Fifteen new projects are to consider how the risk of intra-urban flooding can be reduced, in the face of an expected increase in development and heavy rainfall, by overcoming barriers to its effective management.
The Government pilots are to test whether changes in legislation, regulation and practice by a wide range of bodies are needed to better combat flooding from surface water and urban drainage systems, as consultants have concluded (Surveyor, 4 May 2006). They will bring together local highway authorities, water companies, and the Environment Agency in an attempt to map floodwater pathways from different sources.
Some of the pilots – such as in Lewes and Bradford – will be considering how to avoid a recurrence of major intra-urban flooding events. But the primary focus of many of the selected pilot areas will be to prevent increased flooding from surface run-off and overloaded drains in areas earmarked for development.
The project in Cambourne, Pool and Redruth in Cornwall, for example, will consider the ability of the area’s drainage infrastructure to cope with the building of 6,000 new homes by 2026, almost doubling the existing stock. The Upper Rea project in Birmingham will assess the impact of significant redevelopment, including at the former Rover car plant.
The need to bring together separate models of flooding from different sources – rivers, other watercourses, surface run-off, drains and sewers – will be considered, as will how planning decisions can be influenced to prevent future problems.
A scoping study for the Department for Environment, Food and Rural Affairs by consultant MWH identified a need for planners to make developers consider drainage and flood risk earlier. Councils have been advised that relatively minor features – such as carriageway kerb heights – can ‘significantly affect flood risk’ (Surveyor, 3 November 2005).
More than 70,000 new homes are planned for the ‘Leeds city region’ which includes Bradford. Tony Poole, principal drainage engineer at Bradford council, told Surveyor: ‘We need to pinpoint where surface water collects and flows, and accommodate that within developments.
‘We can’t keep trying to build ever-bigger pipes, there’ll always be finite capacity.’ Studies for the Government predict that rainfall volumes will increase by 40% on average.
The role of private landowners will also be considered by the pilots. Nick Martin, wastewater modelling consultant at Thames Water, which will lead the project in north Brent in London, said: ‘Both changing rainfall patterns and the paving over of gardens are increasing the risk of flooding in the area.’