Culverts are one of the most common types of drainage infrastructure and are widely used by many sectors and organisations in the UK. There are tens of thousands of culverts currently in operation, many of them over 50 years old and requiring significant repairs or replacement. Although the construction of new culverts is discouraged, there are many situations where there is no viable alternative, so significant numbers of new culverts are still being designed and constructed each year. Together, these culverts represent a huge asset which has to be managed to achieve best value and performance.
The original Culvert design manual (CIRIA R168, 1997 reprinted 2003) has sold over 500 copies since 1997, demonstrating a high uptake from stakeholders and the importance of the document for the industry. Since this time there have been significant changes in drivers and policy, as well as design and management practices. The increased occurrence of floods in the past decade, and in particular the increased risk of surface water flooding (as identified in the Pitt Review of the Summer 2007 flooding), have highlighted inadequacies in the hydraulic performance of culverts, which form an important element of urban drainage systems. It can be expected that there will be a steady increase in flooding incidents in which culverts are implicated as climate change effects become ever more significant.
Furthermore, increased storminess as well as land use changes are together likely to result in greater sediment and debris loads in streams and drainage channels, as high winds and flash flows tend to generate an increase in trash and debris entrained in the flow. This material has the potential to block culverts and obscure trash and security screens, increasing the probability of localised flooding. The removal of sediment from culverts also presents an expensive, hazardous and often difficult maintenance need which can be reduced by improved design and/or management approaches.
All of the above have huge implications for both the design and construction of new culverts and, perhaps more importantly, for the management of the thousands of existing culverts, many of which are already experiencing capacity problems. The new Culvert design and operation guide will address all of these issues, and will provide a comprehensive national benchmark for good practice for both designers and asset managers.
This project started June 2008. A consultation workshop is due to be held on 10 September 2008 in Birmingham. For further details please contact CIRIA on the contact details given below.
Environment Agency, Network Rail, British Waterways, Transport Scotland, Tubosider UK Ltd, Highways Agency and Richard Allitt Associates.
A consortium led by Royal Haskoning with Jeremy Benn Associates and Charlie Rickard.
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