FOR IMMEDIATE RELEASE
Heat waves or prolonged periods of drought followed by intense rainfall can cause localised flash flooding. In the event of extreme rainfall, the capacities of sewers, covered watercourses and other drainage systems can be tested to their limits. If drainage capacity is exceeded surface flooding may occur. The excess water (exceedance flow) is conveyed above ground, and will travel along streets and paths, between and through buildings and across open space along the path of least resistance. Indiscriminate flooding of property can occur when this flow of water is not controlled. This is especially problematic where the drain is a combined sewer and sewage flooding can result.
Experience has shown that much of the recorded flooding in urban areas is attributable to the passage of above ground surface flow. However, much can be done to mitigate the effects if surface flood flow is managed proactively. Recognising the importance of flood pathways along highways and other routes, and the storage of water in low spots, is the first step to better management. Through good design, a second important step is to direct flood flows along routes where the risk to health and safety is minimal.
CIRIA’s new guidance Designing for exceedance in urban drainage – good practice (C635) provides advice for the design and management of urban sewerage and drainage systems to reduce the impacts that arise when flows occur that exceed their capacity and explains how systems can be designed to safely and sustainably accommodate excess water during extreme weather events. It aims to improve engineers, planners and designers’ appreciation of the risks associated with urban drainage systems and how these risks may be mitigated.
Designing for exceedance in urban drainage – good practice (C635) is available to buy or download from CIRIA. Visit www.ciria.org or contact CIRIA, Classic House, 174-180 Old Street, London EC1V 9BP. (T) 020 7549 3300; (F) 020 7253 0523; (E) enquiries@ciria.org
ENDS
To request a copy for review, or for further press information, contact James Milne at the above postal address or email: press@ciria.org.
Alternatively, you can download a copy from www.ciria.org/downloads.htm
Authors: David Balmforth, MWH; Christopher Digman, MWH; Richard Kellagher, HR Wallingford; David Butler, University of Exeter.
CIRIA is a member-owned organisation that works with the construction industry, government and academia to provide performance improvement products and services in the construction and related industries. It was founded in 1960 and currently engages with around 700 subscribing organisations.Activities include collaborative projects, networking, publishing, workshops, seminars and conferences. About 40 projects are run at any one time, about 100 events are staged every year, and 25 books published per annum.