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
• is 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. The Environment Agency has worked with CIRIA and the Association of SuDS Authorities to prepare templates to help increase the chances that you include the right information on SuDS first time. You should select the template that best fits the scale of your development:

• SuDS Strategy Template for Major development³
• SuDS Strategy Template for Non-major development⁴

You should also consider relevant local planning policies and guidance on SuDS and provide all the information set out in local lists of information requirements, and in What information on sustainable drainage needs to be submitted with a planning application?⁵ 

If you are also producing an FRA you can include SuDS information in the FRA or a separate document.

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?⁶

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://ecab.planningportal.co.uk/uploads/ea/Environment-Agency_SuDS-Strategy-Template_Major.docx
4. https://ecab.planningportal.co.uk/uploads/ea/Environment-Agency_SuDS-Strategy-Template_Non-Major.docx
5. https://www.gov.uk/guidance/flood-risk-and-coastal-change#para59
6. https://www.susdrain.org/delivering-suds/using-suds/background/sustainable-drainage.html