University of Salford Manchester

New method makes life easier for drainage engineers

Friday 6 July 2012
Drainage site with pond and greenery
An illustration of a brownfield site after drainage measures have been implemented.
Following a survey of more than 100 sites across Greater Manchester, a University of Salford academic has developed an easy-to-use toolkit for determining the best systems to reduce the risk of flooding.

Designed for engineers who are seeking to address the Defra Overarching Impact Assessment for the Natural Environment White Paper, the toolkit gives 17 variables, which are applied onsite to provide outcomes affecting not only drainage results but also social, economic and cultural factors.

Professor Miklas Scholz’s unique tool proposes the retrofitting of sustainable drainage systems (SuDS) using techniques that obtain the highest ecosystem services for specific urban sites. This approach is based on a new philosophy adapted to SuDS rather than on traditional engineering judgements based on quick community and environment assessments.

The retrofitting of SuDS is currently undertaken ad hoc using expert experience supported by minimal guidance based predominantly on hard engineering variables such as rainfall amount, hydraulics and ground permeability.

As a result, there is a lack of practical decision-making tools useful for a rapid assessment of the potential of ecosystem services when retrofitting SuDS in urban areas.

The tool developed at the University of Salford goes beyond the capabilities of established methods developed by the Construction Industry Research and Information Association (CIRIA) by including all ecosystem services criteria and relying less on engineering experience.

In Greater Manchester, a comparison with the traditional CIRIA approach of determining community and environment variables indicated that ‘hard’ SuDS techniques such as permeable pavements and below ground storage tanks are relatively more appropriate than ‘softer’ options such as infiltration trenches, soakaways and infiltration basins for a lot of sites.

“It was surprising that intuitively less sustainable SuDS techniques received relatively high scores,” said Professor Scholz. He explained this by the holistic and multi-disciplinary nature of his novel ecosystem services approach for SuDS retrofitting.

Professor Scholz concluded: “We hope that our proposed decision-support tool is likely to lead to structural changes of SuDS, which will transform the urban landscape and reduce the risk of flooding. Ecological retrofitting will be beneficial for humans and the environment.”

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