National flood risk standing advice for local planning authorities

For some developments you must consult one or both of :

• the Environment Agency
• the lead local flood authority (LLFA)

For other developments you must use the flood risk standing advice in this guide. This guide applies to the following application types:

• full
• outline
• reserved matters
• change of use
• prior approval for flood risk under certain permitted development rights
• permission in principle
• technical details consent

You must also consult the Environment Agency on a range of other issues. These are set out in Schedule 4 of the Development Management Procedure Order, 2015 (DMPO).

Other risk management authorities may also ask you to consult them. For example:

• the Internal Drainage Board (IDB) when development is in an internal drainage district (IDD) – see the map of IDDs
• the water and sewerage company when sewer flooding may be an issue – check to find the water and wastewater provider

Research the development site

• use the Environment Agency flood map to find if the development is - in flood zone 1, 2 or 3 - within 20 metres of a main river or a flood defence - in a water storage area
• find out whether the development is in an area with critical drainage problems. Note these are currently only designated in Devon and Cornwall. Contact the Environment Agency if you are unsure
• check your SFRA to find out if the development is - in flood zone 1 now but will be at risk of flooding from rivers or the sea during its lifetime - in flood zone 3b (functional floodplain) - at risk from sources of flooding other than rivers or sea
• establish the site area and check the development class
• find out the vulnerability classification.
• use the following guidance to work out whether you need to consult or follow the standing advice.

Check the development class

Major development involves one or more of the following:

• providing 10 or more dwellinghouses defined in article 2 of the DMPO or, where the number of dwellinghouses is not known, the site area is 0.5 hectares or more
• providing a building or buildings where the floor space to be created by the development will be 1,000 square metres or more
• development on a site of 1 hectare or more
• the winning and working of minerals or the use of land for mineral - working deposits
• waste development

A minor development is:

• development of an existing dwellinghouse, or development within the curtilage of a dwellinghouse, for any purpose incidental to the enjoyment of the dwellinghouse
• an extension to an existing building used for non-domestic purposes where the floor space created by the development does not exceed 250 square metres
• alterations to an existing building which do not increase the size of the building

Non-major development is any development not falling into the major or minor development classes.

Check if a flood risk assessment is needed and if one is provided

Before you validate your application, you must check if a flood risk assessment (FRA) is needed and if one is provided.

A FRA is required for all development:

• within flood zones 2, 3 or 3b
• within flood zone 1 with a site area of 1 hectare or more
• within areas with critical drainage problems
• within flood zone 1 where your SFRA shows it will be at increased risk of flooding during its lifetime
• that increases the vulnerability classification and may be subject to sources of flooding other than rivers or sea

Check if information on sustainable drainage systems is needed and if it is provided

Before you validate your application, you must check if a sustainable drainage strategy is needed and if one has been provided.

A sustainable drainage strategy is needed for all:

• major development with surface water drainage
• development with surface water drainage in an area at risk of flooding such as flood zones 2 or 3, or at high risk of surface water flooding

The Sustainable Drainage System (SuDS) will need to provide benefits for:

• water quantity
• water quality
• biodiversity
• amenity

The sustainable drainage strategy will need to include all the information set out in What information on sustainable drainage needs to be submitted with a planning application? The strategy could be a separate document or part of the FRA, where relevant.

For major development, the SuDS will also need to provide multifunctional benefits, where possible. More information on multifunctional benefits can be found in What are sustainable drainage systems and why are they important?

Check to see if you (or the LLFA) have local guidance on SuDS with additional information requirements.

The sequential and exception tests

When the sequential test is needed

A sequential test is required for major and non-major development (check the development class section above) if it is:

• in flood zone 2 or 3
• in flood zone 1 and your SFRA shows it will be at increased risk of flooding during its lifetime
• subject to sources of flooding other than rivers or sea

A development is not exempt from the sequential test if a flood risk assessment shows the development can be made safe throughout its lifetime without increasing risk elsewhere.

See what the aim of the sequential approach is.

When development is exempt from the sequential test

A development is exempt from the sequential test if it is a:

• householder development like residential extensions, conservatories or loft conversions
• small non-domestic extensions with a footprint of less than 250 square metres
• change of use (except changes of use to a caravan, camping or chalet site, or to a mobile home or park home site)

A development is also exempt from the sequential test if it is a development on a site allocated in the development plan through the sequential test and: 

• the proposal is consistent with site’s allocated use 
• there have been no significant changes to the known level of flood risk to the site, now or in the future, which would have affected the outcome of the test 

You may not need a sequential test if development can be laid out so that only elements such as public open space, biodiversity and amenity areas are located in areas at risk of any source of current or future flooding.

How to apply the sequential test

You should speak to the applicant early to discuss the sequential test and determine an appropriate area of search for the test. You should consider whether the test is passed, with reference to the information you hold on land availability. 

You may also need the applicant to: 

• include information to identify any other ‘reasonably available’ sites that you have not already identified - this could include sites currently available on the open market  
• check on the current status of alternative sites to determine if they are ‘reasonably available’ - refer to guidance on Applying the sequential test to individual planning applications 

The exception test is needed for development with a vulnerability classification of: 

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

How to apply the exception test

Refer to:

• what is the exception test?
• when should the Exception Test be applied to planning applications?
• how can it be demonstrated that wider sustainability benefits to the community outweigh flood risk?
• how can it be demonstrated that development will reduce flood risk overall?

The applicant needs to provide the evidence you need to check if both parts of the exception test have been satisfied.  

You should refuse permission if the sequential and exception tests, where relevant, are not done or not satisfied.

When to consult the lead local flood authority

For major development with surface water drainage, you must consult your LLFA.

For other developments with surface water drainage, you should check if there is:

• a local consultation arrangement with your LLFA
• local guidance on SuDS you should follow

For developments that will increase the vulnerability classification and where your SFRA shows it is at risk from other sources of flooding:

• make sure the applicant provides a FRA
• check if there is a local consultation arrangement with your LLFA
• ask your LLFA if you should consult it

When to consult the Environment Agency or follow standing advice

Flood zone 1

When to consult the Environment Agency

You must consult the Environment Agency if the proposed development (including change of use) is:

• within 20 metres of a main river
• in an area with critical drainage problems, other than minor development - check the development class section above

When to follow standing advice

Check your SFRA to see if the site will be at increased risk of flooding from rivers or the sea in future. If it will be, you should:

• make sure a FRA is provided
• apply this guidance as if the site were in flood zone 2

Flood zone 2

When to consult the Environment Agency

You must consult the Environment Agency if the proposed development is within 20 metres of a main river (including culverted main rivers). This includes change of use and minor development - check the development class in the above section. 

You must also consult the Environment Agency if the development will have a vulnerability classification of: 

• ‘essential infrastructure’
• ‘highly vulnerable’
• ‘more vulnerable’ and it’s a landfill, waste facility site, caravan or camping site
• ‘less vulnerable’ and it’s a waste treatment site, mineral processing site, water treatment plant, or sewage treatment plant

This includes change of use but excludes minor development - check the development class in the above section.

When to follow standing advice

You must refer to standing advice for vulnerable developments when the proposed development (including change of use) will have a vulnerability classification of: 

• ‘water compatible’ - including essential accommodation within a water compatible development 
• ‘more vulnerable’ - and not a landfill, waste facility site or a caravan or camping site 
• ‘less vulnerable’ - and not a waste treatment site, mineral processing site, water treatment plant, or sewage treatment plant 

Refer to advice for minor extensions for householder or non-domestic extensions with a floor space of no more than 250 square metres.

Flood zone 3 or 3b

When to consult the Environment Agency

You must consult the Environment Agency on:

• development (including change of use) proposed within 20 metres of a main river or flood defence
• development other than minor development (check the development class in the above section)

Changes of use where the vulnerability classification will:

• be ‘more vulnerable’ or ‘highly vulnerable’
• change from ‘water compatible’ to ‘less vulnerable’

When to follow standing advice

Refer to advice for minor extensions for household or non-domestic extensions with a floor space of no more than 250 square metres.

Please note that table 2 of the planning practice guidance states you should not permit development in flood zone 3b if its vulnerability classification will be:

• ‘highly vulnerable’
• ‘more vulnerable’
• ‘less vulnerable’

Tell the applicant about other permits or consents

You should tell the applicant to check if they need a separate permit or consent. They may need one if the development:

• is within 20 metres of a main river, flood defence or flow control structure
• directly affects a watercourse that is not a main river
• involve activity in the floodplain of a main river which could affect flood flow or storage, for example land raising, and potential impacts are not controlled by a planning permission
• are covered by regional flood defence and land drainage byelaws, where these are applicable

If any of these applies to the development, tell the applicant to refer to check if you need permission to do work on a river, flood defence or sea defence. They should do this as soon as possible as it will tell them if they need an extra permit or consent and who to contact.

Applicants can check if their development activity and location are covered by regional flood defence and land drainage byelaws by referring to this statutory guidance.

If there is a watercourse (including culverted watercourses) on or near the development site, you should also advise the applicant to read Owning a watercourse to understand their responsibilities and the rules they need to follow.

In some cases, we may recommend that the applicant applies for planning permission at the same time as other permits or consents. This will help to resolve complex permitting issues at the same time as decision making for the planning process.

Flood risk permits or consents are often needed as well as planning permission. Getting planning permission does not guarantee they will also get a flood risk permit or consent.

What you need to check in an assessment

FRAs should be: 

• appropriate to the scale, nature and location of the development 
• proportionate to the degree of flood risk 

It should contain the information set out in the site-specific flood risk assessment check-list.  

When reviewing FRAs, you should check whether: 

• all sources of flood risk affecting the proposed development now and throughout its lifetime have been assessed 
• the development type is incompatible with the proposed location 
• the measures proposed will make the development safe throughout its lifetime 
• the proposed development will be appropriately flood resistant and resilient 
• the proposed development will increase flood risk elsewhere and, if so, that appropriate mitigation has been included 
• the site has been laid out, so the most vulnerable aspects of the development are located in areas of lowest flood risk 
• any residual risks can be safely managed 
• safe access and escape routes are included where appropriate, as part of an agreed emergency plan 
• the proposed development incorporates SuDS  

You should make sure that any mitigation measures included in the FRA and standing advice are secured in any planning permission using appropriately worded planning conditions. Conditions should list all necessary mitigation measures rather than just requiring implementation of the FRA. For example, finished floor levels shall be set at a minimum level (insert relevant value) metres above Ordnance Datum.