CIRIA discusses sustainable drainage systems and green infrastructure

“Greening grey infrastructure: from innovation to implementation”

CIRIA organised a webinar this week on sustainable drainage systems and the idea of using ‘green infrastructure’ and nature to manage flood risk. The event provided an overview of the current research and applications in this area, highlighted the benefits of green infrastructure and sustainable drainage systems, and included a number of case studies that demonstrated how these ideas have been put into practice.

One such case is a project undertaken by Welsh Water (Dwr Cymru) in Llanelli, South Wales, where sustainable drainage systems have been retrofitted to address both flooding and water quality problems. Welsh Water have also developed a landscaping concept called Rainscape which is designed to manage rainwater in urban environments and is currently being used on urban landscaping projects. Rainscape features a number of ways to catch rainwater and slow down the speed at which it goes into the sewer network, helping to reduce sewer flooding and pollution and the risk of surface water flooding. The methods include grass channels, swales, porous pavements and underground storage boxes. See our news item “Dwr Cymru develops Rainscape” for further details.

CIRIA has published a briefing paper on green infrastructure which provided background information for the webinar and presents an overview on the use of sustainable drainage systems in both rural and urban areas, including practical examples. CIRIA defines green infrastructure as “a strategically planned and delivered network of natural and man-made green (land) and blue (water) spaces that sustain natural processes.” The application of green infrastructure is recognised in government and EU policy and advocated by bodies such as the Landscape Institute.

Green infrastructure incorporates the idea of natural flood management, which the report’s authors define as: “the alteration, restoration or use of landscape features to reduce flood risk.” Its application in rural areas is illustrated by the example of the village of Belford in Northumberland, which failed to satisfy cost-benefit criteria for structural defences despite a number of floods occurring in recent years. Natural flood management techniques were used as an alternative, including a number of “run off attenuation features.” Put simply, says CIRIA, “the design philosophy is to create features that slow, store and filter run off in the rural landscape.” The methods include ‘offline’ diversion ponds, where water is diverted from a stream network into a pond structure for temporary storage, permeable timber barriers, and ‘online’ ditch management. For more details, see “Using green infrastructure and nature to manage flood risk”.


1. CIRIA is the Construction Industry Research and Information Association. It is an independent, not-for-profit association whose aim is to link organisations with common interests and to facilitate a range of collaborative activities that help to improve the construction industry. For further information on the recent webinar, see CIRIA events.
2. GeoSmart’s range of Flood Risk and Drainage Reports for developers and property owners include Sustainable Drainage System (SuDS) Assessments. For further information, see our Reports page or give us a call on 01743 298 100.