Guidance

Flood risk assessment: local planning authorities

Find out what you need to do and who you need to consult when reviewing flood risk assessments as part of planning applications.

This guidance is for local authorities who need to review flood risk assessments submitted as part of planning applications.

If you’re a local planning authority and you need to complete a strategic flood risk assessment, read the guide on completing strategic flood risk assessments.

Guidance for planning applicants can be found in the guide on completing flood risk assessments.

You must consult the Environment Agency, your lead local flood authority or both on any proposed developments at a higher risk from flooding before making a decision.

For lower-risk developments, you can use the Environment Agency’s flood risk standing advice.

Check if you need to consult

  1. Check the Environment Agency flood map for the flood zone the development is in and its distance from a river.

  2. Find out whether the development is an area with critical drainage problems as notified by the Environment Agency. Contact the Environment Agency if you are unsure.

  3. Establish the size of the development.

  4. Find out whether it’s classed as vulnerable.

  5. Use the following guidance to work out whether you need to consult or follow the standing advice.

Flood zone 1

For major development with surface water drainage, consult your lead local flood authority.

When to consult the Environment Agency

Consult the Environment Agency if the development is:

Flood zone 2

For major development with surface water drainage, consult your lead local flood authority.

When to consult the Environment Agency

Consult the Environment Agency if the development is within 20m of a main river - check the Environment Agency’s flood map.

You also need to consult the Environment Agency for any development, other than minor development, if the development’s flood risk vulnerability is:

  • essential infrastructure
  • highly vulnerable
  • more vulnerable and it’s a landfill or waste facility or is a caravan site
  • less vulnerable and it’s one of the following: land or building used for agriculture or forestry; a waste treatment site; a mineral processing site, a water treatment plant; or a sewage treatment plant

When to follow standing advice

Refer to the standing advice for minor extensions for developments that are household extensions or non-domestic extensions of no more than 250 square metres.

Refer to the standing advice for vulnerable developments for developments that are classed as:

  • water compatible including essential accommodation within a water compatible development
  • more vulnerable and not a landfill or waste facility site or a caravan site
  • less vulnerable and not any of the following: land or building used for agriculture or forestry; a waste treatment site; a mineral processing site; a water treatment plant; or a sewage treatment plant

Flood zone 3

For major development with surface water drainage, consult your lead local flood authority.

When to consult the Environment Agency

Consult the Environment Agency if the development is within 20m of a main river - check the Environment Agency’s flood map.

You also need to consult the Environment Agency for all developments other than a minor development.

You must also consult the Environment Agency for developments involving a change of use and as a result the flood risk vulnerability has either changed:

  • to more vulnerable or highly vulnerable
  • from water compatible to less vulnerable

When to follow standing advice

Refer to the standing advice for minor extensions for developments that are household extensions or non-domestic extensions of no more than 250 square metres.

What you need to check in an assessment

When reviewing flood risk assessments, you should look at:

  • how flood risk affects the proposed development
  • whether the development type is appropriate for the proposed location
  • whether the site’s flood risk is too great for the development
  • whether the proposed development will increase flood risk elsewhere

For developments in zones 2 and 3 you must also check that the applicant has:

  • carried out the sequential test and the exception test where necessary
  • met the additional flood resistance and resilience requirements where necessary

The sequential and the exception tests

Check whether the sequential test and the exception test should have been applied or not.

The applicant needs to do a sequential test if both of the following apply:

  •  the development is in flood zone 2 or 3
  • a sequential test hasn’t already been done for a development of the type the applicant plans to carry out on their proposed site

Sites allocated in the local plan don’t need to have had a sequential test carried out.

The exception test should have been carried out for developments that are:

  • highly vulnerable in flood zone 2
  • more vulnerable in flood zone 3a or essential infrastructure in flood zone 3a or 3b

You must refuse to grant planning application if either the sequential test or the exception test hasn’t been carried out when they should have been.

Extra flood resistance and resilience measures

Check that applicants have followed the extra flood resistance and resilience requirements for developments in flood risk areas where ground floor levels are lower than the estimated flood level for the site.

Water depth up to 0.3m

The building or development must have been designed to keep water out as much as possible. Materials that have low permeability (ie materials that water can’t pass through, eg impermeable concrete) must have been used.

Water depth from 0.3m to 0.6m

The building or development must have been designed to keep water out (unless there are structural concerns) by:

  • using materials with low permeability to at least 0.3m
  • using flood resilient materials (eg lime plaster) and design (eg raised electrical sockets)
  • making sure there’s access to all spaces to enable drying and cleaning

Water depth above 0.6m

The building or development must have been designed to allow water to pass through the property to avoid structural damage by:

  • using materials with low permeability to at least 0.3m
  • making it easy for water to drain away after flooding
  • making sure there’s access to all spaces to enable drying and cleaning

Contact the Environment Agency

Environment Agency

PO Box 544


Rotherham
Yorkshire
S60 1BY