Put to the test by Oxfordshire’s floods

Oxfordshire County Council is responding to the area’s history of flooding by making sustainable urban drainage systems (SUDS) an integral part of the planning process in developments throughout the county.

It’s a system that’s already been put to the test, explains Barry West, the officer responsible.

The introduction of SUDS into Oxfordshire was inspired by a presentation that Barry West and his colleagues at Oxfordshire County Council saw in the mid-1990s.

‘The presentation, at Coventry University, explained the concept of “dealing with rain where it falls” and this really struck a chord with us,’ West, the highways adoption officer for Oxfordshire, says. ‘We went away inspired to put the SUDS concept into practice.’ After collating research from Scotland, Europe and Australia and presenting their ideas to the director of the department, the team was given the green light to promote the approach across Oxfordshire.

Clear communication

West emphasises the importance of communication to the planning and development of SUDS. ‘You need to get all the stakeholders around the table from the very beginning and bring in experts from a range of fields,’ he says.

‘The benefits must be clear to everyone involved if sustainable drainage is to become an integral part of the development. There’s also a lot of good practice out there that you can learn from in order to give your project the best possible chance of success.’

Putting SUDS into practice

Since the introduction of the SUDS approach, developments in Oxfordshire have featured a range of alternatives to traditional drainage, such as balancing ponds, wetlands and swales. Each development aims to make sustainable drainage into an attractive feature that can also bring additional benefits such as increasing biodiversity or introducing traffic calming measures.

All major development schemes in Oxfordshire now have design guides that incorporate SUDS from the outset and clearly demonstrate how sustainable drainage contributes to the quality of place. As of January 2008 SUDS are integrated into all new road building.

One example is the SUDS at Hanwell Fields in Banbury. Swales at the top of the site filter water through a series of ditches with rocks that oxygenate the water, then into reed beds and wetlands. The site provides a recreation amenity, with boardwalks making the space highly accessible, and promotes biodiversity. The council and the developer both contribute to its maintenance.

In smaller developments, the council insist that all roads are built using porous surfacing. Block paving systems support sustainable drainage. The council included this requirement in the specification that the developer would need to meet for the road to be adopted.

‘The developer claimed that the porous surfacing would add to the costs, but a block paving system does away with the need for pipe work, gullies and manholes,’ explains West. ‘When tarmac fails you have to throw it away, but with a paving system you only need pull up the blocks, repair the layer underneath and replace them. This means that it’s no more expensive in the long run. We’ve got block paving still performing well after 10 years.’

Integrated teams

Team working is an essential part of Oxfordshire’s SUDS projects. ‘Our large developments involve integrated teams, often bringing together professionals from highways, planning and engineering with developers, contractors and other stakeholder groups, such as the Environment Agency, education, health practitioners, parish councils and the police,’ explains West.

He also emphasises the importance of establishing a positive working relationship with developers, contractors and suppliers. ‘Spending time talking to developers and contractors is incredibly useful. For example, we’ve worked with contractors to improve existing paving systems and bring innovations to the market.’

Future plans

The SUDS introduced in Oxfordshire have proved highly successful. During the 2007 summer floods and those in February, June and July 2008, none of the porous paved roads flooded. The SUDS approach has been effective with all soil types across the county, from clay to chalk, by slowing down run-off through percolation, transpiration and evaporation.

West and his colleagues are strong believers in the SUDS approach and spend time educating fellow professionals and members of the public about SUDS and how they work. They have also contributed to the CIRIA local authority network on drainage and flood risk management by promoting best practice, helping other authorities and hosting international study tours.