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Flood Risk Sequential Test and Exception Test

Published: 2020-01-27 Updated: 2020-11-05 Subject: Planning, Planning checklist

Planning application - local requirement

When the requirement applies

A Flood Risk Sequential Test compares the site you’re proposing to develop with other available sites, to find out which has the lowest flood risk. The aim is to steer development to the areas with the lowest risk of flooding. 

These tests will also apply to some developments which have to submit a Flood Risk Assessment.

Warning We may have done a sequential test on the site you plan to develop in preparing the Local Plan for our area. Please consult this plan, as you will not need to repeat the test if it has already been done.

Sequential tests

You need to do a sequential test if all of the following apply:

  • There hasn't already been a sequential test for a development of the type you plan to carry out on your proposed site 
  • Your development is in flood zone 2 or 3  
  • Your development goes beyond the scope of a 'minor development'
Minor developments that will not require a test
  • Minor non-residential extensions: this covers industrial, commercial and leisure extensions with a footprint of less than 250 square metres
  • Alterations which do not increase the size of buildings, such as alterations to external appearance
  • Householder development, such as sheds, garages or games rooms within the curtilage of the existing dwelling (but NOT development which creates a new dwelling, such as the conversion of a house to flats)

Exception tests

If your sequential test shows that it isn’t possible to use an alternative site with a lower risk of flooding, you will need to proceed to the Exception Test for certain developments. This will depend on the flood zone the development is located in, and the type of development, as follows:

  • Highly vulnerable development in flood zone 2
  • Essential infrastructure in flood zone 3a or 3b
  • More vulnerable development in flood zone 3a

What the tests should include

The Sequential Test should compare sites in the following ways:

  • Details of the size, location and nature of your proposed development
  • Current use, and proposed future use, of the site
  • Environment Agency flood zone designation for the site 
  • Sources of flood risk on the site
  • Ways that you could avoid or lessen flood risk
  • The likely impact of climate change on flooding risk during the expected lifetime of the development
  • An assessment of the impact of the development on flood risk elsewhere in the area

The GOV.UK website has full details of how to prepare a Sequential Test.

An Exception Test must demonstrate how you’ll manage flood risk on your proposed site. It must also show how the sustainability benefits of the development to the community outweigh the flood risk. The Test must show how the development will be safe for its lifetime, taking into account the vulnerability of its users, and that it won’t increase flood risk elsewhere. 

For a full description of the legal requirements, see the documents below.


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