T12: Flooding

The predicted impacts of climate change on flood risk are now acknowledged to be an essential issue that needs to be considered through the planning system. This affects not only the coastal fringe, where low-lying areas will be increasingly vulnerable to rising sea levels and storm events, but also inland areas where more extreme events and a greater intensity of rainfall will increase the incidence and risks arising from river and urban flooding. What may appear an acceptable risk for the short term may be less so several decades in the future, due in large part to the anticipated impacts of climate change.

Under current national guidance new developments, and particularly large scale development schemes, must formally consider and address issues relating to flood risk. A development proposal may be vulnerable to flooding itself, but also if implemented may exacerbate risks elsewhere, now or in the future, and hence all aspects of flood risk must be adequately scoped, assessed, and dealt with.

This Topic Paper provides information and signposting in respect of: 

• Different types of flooding and their potential impact, including reference to the importance and impact of projected climate change
• The key stakeholders involved in flooding matters, their roles and responsibilities in the planning and development process;
• The strategic policy basis, specifically Planning Policy Statement 25 “Development and Flood Risk” (PPS25) and the accompanying Practice Guide 
• The process for assessing flood risk, with reference to the role and purpose of the sequential and exception tests; 
• Managing flood risk at the site-wide level, including the use of Sustainable Urban Drainage Systems, and 
• Managing impacts at the individual building level through design and construction.