Understanding and assessing flood risk
Check if the sequential and exception tests apply
A sequential test1 is required for major and non-major development – (check the development class section above) if it is:
- in flood zone 2 or 3
- in flood zone 1 and your LPA’s SFRA shows it to be at risk of flooding from rivers or the sea in the future
- at risk of flooding from other sources, or could be in the future
The sequential test compares your proposed site with other available sites. Its aim is to steer new development to areas with the lowest risk of flooding.
Development in flood risk areas is only exempt from the sequential test if it is a:
- householder development like residential extensions, conservatories or loft conversions
- small non-domestic extensions with a footprint of less than 250 square metres
- change of use (except changes of use to a caravan, camping or chalet site, or to a mobile home or park home site)
- development on a site allocated in the development plan through the sequential test, and the proposal is consistent with site’s allocated use
You should include information with your application to justify what area of search has been used to identify lower risk alternative sites. Refer to guidance on Applying the sequential test to individual planning applications.2 Speak to the LPA to find out what further information may be needed on the sequential test.
If the sequential test can be satisfied you need to check if the exception test is also needed. The exception test is needed for developments with a vulnerability classification3 of:
- ‘highly vulnerable’ in flood zone 2
- ‘more vulnerable’ in flood zone 3a
- ‘essential infrastructure’ in flood zone 3a or 3b
You will need to provide the evidence the LPA needs to check if:
- the development would provide wider sustainability benefits to the community that outweigh the flood risk
- the development will be safe for its lifetime taking account of the vulnerability of its users, without increasing flood risk elsewhere
- the development will reduce flood risk overall, where possible
The LPA can refuse planning permission if the sequential and exception tests are not done or not satisfied.