Flood risk assessments: applying for planning permission
Source: gov.uk (2025-10-22)

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

This guidance is for planning applicants.

Local planning authorities (LPAs) should use the National flood risk standing advice for local planning authorities (https://www.gov.uk/guidance/flood-risk-assessment-local-planning-authorities) when reviewing flood risk assessments.

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

You will usually need to pay a flood risk specialist to carry out a FRA for you. An exception to this may be if it is for a simple, low risk development, for example, a house extension. In this case you may be able to do it yourself. If you are not sure, contact the Environment Agency (https://www.gov.uk/guidance/flood-risk-assessment-for-planning-applications#contact) for advice.

Your local planning authority (LPA) (https://www.planningportal.co.uk/find-your-local-planning-authority) may refuse your application if you do not include a FRA or if it is not satisfactory.

When you need a flood risk assessment

You should complete a FRA for all development (including minor development (https://www.gov.uk/guidance/flood-risk-and-coastal-change#para51) and changes of use) proposed:
- in Flood Zones 2 or 3 or see flood map for planning (https://flood-map-for-planning.service.gov.uk/)
- within Flood Zone 3b
- within Flood Zone 1 with a site area of 1 hectare or more
- within ‘Flood Zones plus Climate Change’, showing it is at increased risk of flooding from rivers or sea in future - see flood map for planning (https://flood-map-for-planning.service.gov.uk/)
- with Flood Zone 1 and the flood map for planning (https://flood-map-for-planning.service.gov.uk/) shows it is at risk of flooding from surface water
- in areas with critical drainage problems
- within Flood Zone 1 where the LPA’s strategic flood risk assessment (SFRA) shows it will be at increased risk of flooding during its lifetime
- that increases the vulnerability classification (https://www.gov.uk/guidance/national-planning-policy-framework/annex-3-flood-risk-vulnerability-classification) and may be subject to sources of flooding other than rivers or sea
When you need a sustainable drainage strategy and what to include

You need to include a sustainable drainage strategy if your application is for development:
- which could affect drainage on or around the site
- in an area at risk of flooding (https://www.gov.uk/guidance/flood-risk-and-coastal-change#planning-and-flood-risk) such as Flood Zones 2 or 3, or at risk of surface water flooding
Your Sustainable Drainage System (SuDS) should be designed in accordance with the National standards for sustainable drainage systems (https://www.gov.uk/government/publications/national-standards-for-sustainable-drainage-systems/national-standards-for-sustainable-drainage-systems-suds).

You should include all the information set out in:
- section 6 of the site-specific flood risk assessment checklist (https://www.gov.uk/guidance/flood-risk-and-coastal-change#para80)
- What information on sustainable drainage needs to be submitted with a planning application (https://www.gov.uk/guidance/flood-risk-and-coastal-change#para59)
Your sustainable drainage strategy can be a separate document or be part of a FRA. Check to see if the LPA or lead local flood authority (LLFA) have local policies or guidance with additional requirements.

Research the development site

To access the right flood risk advice for your development, you need to complete all the following steps:
- use the Environment Agency flood map for planning (https://flood-map-for-planning.service.gov.uk/) to find if the development is in Flood Zone 1, 2 or 3
- use the Environment Agency flood map for planning (https://flood-map-for-planning.service.gov.uk/) to find if the development is at risk of surface water flooding
- use the Environment Agency flood map for planning (https://flood-map-for-planning.service.gov.uk/) and the main river consultation area (https://www.data.gov.uk/dataset/c48935ad-9829-4846-aaf9-a7021ced3e99/main-river-consultation-area) to find if the development is within 20 metres of main river or flood defence
- check the LPA’s SFRA to identify if the site is in Flood Zone 3b (functional floodplain)
- find out the vulnerability classification (https://www.gov.uk/guidance/national-planning-policy-framework/annex-3-flood-risk-vulnerability-classification) - if you are unsure discuss this with your LPA and make it clear in your FRA
- check Table 2 of the Planning Practice Guidance (https://www.gov.uk/guidance/flood-risk-and-coastal-change#table2) to find out if the proposed vulnerability classification is incompatible with the Flood Zone
- check the flood map for planning (https://flood-map-for-planning.service.gov.uk/) and LPA’s SFRA to identify if the site is in Flood Zone 1 now but will be at risk of flooding from rivers or the sea during its lifetime
- check the LPA’s SFRA to identify if the site is at risk from any other source of flooding or it will be during its lifetime
- refer to check the long term flood risk for an area in England (https://www.gov.uk/check-long-term-flood-risk) to identify if your site is at risk of flooding from groundwater (where data is available) or reservoirs
- refer to check the long term flood risk for an area in England (https://www.gov.uk/check-long-term-flood-risk) to identify if your site is at future risk of flooding from surface water (note the time horizon and climate change scenario for surface water fall short of what’s needed for planning so additional assessment may be needed)
- check if the site is in an area with critical drainage problems (https://data.gov.uk/dataset/d10fb8e5-f3af-48c1-a489-8c975b0165de/areas-with-critical-drainage-problems) – these are currently only designated in Devon (https://www.devon.gov.uk/floodriskmanagement/planning-and-development/) and Cornwall (https://www.cornwall.gov.uk/environment/countryside/flood-risk/suds-for-cornwall-guidance/#CriticalDrainageAreas) and the Environment Agency has provided local standing advice for these areas
- establish the site area (in hectares) – the flood map for planning (https://flood-map-for-planning.service.gov.uk/) can help you do this
- check whether the development is major development (https://www.legislation.gov.uk/uksi/2015/595/article/2/made)
- check if your development is a minor extension
- follow the guidance on how to use the flood risk datasets (https://flood-map-for-planning.service.gov.uk/how-to-use-flood-map-for-planning-data) shown on the flood map for planning
A minor extension is a household or non-domestic extension with a floor space of no more than 250 square metres.

In some cases, SFRAs may not hold suitable information for your site on functional floodplain. In such cases, your FRA will need to provide suitable information. To inform your assessment of functional floodplain you could refer to the following information on flood map for planning (https://flood-map-for-planning.service.gov.uk/):
- present day 3.3% annual probability extent of river and sea flooding with defences
- water storage areas
You should always review these datasets to check they are suitable for identifying functional floodplain in each location.

Note that check the long term flood risk for an area in England (https://www.gov.uk/check-long-term-flood-risk) also shows the risk of flooding from rivers and sea. However, this information is different to the Flood Zones shown on the flood map for planning (https://flood-map-for-planning.service.gov.uk/). This means you should not use it for development planning.

Access the right advice

Follow the Environment Agency’s advice for minor extensions (https://www.gov.uk/guidance/flood-risk-assessment-standing-advice#advice-for-minor-extensions) if you are doing a FRA for a minor extension in Flood Zone 2, 3 or 3b.

Follow the Environment Agency’s standing advice for vulnerable developments (https://www.gov.uk/guidance/flood-risk-assessment-standing-advice#standing-advice-for-vulnerable-developments) if you are doing a FRA for a development (including change of use) in Flood Zone 2 classed as:
- ‘more vulnerable’ (https://www.gov.uk/guidance/national-planning-policy-framework/annex-3-flood-risk-vulnerability-classification) - except for landfill or waste facility sites, caravan or camping sites where the Environment Agency should be consulted
- ‘less vulnerable’ (https://www.gov.uk/guidance/national-planning-policy-framework/annex-3-flood-risk-vulnerability-classification) - except for waste treatment, mineral processing, and water and sewage treatment where the Environment Agency should be consulted
- ‘water compatible’ (https://www.gov.uk/guidance/national-planning-policy-framework/annex-3-flood-risk-vulnerability-classification) - including essential accommodation within a water compatible development
You should follow standing advice for vulnerable developments (https://www.gov.uk/guidance/flood-risk-assessment-standing-advice#standing-advice-for-vulnerable-developments) for change of use development in Flood Zone 3 where the vulnerability classification will:
- be ‘water compatible’
- remain unchanged as ‘less vulnerable’
Also follow local flood risk standing advice for development (including change of use) if your site is in an area with critical drainage problems (https://data.gov.uk/dataset/d10fb8e5-f3af-48c1-a489-8c975b0165de/areas-with-critical-drainage-problems) – these are currently only designated in Devon (https://www.devon.gov.uk/floodriskmanagement/planning-and-development/) and Cornwall (https://www.cornwall.gov.uk/environment/countryside/flood-risk/suds-for-cornwall-guidance/#CriticalDrainageAreas). Contact the LPA for a copy of the local standing advice.

For all other development types requiring a FRA in Flood Zones 1, 2, 3 or 3b, you need to follow the advice in Flood risk assessment: Flood Zones 1, 2, 3 and 3b (https://www.gov.uk/guidance/flood-risk-assessment-flood-zones-1-2-3-and-3b)

If your site is in Flood Zone 1 but the flood map for planning (https://flood-map-for-planning.service.gov.uk/) or your LPA’s SFRA shows it will be at increased risk of flooding from rivers or the sea during the development lifetime, you should:
- make sure a FRA is done
- treat the site as if it were in Flood Zone 2 when deciding which advice you need to access
Get information about flood risk from rivers and the sea to help you to complete a FRA

The Environment Agency has information which will help you complete your flood risk assessment.

This includes information on:
- flood risk from rivers and the sea and about flood risk management structures and features
- how climate change will affect flood risk from rivers and the sea in future
- residual flood risk in some locations to help you assess the consequences of flood defences being breached or overtopped
This information will help you calculate the estimated flood level for your site in the design flood (https://www.gov.uk/guidance/flood-risk-and-coastal-change#para2) and assess residual flood risks. Please note that the design flood and residual risks must include an appropriate allowance for climate change (https://www.gov.uk/guidance/flood-risk-assessments-climate-change-allowances).

These products or packages of information are available from the Environment Agency’s flood map for planning (https://flood-map-for-planning.service.gov.uk/):

Product 1

This product is a copy of the flood map which shows:
- Flood Zones 1, 2 and 3
- defences
- statutory main river designations
- water storage areas
Product 3

This product has been discontinued. Relevant information is now available through other products.

Product 4

This product is a detailed FRA map. Where available, it shows:
- detailed flood data
- flood defence locations and attributes
- data on past flood events
- modelled flood levels and extents
- flood defence breach hazard information
The models show the model extents and modelled flood levels and flows at several specific points. This could either be within the river channel or, if available, in the floodplain.

Product 5

This product is a report which includes flood modelling and hydrology reports.

Product 6

This product is the model output data and all the reports in product 5.

Product 7

This product is the Model Input Data, and all the reports in product 5. This represents the best available modelled data we have for the area. You will need to assess any model to make sure it is suitable for your FRA.

Product 8

Flood defence breach hazard information. This information will be included in Product 4 where it is available.

Choose the correct product

For all development you should request product 1 and product 4.

If your FRA will use detailed hydraulic modelling held by the Environment Agency, you are also likely to need products 5, 6 and 7. Refer to Using modelling for flood risk assessments (https://www.gov.uk/guidance/using-modelling-for-flood-risk-assessments) for guidance on when to use modelling and the expected standards.

Some users prefer to view our flood risk information on their own Geographical Information System. The information shown on the Flood Map for Planning is freely available through the Defra Data Services Platform (https://environment.data.gov.uk/dataset/56fb30ae-f20d-490a-9149-a94f3e640261) alongside other relevant flood risk information. The most relevant datasets can be found by searching for ‘development planning’.

Understand limitations of using existing models

Material displayed on the flood map for planning (https://flood-map-for-planning.service.gov.uk/)is provided without any guarantees, conditions or warranties as to its accuracy. This includes maps and risk data. See our terms and conditions (https://flood-map-for-planning.service.gov.uk/terms-and-conditions) for more information.

It’s your responsibility to check the suitability of an existing model for your development.

If you use an existing model from the Environment Agency or another organisation, it is important to check if it:
- represents current risk
- uses the latest available datasets
- complies with current modelling standards
- is at a scale suitable for the assessment you are undertaking
- captures the detail required for a site-specific assessment
- makes use of current climate change allowances
You should be aware that:
- Environment Agency models are not designed to assess third party developments, so do not assume that they are suitable for your proposed development
- even if you use a recent model, you still need to review and possibly update it
- you should provide evidence of any modelling checks and subsequent updates you carry out and record these in the FRA model reporting
- you should refer to the Environment Agency’s standard model and hydrology review templates (https://www.gov.uk/guidance/using-modelling-for-flood-risk-assessments%22%20/l%20%22contact) when carrying out your model review
How to get or order the products

For all the products you need to use the flood map for planning (https://flood-map-for-planning.service.gov.uk/). Find the correct area by entering the postcode or location of the development site. Then you can draw the boundary of your site to get relevant flood risk information.

For product 1, which is a copy of the flood map for planning for your development site, you can download a copy of the map.

For product 4 - input your name and email address on the page for your development site and submit it. The local Environment Agency team will send product 4 information to you for that location within 20 working days.

For products 5, 6 and 7, you need to find the contact details for the local Environment Agency office and send a request to them. You can find these details in the flood map for planning on the page of your chosen development site.

Get information about other sources of flood risk to help you complete a flood risk assessment

You need to consider all sources of flood risk in your FRA. You can get information on surface water flood risk from the flood map for planning (https://flood-map-for-planning.service.gov.uk/). You can get additional information on surface water, groundwater (where available) and reservoir flooding by referring to Check the long term flood risk for an area in England (https://www.gov.uk/check-long-term-flood-risk). You may be able to get other information on flood risk, by contacting the:
- LLFA
- LPA for information from its SFRA
- water and sewerage company
- internal drainage board if you are in an internal drainage district (https://www.ada.org.uk/idb-map/)
Contact the Environment Agency

If you would like more detailed, site-specific advice on flood risk, such as a review of your draft FRA, visit How to request Environment Agency advice. (https://www.gov.uk/guidance/developers-get-environmental-advice-on-your-planning-proposals#:~:text=To%20request%20charged%2Dfor%20discretionary,%2Dagency.gov.uk.)