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Flood risk information

Information about flood risk assessments


Flooding from rivers and coastal waters is a natural process. It plays an important role in shaping the natural environment. But, flooding can cause risk to life and damage to property.

Flood risk is an issue that you need to consider if you're planning any new development, including home extensions and change of use.

Flood risk assessments 

Flood risk assessments are the tool used to assess and manage the flood risk to, and resulting from, different kinds of development.

You'll need to submit a flood risk assessment with the planning application if:

  • the property or site is at risk of flooding; or
  • the development is one hectare or more in size 

For further information see flood risk assessment for planning applications on GOV.UK.

As part of your application you'll need to submit one of the following forms to show you've applied the sequential and exception tests to your site:

Flood risk mapping

To identify whether the site is at flood risk, please look at our Strategic Flood Risk Assessment (SFRA) mapping.

Details of these mapping facilities can be found on our flood risk assessment page.

For more detailed assessments the modelling used to inform the SFRA can be obtained from the Environment Agency.

Flood zones

Development in flood zone one - low flood risk

If the site is at a low direct risk of fluvial or tidal flooding, you'll not need to submit a flood risk assessment with your planning application, unless the site is identified as being at risk from another source of flooding or is one hectare or greater in area.

Development in SFRA flood zone two - medium flood risk

A full flood risk assessment will not be required:

  • for developments of less than one hectare which fall within flood zone two of the SFRA map


  • the site is shown to be at risk due to the impacts of climate change
  • the site is at residual risk of flooding due to the failure or overtopping of the existing defences
  • the site is at risk of flooding from another source of flooding (for example, surface water flooding)

Instead, you'll need to follow the standing advice on the GOV.UK website.

Development in SFRA flood zone three - high flood risk

You'll need to submit a flood risk assessment or follow the standing advice on the GOV.UK website alongside your planning application:

  • for a development which is identified as falling within flood zone three of the SFRA

Flood risk design

We provide some advice on how to reduce the risk of flooding to both the property and future occupants. Please see our flood risk design guidance page.

Sustainable drainage systems (SUDs)

It's important to reduce the causes and impacts of flooding.

Sustainable drainage systems are designed to control surface water run off close to where it falls and mimic natural drainage as closely as possible. 

For further information about sustainable drainage systems and planning considerations, please see the Planning Practice website, or download DEFRA's sustainable drainage systems guidance booklet.

Coastal flood risk between Wolferton Creek and Hunstanton

If you're thinking of submitting a planning application within this coastal area, you should refer to Policy DM18 of the Adopted Local Plan. Planning applications for development within this area must agree with the criteria set out within Policy DM18.

You'll also need to include a Flood Risk Assessment with your planning application if you're renewing existing temporary permissions for:

  • mobile homes
  • park homes
  • caravans

Further information

You can find out more in our technical flood risk information leaflet.