What are the Sequential and Exception Tests?

The sequential and exception tests are part of the national planning policy that help to ensure that development takes place in appropriate locations and in places of the lowest risk. They allow planners and decision makers to objectively compare different sites and different development applications in order to steer development towards the lowest flood risk areas.


What is the Sequential Test?

The sequential test compares the site you’re proposing to develop with other available sites to find out which has the lowest flood risk.

If you need to carry out a sequential test you can present it in any format as long as you meet the requirements in this guide.

Do I need to apply the sequential test to my development?

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

  • Traditionally if your development is in flood zone 2 or 3

  • a sequential test hasn’t already been done for a development of the type you plan to carry out on your proposed site (you can check this with the local planning authority

  • Guidance as of 20th July 2021, now states that the aim of the sequential test is to steer new development to areas with the lowest risk of flooding from any source.


What types of development don’t need the sequential test?

You don’t need to do a sequential test if one has already been carried out for a development of the type you’re planning (eg a residential development) for your site. In this case, you need to ask your local planning authority for the site allocation reference in their local plan and include it in your planning application.

You also don’t need to do a sequential test if either of the following apply:

  • your development is a minor development

  • your development involves a change of use (eg from commercial to residential) unless your development is a caravan, camping chalet, mobile home or park home site

The NPPF as of 20th July 2021, updated that all plans should apply a sequential risk approach to the location of development – taking into account all sources of flood risk and current and future impacts of climate – as to avoid, where possible, flood risk to people and property.

How can Aegaea help apply the sequential test?

Aegaea’s experts understand the local and national policy and how to apply it. We can access, review and update regional flood modelling to review site flood risk and look at competing sites if information is available, all the way through to building a bespoke flood model to help with the application of the sequential and exception tests We can review and respond to the SFRA and any potential issues that are found.

What is the Exception Test?

The exception test is applied after the sequential test. It is exactly what it sounds like – an exception to the rules of sequential testing. Basically, if there is nowhere else for your development to go, or there are sufficient reasons to make an exception, your development could still take place.

Paragraph 163 of the NPPF states that:

If it is not possible for development to be located in areas with a lower risk of flooding (taking into account wider sustainable development objectives), the exception test may have to be applied. The need for the exception test will depend on the potential vulnerability of the site and of the development proposed, in line with the Flood Risk Vulnerability Classification set out in Annex 3.

How do I apply the Exception Test?

The application of the exception test should be informed by a strategic or site-specific flood risk assessment, depending on whether it is being applied during plan production or at the application stage.

To pass the exception test it should be demonstrated that:

(a) the development would provide wider sustainability benefits to the community that outweigh the flood risk; and

(b) 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.

Aegaea take a long term and sustainable view to the exception test. We promote the ability of a site to reduce flood risk to both the site and to the local area for the lifetime of the development. This is a favourable stance with most planning authorities and demonstrates good will from the developers which in turn promotes more chance of success for the application.

This also fits with the wider sustainability effects of the development as Aegaea can work with you to promote effective SuDS and drainage, watercourse naturalisation and culvert removal, all of which enhance your application.

It is worth noting that to prove betterment and no detrimental effects flood modelling is often required – this process can be time consuming, so it is always worth engaging early as soon as you know that you are in flood zone 2 or 3.

The exception test and the risk based approach to development also means that site master plans and development plans should be done in such a way that the most vulnerable classifications of development should be in the lowest risk areas of the site. Practically speaking, that means that low vulnerability uses such as shops or car parks should be placed in higher risk areas than living accommodation. Guidance from the NPPF states that:

a) within the site, the most vulnerable development is located in areas of lowest flood risk, unless there are overriding reasons to prefer a different location;

b) the development is appropriately flood resistant and resilient such that, in the event of a flood, it could be quickly brought back into use without significant refurbishment;

c) it incorporates sustainable drainage systems, unless there is clear evidence that this would be inappropriate;

d) any residual risk can be safely managed; and

e) safe access and escape routes are included where appropriate, as part of an agreed emergency plan.

How Can Aegaea Help with the Exception test?

Aegaea are able to support the creation of site specific flood risk assessments, including flood modelling and drainage that are compliant with the exception testing principles. We also advise throughout the planning process to our clients to ensure that their development is in line with these policies.

If you have a site that is within flood zone 2 or 3, it is worth checking with Aegaea to understand if you can take the guiding principles of vulnerability and risk into account early in the application procedure to ensure that when it comes to the submission stage, there are no surprises!

Aegaea can provide all the guidance, advice, modelling and information and information that you require to promote flood safe construction, property flood resilience, flood evacuation and management planning and ensuring that residual risks can be safely mitigated.

Each project is unique and as such a bespoke Flood Risk Assessment is required to be more acceptable at planning and should include an Exception Test and Sequential Test.

We are here to help you produce a functioning, viable development which is safe for occupation and responsibly acknowledges the risk of flooding onsite. You can visit our Flood Risk Assessment page, to find out more about that they are, or you can contact us to discuss further on how we can help you. Or if you know what you need a require a Quotation… get a quote.

Request your free, expert quote now

Aegaea work alongside home owners, private developers, planning consultants, architects, local authorities, international development agencies and contractors. Aegaea know exactly how to help you.

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