Culvert, screen and outfall manual - New CIRIA guidance


There are hundreds of thousands of culverts across the UK providing a means for railways, highways, canals, footpaths etc. to cross watercourses. Some of these culverts also have screens for security purposes or debris management. There are also numerous highway drainage outfalls.

Culverts, screens and outfalls are superficially simple structures, but they have the potential to restrict flow (causing flooding), can be more expensive to maintain than open channels or soakaways, and can adversely affect the aquatic environment and create new health and safety hazards. As a result, there is a presumption against the construction of new or replacement culverts.

Assessment of the hydraulic performance of a culvert, screen or outfall can be complex. This manual provides a number of methods from hand calculation to computer modelling to assist.

In service, a well-designed culvert or outfall may require little attention from an asset manager other than routine inspection and maintenance. It should also not require a screen. However, there are thousands of existing culverts, screens and outfalls across the UK, many where conditions have been significantly altered by urban development, climate change and concern about the quality of the natural environment. Problems of decaying structural fabric, sedimentation, blockage by debris, and inadequate capacity present an asset manager with a constant demand for assessment, rehabilitation, repair and enhancement. Also, there are increasing environmental and potential liability pressures, driven in part by legislation, that require asset managers to examine options for improving the environmental, hydraulic and health and safety performance of culverts, screens and outfalls, including restoring the watercourse back to a more natural state by means of ‘daylighting’ and removal of screens that are no longer necessary.

This event will provide an overview of how the new manual will help understand, consider and address the above challenges.

It will also provide information on how to download this free manual.

This  CIRIA project was funded  by the Environment Agency, Network Rail, Highways England, Transport Scotland and written under contract to CIRIA by JBA Consulting and Mott MacDonald.

Culvert, screen and outfall manual - Launch webinar