of water pollution.

Taking responsibility
In England and Wales, a variety of legislation and guidance applies to the management of surface water, with responsibility shared by local authorities, highways authorities, water companies, internal drainage boards and the Environment Agency. For new developments, planning guidance in both England (PPS25 – Development and Flood Risk) and in Wales (TAN 15) encourage the use of SUDS, as do Building Regulations and the Code for Sustainable Development.
    
Climate change scenarios have highlighted the advantages of the SUDS approach over conventional drainage and we have seen government and public bodies acting to raise awareness of SUDS techniques. Although PPS25 and TAN 15 encourage drainage which mimics natural systems, in practice the historic lack of clarity over ownership and maintenance of SUDS has resulted in developers taking the easier option of using the, automatic right to connect to a public sewer, in most cases.
    
The government’s 2008 water strategy for England, Future Water, highlighted the importance of tackling surface water drainage. It emphasised better management of rainwater and preventing surface water entering inappropriate underground drainage systems. A first step in England has seen individuals planning to pave their front gardens being encouraged to use a SUDS approach by a change to permitted development rights which exempt permeable systems from the need for planning permission.

Early adopters
The Environment Agency has promoted the SUDS approach to drainage for some years and has played a central part in the National SUDS Working Group, which brings together key government departments, the water industry and developers. We work with a range of institutions and developers to improve knowledge on SUDS and are also leading by example; our new head office in Bristol City Centre will have rainwater harvesting to reduce water consumption and surface water runoff. We have also introduced a SUDS training course for our own staff, which is available to local authorities on request. Local authorities themselves increasingly include SUDS information into their policies, and we are now seeing more examples of successful developments incorporating SUDS techniques.
    
In Bristol, permeable paving has been retrofitted in a number of streets close to the city centre as part of a “Home Zones” project in the city. Oxfordshire County Council has pioneered the use of SUDS for streets and other areas in new housing developments across the county. They have emphasised the savings for developers in laying flat, permeable paving, without the need for gullies and associated drainage systems, when negotiating commuted sums for future maintenance.
    
The use of green roofs has also grown. Developers recognise the multiple benefits they offer in addition to attenuating and reducing rainwater runoff. They can help reduce energy use and extend the life of the roof by insulating it and protecting the waterproofing, they can provide valuable habitat or amenity benefits and help reduce the urban heat island effect. Green roofs can be seen on housing developments and commercial sites from Canary Wharf in London to Waverley Gate in the centre of Edinburgh. They have also been widely used in schools.

Floods and Water Bill
At the time of writing the Floods and Water Management Bill is progressing through Parliament and is anticipated to receive Royal Assent during the spring. The Bill contains wide ranging provisions to improve flood risk management and protect water quality and includes important proposals on SUDS.
    
Currently, the Bill contains proposals that mean that all new developments will have SUDS drainage that provides sustainable surface water management and complies with the National Standards. Surface water drainage will require approval by a SUDS Approval Board (SAB) prior to construction and the same body will be able to monitor construction and will need to be satisfied as to arrangements for the adoption and maintenance of the scheme when complete. The SAB will be the county council or unitary local authority in England. In Wales there will also be SABs but it has yet to be determined how they will be formed.

The future for SUDS
SUDS, which provide a sustainable approach to surface water management, will play an important role in how we adapt to the challenges of a changing climate. The Bill, when enacted, will mean that developers know what they have to build and can be sure that surface water drainage arrangements serving new developments will be adopted.
    
The development of the National Standards is challenging, but a successful outcome will mean a rapid move to the use of SUDS being the norm rather than the exception. If we achieve the right balance between water quality, quantity and amenity we could see a major improvement in the appearance of new developments, with drainage integrated into the design from the start.

About the author
Geoff Gibbs is currently a technical advisor for Development and Flood Risk at the Environment Agency. A chartered civil engineer, he has worked in flood risk management for more than 30 years. He has represented the Environment Agency on steering groups that have developed guidance documents on sustainable surface water management practice.
    
For more information
Further information on SUDS for developers can be found at www.environment-agency.gov.uk