Tunnel vision: Wavin's AquaCell system being installed beneath the surface of what will become a car park in a housing development. -ContributedDRAINING URBAN areas so that run-off mimics nature instead of providing shock floods is becoming a pressing issue given the increasing frequency of storms throughout the world.
But this is a complex issue. Sustainable urban drainage systems - or SUDs for short - can potentially provide a solution for a key climate change effect such as flooding caused by increased rainfall.
As SUDs mimic nature in enabling water to sink into the ground rather than running off impermeable surfaces into rivers or drains, they are seen as a way of ameliorating an otherwise intractable problem.
The water industry in England and Wales is keen to get the issues resolved at the outset, in case the government is obliged to step in to say who will clean-up pollution.
UK companies are coming up with innovative solutions that are leading the world in providing sustainable drainage solutions.
The Construction Industry Research Association (CIRIA) is a major player in research into SUDs. Ciria's new SUDs web site (www.ciria.org.uk/suds) runs through the different types of SUDs available and gives advice on their use. There is also a glossary of terms and case studies.
One famous example is Wessex Water's headquarters in Bath, western England, that uses permeable paving in the car parks, porous blocks that filter through to soakaways and permeable grass paviors through which run-off filters into pipes and a storage tank.
A swale runs down the western edge of the site and this also drains to the main storage tank. Water from the tank is pumped back to soakaways at the top of the site and also feeds an ornamental water feature. Roof run-off and treated grey water are stored in three intermediate tanks and this water is used to flush toilets.
CIRIA is providing specific technical guidance in its research project 637 called Source Control Using Constructed Pervious Surfaces - Hydraulic and Structural Performance. This will produce a technical guidance note addressing hydraulic and structural issues.
Some manufacturers are producing systems to help house builders who need to reduce run-off to be allowed to build on sensitive plots of land.
At the IWEX water industry exhibition, Wavin introduced a new stormwater system, Garastor, alongside its award-winning AquaCell stormwater control system. From a concept developed by Bryant Homes, Garastor uses the space under garages as storage area for excess water during storms.
It collects stormwater from roofs and drives in a prefabricated storage facility. A simple control unit regulates the inflow and outflow of water so that run-off is released into the traditional drainage system at a controlled rate.
AquaCell is also intended to aid stormwater control - this consists of one metre (m) by 0.5m by 0.4m modules made from recycled polypropylene, in a matrix framework that gives a void to solid ratio of 95 to five per cent.
The units clip together in layers to provide a robust infiltration basin that can be wrapped with a permeable geotextile to permit controlled release of water or an impermeable geomembrane so that it becomes a sealed storage unit.
And, UK engineering consultancy WS Atkins is looking at schemes encompassing environmental assessment master planning, flood alleviation, foul drainage, water supply, storm drainage, and other utilities' supply and is incorporating the latest SUDs techniques in large housing and mixed developments.
Atkins is also providing expert advice to the regulators. For instance, it has provided support to the Environment Agency, giving guidance on the regulatory implications of the use of SUDs. And at Tue Brook in Liverpool, Atkins was commissioned by the agency to provide an innovative large-scale SUDs solution for pollution remediation of a severely contaminated, culverted urban watercourse.
LPS
