Sequential Test: What do we need to know?

What is a sequential test?

A sequential test is carried out to ensure development is sited on land that has the lowest risk of flooding within the Local Council area. For example, available sites in Flood Zone 1 should be considered above those sites in Flood Zone 2.

When is a sequential test required?

A sequential test is often required when the proposed development site is within Flood Zones 2 or 3.

Are there any exemptions from a sequential test?

Yes, a flood risk sequential test is not required:

  • if the project is a change of use;
  • if the development is located in Flood Zone 1;
  • for some minor developments, e.g. a shed, extension etc.
flooded street

flooded street

What is included in a sequential test report?

Typically, a sequential test report includes:

  • Introduction – location details of the site and the reason for the test, e.g. it falls within Flood Zone 2 or 3;
  • Background – details of any previous planning applications and whether the site falls within the local authority SLAA.
  • Proposal – details the planning objective and general comments about the site.
  • Site Analysis – more detailed content about the location often including a map, information about the current use, hydrological features, flood risk and flood mitigation measures.
  • Local Policy – details of the documentation, plans and policies being utilised by the local authority where the site is situated.
  • Sequential test Approach – details of the criteria used to assess the site.
  • Sequential test Site Specific – this can include a review of the local authority plans in relation to the site, comparisons of sites and a review of available sites on the open market.
  • Conclusion – commentary on the site and explicit confirmation of whether the sequential test has been passed.

What does SLAA stand for?

SLAA is an abbreviation for Strategic Land Availability Assessment. This is a technical document which assesses the suitability, availability and achievability of land for housing and employment development.

Who can carry out a sequential test?

There is no requirement by local authorities for the person who carries out the flood risk sequential test to hold a particular qualification, however you will often find they are carried out by individuals who have significant knowledge in flood risk, such as an environmental consultant.

Does a sequential test require a site visit?

No, there is no requirement to visit the site, as data and information can be obtained remotely.

Can a development proposal fail a sequential test?

A development proposal will only fail to pass the sequential test if alternative sites are identified within the search area that are at lower risk of flooding, appropriate for the proposed development and are ‘reasonably available’ for development. A site is only considered to be reasonably available if it is both ‘deliverable’ and ‘developable’ as defined by the NPPF.

When is a site considered “reasonably available”?

The definition of ‘reasonably available sites’ has been extracted and interpreted from both the National Planning Policy Framework (Footnote 11 and 12) (2018) and “Demonstrating the Flood Risk Sequential Test for Planning Applications” document (2014) prepared by the Environment Agency. This defines reasonably available as sites that are suitable, developable & deliverable.

When is a development considered “deliverable”?

To be considered deliverable, sites should be available now, offer a suitable location for development now, and be achievable with a realistic prospect that housing will be delivered on the site within five years and in particular that development of the site is viable. In accordance with paragraph 47 of the NPPF (2019) sites with planning permission should be considered deliverable until permission expires.  This applies, unless there is clear evidence that schemes will not be implemented within five years, for example they will not be viable, there is no longer a demand for the type of units or sites that have long term phasing plans.

When is a site considered “developable”?

Developable – sites should be in a suitable location for development and there should be a reasonable prospect that the site is available and could be viably developed at the point envisaged.

What happens if there are no alternative sites?

If there are no potential alternative development locations at a lower flood risk than the subject site. Then the site and proposed development is considered to have passed the sequential test, but requires application of the Exception Test.

What is an exception test?

In line with paragraph 102 of the NPPF (2019), if following the application of the sequential test, it is not possible for the development to be located in Flood Zones with a lower probability of flooding, the Exception Test can be applied.

What does the exception test seek to explore?

The exception test consists of two components; demonstrating that flood risk can be managed for the lifetime of the development and consideration of the wider sustainability benefits to the community that outweigh flood risk.

How is an exception test passed?

For the exception test to be passed all of the following criteria must be met:

  1. It must be demonstrated that the development provides wider sustainability benefits to the community that outweigh flood risk, informed by a strategic flood risk assessment where one has been prepared; and
  2. A site-specific flood risk assessment must demonstrate that the development will be safe for its lifetime taking account of the vulnerability of its users, without increasing flood risk elsewhere, and, where possible, will reduce flood risk overall.

For more information on sequential tests or any of our environmental reports, call us on 01743 562262 or email