With the wettest April on record causing extensive flooding throughout the southern half of the country, many are wondering why there was still a severe drought – and hosepipe bans — in the same areas at the same time. Sustainable Drainage Systems (SuDS) and techniques such as concrete block permeable paving are an essential part of the solution but they must be applied extensively to have real impact, says Interpave.

Much of the recent flood and drought problem can be attributed to the sealing-up of our urban areas with buildings and impermeable hard surfaces, directing rainwater straight into sewers and rivers. This quickly causes downstream flooding and pollution but also prevents the recharging of severely depleted ground water. SuDS and concrete block permeable paving maximise opportunities for rainwater to infiltrate into the ground, eliminating or reducing the amount that leaves site and feeding local aquifers. Even where ground conditions limit infiltration, SuDS can attenuate any runoff by storing and slowing flows during rainfall.

These issues are well-understood — following reports on similar flooding in 2007 — and government is finalising measures to address them, including requirements for SuDS. But there are also proposals for a ‘get-out’ clause, where developers could avoid applying SuDS for cost reasons – even though SuDS generally offer a more cost-effective solution. Universal, not sporadic, application of SuDS is essential to impact on the prevention of downstream flooding and pollution. Critical mass is essential for SuDS in the urban environment and there is no room for exceptions.

The trade association Interpave has been involved in the development of permeable paving technology for SuDS from the start and provides a comprehensive and definitive information resource, including case studies and technical guidance, via www.paving.org.uk. Interpave also supports the National SuDS Conference on 20-21 June this year. The Conference is intended to bring together the experience of those already implementing SuDS around the country and aims to consolidate guidance in the context of the 2010 Flood and Water Management Act and related draft National Standards. More information is available at www.sudssource.org.