Advice on planning application supporting documents

Policy 35 of our City Plan 2019-2040 sets out our approach to managing flood risk in Westminster.

Flood risk assessments

If your application is for a property in a flood risk zone or surface water management zone, a flood risk assessment (FRA) may be required, as set out in our validation checklists.

You can use the interactive policies map to check if you are in a flood risk area or surface water management zone.

The Environment Agency has also published advice for FRAs. For residential and non-residential extensions of less than 250 square metres in Flood Risk Zones 2 and 3, visit GOV.UK for advice.

If your application does require an FRA, you may need to contact a consultant to prepare it for you.

Sustainable drainage systems (SuDs) strategies

Major applications and some non-major applications (where appropriate) must be accompanied by a sustainable drainage strategy. To show how your major development complies with Westminster and national planning policy, you should submit the drainage pro forma with your sustainable drainage strategy at the time of validation.

To fill in Westminster's proforma, please see the London Sustainable Drainage Proforma website.

You can use these tools to help design and evaluate sustainable drainage systems.

Further advice on flood risk and requirements can be found in our Environmental SPD:

Strategic Flood Risk Assessment

Our Strategic Flood Risk Assessment (SFRA) 2023 is intended to provide an assessment of all sources of flooding required for consideration under the National Planning Policy Framework (NPPF) within Westminster, taking into account the impacts of climate change.

The SFRA assesses the impact that land use changes and development in the area may have on flood risk. It also sets out a number of approaches to avoid, reduce, mitigate and manage this risk as part of a wider objective to ensure sustainable development.

Flood risk strategies and further advice

We have included further guidance below on when FRAs and drainage strategies are required for new developments. The guidance is in accordance with the NPPF.

Further details about what should be included in an FRA and drainage strategy are included in the following checklists:

Major planning applications:

Non-major planning applications, which includes:

• new development for 1-9 dwellings
• new commercial development over 100m2
• extensions/alterations which would alter the footprint over 100m2
• all basement development
• other developments that include a change of use to an increased vulnerability class

Small-scale planning applications, which includes:

• no change of use to increased vulnerability class
• alterations or other works which do not increase building footprint or levels, e.g. changes to windows
• extensions/alterations which would alter the footprint to less than 100m2

You may also need to refer to the following:

• Planning practice guidance for information on flood risk and coastal change
• Mayor of London's Regional Flood Risk Appraisal
• Mayor of London's surface water flooding advice
• London Sustainable Drainage Action Plan
• Construction Industry Research and Information Association (CIRIA) SuDS Manual
• Defra Non-Statutory Technical Standards for SuDS