Guidance

Flood risk assessment for planning applications

Find out when you need to do a flood risk assessment as part of your planning application, how to do one and how it's processed.

As a planning applicant, you may need to carry out a flood risk assessment for your proposed development site.

Guidance for local planning authorities can be found in the guide on reviewing flood risk assessments.

You’ll usually need to pay a flood risk specialist to carry out the flood risk assessment for you, but you may be able to do it yourself if it’s for a simple, low risk development, eg a house extension. If you’re unsure, contact the Environment Agency for advice.

Your planning application may be refused by your local planning authority if you don’t include a flood risk assessment or if it isn’t satisfactory.

When you need an assessment

You need to do a flood risk assessment for most developments within one of the flood zones.

This includes developments:

  • in flood zone 2 or 3 including minor development and change of use
  • more than 1 hectare (ha) in flood zone 1
  • less than 1 ha in flood zone 1, including a change of use in development type to a more vulnerable class (eg from commercial to residential), where they could be affected by sources of flooding other than rivers and the sea (eg, surface water drains, reservoirs)
  • in an area within flood zone 1 which has critical drainage problems as notified by the Environment Agency

Find out what flood zone you’re in

Contact your local planning authority to check if your development site is in an area identified as having critical drainage problems.

When you don’t need an assessment

You don’t need to do a flood risk assessment for a development that’s less than 1 ha in flood zone 1 unless it could be affected by sources of flooding other than rivers and the sea, eg surface water drains.

When to follow standing advice

You should follow the Environment Agency’s standing advice if you’re carrying out a flood risk assessment of a development classed as:

  • a minor extension (household extensions or non-domestic extensions less than 250 square metres) in flood zone 2 or 3
  • ‘more vulnerable’ in flood zone 2 (except for landfill or waste facility sites, caravan or camping sites)
  • ‘less vulnerable’ in flood zone 2 (except for agriculture and forestry, waste treatment, mineral processing, and water and sewage treatment)
  • ‘water compatible’ in flood zone 2

You also need to follow standing advice for developments involving a change of use into one of these vulnerable categories or into the water compatible category.

How to do an assessment

Read the guidance for:

The Planning Practice Guidance has a checklist that you may find useful when preparing your flood risk assessment.

Contact the Environment Agency

Environment Agency

PO Box 544


Rotherham
Yorkshire
S60 1BY