Understanding and assessing flood risk

You will need to include a sustainable drainage strategy with your planning application (including outline applications) if your development:

• could affect drainage on or around the site
• in an area at risk of flooding¹ such as Flood Zone 2 or 3, or at risk of surface water flooding

If you do not include sustainable drainage systems (SuDS) in these circumstances, you will need to provide the LPA with clear evidence of why their use would be inappropriate.

Your SuDS should be designed in accordance with the National standards for sustainable drainage systems². You should consider local planning policies and guidance on SuDS and provide all the information set out in local lists of information requirements, local SuDS templates, and in What information on sustainable drainage needs to be submitted with a planning application?³ You can put it in a separate document or in the FRA.

To ensure an acceptable standard of operation for the lifetime of the development, SuDS for major development will need to have: 

• appropriate minimum operational standards 
• maintenance arrangements

More information on multifunctional benefits can be found in What are sustainable drainage systems and why are they important?⁴

1. https://www.gov.uk/guidance/flood-risk-and-coastal-change#areas-at-risk-of-flooding
2. https://www.gov.uk/government/publications/national-standards-for-sustainable-drainage-systems/national-standards-for-sustainable-drainage-systems-suds
3. https://www.gov.uk/guidance/flood-risk-and-coastal-change#para59
4. https://www.susdrain.org/delivering-suds/using-suds/background/sustainable-drainage.html