SC120003 - Managing urban flooding from heavy rainfall - encouraging the uptake of designing for exceedance

Theme:Sustainable Asset Management
Project status:Completed
Start date:01/10/2012
End date:27/07/2014
  • land use planning,
  • flood storage,
  • Sustainable Development,
  • Health,
  • civil engineering,
  • safety and risk,
  • engineering and construction


Urban areas may flood from time to time. Making our urban drainage systems big enough to cope with every rainfall event is unsustainable. We can choose to let flooding impact on communities or we can choose to manage it. If we manage excess water at surface level that our urban drainage cannot take, we can reduce the impacts, even if it occasionally causes disruption. Using highways, kerbs, and open spaces to channel, direct and store surface water is called “designing for exceedance”.

In 2006 a good practice guide on designing for exceedance Designing for exceedance in urban drainage – good practice (CIRIA C635) was published.  It has been difficult to assess the uptake of the guidance and impact on delivery, and there have been a number of other initiatives since publication, especially with regard to using roads as exceedance pathways and retrofitting.  

The objective of this project was to investigate new approaches, assess uptake, showcase and disseminate good practice helping to develop a compelling business case for designing for exceedance. The work also provided recommendations on how delivery can be further improved and encouraged.  

This project has collated a series of case studies, identified critical success factors and produced recommendations to improve stakeholder collaboration and wider acceptance of the principals behind designing for exceedance. These can be downloaded from the external links tab on this page.