Engineers develop guide to lower flood risk

An engineer studies a bio-retention area -- an artificial meadow established next to a new housing development

An engineer studies a bio-retention area — an artificial meadow established next to a new housing development

A guide that could eventually lead to fewer UK homes being flooded is being developed by engineers and surveyors at the University of Portsmouth.

They are working on developing guidance to increase the use of sustainable drainage, known as SuDS, to reduce the downstream flood risk caused by new developments.

Sustainable drainage slows down the flow of flood water by storing it in wetlands and ponds or through infiltration. Such ‘green infrastructure’ is also thought to make urban areas more pleasant as well as cleaning polluted run-off water.

However, the economic case for sustainable drainage and who pays for the benefits is more difficult to identify compared to piped drainage, which can be a hurdle to their use.

Dr John Williams

Dr John Williams

Dr John Williams, an expert in environmental technology, and colleagues from the School of Civil Engineering and Surveying at Portsmouth, are developing a toolkit for measuring a range of costs and benefits of incorporating sustainable drainage in new housing developments.  It will give council planners, engineers, surveyors, water companies and those buying houses clear guidance on how to value environmental sustainability being included in new developments.

Dr Williams was awarded £100,000 funding by the Natural Environment Research Council (NERC) for the two-year project.

He said: “Recent flooding has seen many calls for the impacts of new developments on downstream flood risk to be managed through the use of sustainable drainage.

“There is no clear professional guidance available on valuing sustainable drainage systems. Ponds, wetlands and grass ditches slow the flow of water compared to pipes, they create a better urban environment, better habitats and cleaner rivers.”

A new housing development which includes sustainable drainage in the form of a detention basin

A new housing development which includes sustainable drainage in the form of a detention basin

Piped drainage is adopted by water companies and funded through water bills. How green infrastructure is adopted less well defined.

“How do we put a price on these environmental improvements or having more green open space in developments?” Dr Williams said. “Will people be prepared to pay more for a house in a development where some land has been given over to a pond or wetland? There is a therefore a great deal of economic uncertainty in the construction and maintenance of sustainable drainage and the government has recently withdrawn legislation introduced after the 2007 floods, aimed at making the adoption process clearer.”

Experts in the School of Civil Engineering and Surveying will be working with project partners the Royal Institution of Chartered Surveyors and Hampshire County Council, Southern Water, First Wessex, Atkins Global, the Environment Agency and Defra.

A swale -- a constructed grass lined channel which helps manage high levels of water and also helps clean the pollutants of road run-off water

A swale — a constructed grass lined channel which helps manage high levels of water and also helps clean the pollutants of road run-off water

Together, they will assess the capital and life costs of sustainable drainage systems, the benefits to the environment, buyers, water companies and developers. They aim to produce a guide allowing planners and developers to estimate the costs to individuals and the environment of incorporating sustainable drainage in developments in a standardised way.

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