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What is the Sequential Test?

Image result for uk flooding wikimedia commons


Southwest Environmental Limited can undertake a Sequential Test for your project. Our method meets with 90% acceptance rates when we include the Sequential Test as part of our standard Flood Risk Assessment .

The Sequential Test is one of our least favorite topics upon which to write a report. For the simple reason it is utterly illogical. Of course it is good to move development away from flooding risk areas, but most customers already own the site, so choosing a different one is not really an option!

A Sequential test also has the most variable scope out of any report we write, and so is difficult (but not impossible) to give a fixed price for. It can start out as a few paragraphs in the Flood Risk Assessment, but in some cases it can involve searches of  Estate Agents Listings, Core Strategies, Strategic Housing Land Availability Documents, 10 Years of Past Planning Approvals, and in some instance has to consider Surface Water Flooding as well as more Common Fluvial and Tidal Flooding.

So we don't really enjoy writing these.

Sequential Test Legislation

Planning Policy Statement 25: Development and Flood Risk (PPS25) sets out national planning guidance in relation to flood risk. PPS25 requires Local Planning Authorities (LPAs) to take a sequential risk-based approach to determine the suitability of land for development when allocating sites in the Local Development Framework (LDF) or determining planning applications.

Through the application of the sequential test, the overarching aim of PPS25 is to steer development to areas at low risk from flooding.

 PPS25 articulates a presumption in favor of locating new development in Flood Zone 1 (low probability). If there are no reasonably available sites in Flood Zone 1, the flood vulnerability of the proposed development can be taken into account in locating development in Flood Zone 2 (medium probability) and then Flood Zone 3 (3a high probability and 3b functional floodplain). Image: Andrew Smith / Flooding in Bucklebury, via Wikimedia Commons

The Sequential Test aims to ensure that development does not take place in areas at high risk of flooding when appropriate areas of lower risk are reasonably available.

Paragraph 19 of PPS25 recognizes the fact that wider sustainable development criteria may require the development of some land that cannot be delivered through the sequential test. In these circumstances, the Exception Test can be applied to some developments depending on their vulnerability classification (Table D.2 of PPS25). The Exception Test provides a method of managing flood risk while still allowing necessary development to occur.

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When is the Sequential Test required?

Which County, City or Borough has Good Guidance on the Sequential Test?

How is the Sequential Test Applied?

Sites with Planning as a Reasonable Alternative

Sequential Test Example Projects

How to Carry Out the Sequential Test

Choosing Your Sequential Test Search Area?

Sequential Test Problems

Sequential Test Stops Planning

 When is the Sequential Test required?

Development proposals within flood risk zones 2, 3a and 3b must have gone through a sequential testing process unless any of the following circumstances apply:

1.If the development is considered to be inappropriate for the flood zone of the site. These circumstances are listed in table C below and more fully in table 3 of the NPPF Technical Guidance. In such circumstances permission would normally be refused and therefore it is not advisable to submit a planning application.

2.The proposal is for the change of use of land/buildings only*.

3.The proposal is a minor non-residential extension only (i.e. less than 250 square metres)

4.The proposal is development that does not increase the size of the building e.g. alterations to external appearance.

5.The proposal is for householder development (extensions and detached buildings etc) provided that the proposal is not associated with the creation of a separate unit of residential accommodation.

6.We, as part of the Local Development Framework (LDF) or Local Plan process, have already sequentially tested the site**.

7.For a replacement building (see the PPS25 Practice Guide, para. 4.40)***.

8.For an ongoing and existing regeneration scheme (see the Practice Guide, para. 4.38). Although in such circumstances a sequential approach to the location of development within the application site may still need to be applied.

* Except for any proposal involving a change of use to a caravan, camping or chalet site, or to a  mobile home or park home site, where the Sequential and Exception Tests should be applied as  appropriate. For any change of use, if significant operational development (physical works) is  proposed then evidence of a Sequential Test is required.

**If the proposed development is not in accordance with the allocations and relevant planning  policies then a Sequential Test will need to be submitted with the application. For example, if  housing is proposed on a site allocated for a less vulnerable industrial use.

*** Where an applicant seeks to redevelop a property, by demolishing an existing building and  erecting a new one, the Sequential Test need not be applied so long as the following criteria are satisfied

How to Carry Out the Sequential Test

At a national level guidance on how to carry out the sequential test is very wooly / vague / nebulous. However there is some guide guidance available in some areas at a local level, and where this does occur it is a godsend / blessing / bonus.

Without a good set of rules on how to carry out the sequential test you are left at the mercy of whoever is assessing your sequential test report. That would be you local planning authority (LPA).

The test requires that other sites in the area are checked to see if they are viable alternatives, to the site you are proposing. In reality this is crazy because most of our clients already own the piece of land they are trying to develop, and so to consider alternatives is . . . not realistic.

Thankfully in areas where LPAs have a good set of rules there are a list of criteria, which an alternate site must meet to become a viable alternative. These might include area, planning status, geo-locality and in short this results in most development sites in the area being found to be unsuitable.

If you are looking to undertake this work yourself, it can be done if you have the time. Bristol City Council have the best guidance I know of, perhaps use that if your LPA does not publish its own guidance on sequential testing. However, if you would rather we carry out your sequential test on your behalf then please get in touch.

Please feel free to contact the office for an informal discussion regarding your requirements.

How is the Sequential Test Applied?

The sequential test is applied in very different ways depending on who is dealing with the application. It is left to the "local authority" to choose alternative site search criteria. This introduces a massive amount of subjectivity in to the process. Some planning officers may be very pragmatic in their application of the sequential test, whilst other . . . not so.

The problem on the whole is the complete lack of guidance on how the sequential test should be applied. With the exception of 2 administrative areas that SWEL know of(see below), the NPPF is followed to the letter, which states that the entire administrative area (i.e. district council) should be considered for the alternative site search area. This introduces a number of problems, but first let us consider some of the other assessment criteria which are sometimes used: such as size and proximity to public services.


A small garden infill plot could not be considered as a reasonable alternative to a large multi-residential development.


If you have a single plot valued at 200,000, then a 1,000,000 site is not likely to be considered a reasonable alternative.

Public Services

Distance to public transport hubs might also be considered. If you site is within 100 meters of a bus stop of train station, then this is a positive sustainability feature that you could use to compare it against other perhaps less sustainable options.

Which County, City or Borough has Good Guidance on the Sequential Test?

Many of the assessment criteria (other than search area) stem from the Excellent guide published by Bristol City Council. This is the only solid guidance SWEL know of. Other authorities have defined search areas that break down their administrative area in to smaller sections. The Lake District National Park for example have a set of discrete areas within their boundary such as "north east" and "central".

Any guidance given in writing from your local authority is a bonus since, there is so little guidance around!

Choosing Your Sequential Test Search Area?

In general you will not get to choose. The area is chosen by the planning authority. There is no harm in suggesting a search area, or SWEL preparing your sequential test using our own search area, but you should expect in 25% - 50% of cases that this will be contested.

Example: In a recent report in Salford (Manchester) we were asked to consider a 1km search radius, despite this overlapping in to several wards of Salford. In other cases we might asked to consider a planning authorities enforcement area, such as Westminster City Council.

Regeneration Areas are commonly used as a search area, we have used regeneration areas for reports in South-end-on-Sea and Rochford District Council Areas

Sequential Test at Planning Appeal

We have had 1 appeal case to date that have in centered around the sequential test. In this instance South Gloucestershire Council insisted on the use of a very broad sequential test search criteria which consisted of any alternative land within flood zone 1 in the whole of South Gloucestershire! We considered this to be wholly unreasonable, but to our surprise the appeal inspector supported this view.

This demonstrates the futility of trying to appeal against sequential testing decisions, and also the fact that the local authority have supreme power in determining the outcome of the sequential test.

Sites with Planning as a Reasonable Alternative

North Somerset Council (by Example) will not consider sites with planning granted as reasonably alternative. I would query why sites with planning consent cannot be considered, and as a result any site without planning could therefore be considered. The planning process depends on so many different aspects meshing together for a project to be successful, so by considering a site without planning one is comparing a partially known site, to an unknown one. Even if a site without planning were deliverable with regards to sequential test assessment criteria, then it could be undeliverable when considering any number of any other factors such as transport, drainage, feasibility, noise etc. which would not be apparent at the time of carrying out the test. Bearing these factors in mind, would it not be fair to include a list of criteria for the assessment of alternative sites that make account for these unknowns.

Sequential Test Problems

We perhaps 3 or 4 times year received phone calls from exasperated individuals or company representatives who are have problems passing the sequential test. These normally fall within 2 categories:

1 - Concept Error

Proposed: Trying to build a large industrial build next to a small house, or building a small house next to a large industrial building. Building a house which is too large when compared to surrounding houses. i.e. Trying to get planning for something that is unrealistic.

2 - Personal Differences

Applicant or Landowner has had a "difference of opinion" with planning officer. This could involve lost tempers (farmers usually), strategic crying (ladies usually) or trying to throw the planner's own rule book at them (retired army or naval officers usually).

Either of the above situations may cause the planning officer to play their trump card: The Sequential Test. Outside of Bristol they are rule maker and rule keeper, and that leaves the applicant, and us if involved, in a very sticky place.

So however you are actually feeling about your planning application never loose you temper / cool / respect (pretend if needed) for your planning officer, it is counter productive, and will cost you hard cash.  Don't do it!

Sequential Test Stops Planning

A few "road-blocks" that the planning officer can present are as follows: 

  1. Extend to searching unimplemented planning persimmons. - We can list say 20 examples, but a thorough search is so time consuming as to be impossible. 
  2. Repeat whole exercise considering surface water flood zones. - Again technically possible but very time consuming. 
  3. Very Large Search Area - We would know this before we started but if the search area is very large, this makes it an expensive process. 
  4. Names Site - Planning officer names a site as suitable. 
  5. Parts of Larger Site - Upon identifying a larger site (200 units SHLAA type) the planning officer will suggest using a small part of a larger site as acceptable. 

With the exception of point 3, we can't really predict what will be asked for (sometimes none of the above), and so a full scope Sequential Test (to cover all eventualities) would be cost inhibitive to most, and even then could be scuppered by point 3.

2022 Updates to NPPG

Recent newsletter indicates that: "Greater detail on the purpose and application of both the Sequential Test  and the Exception Test. Including detail on key terms such as “reasonably  available” and “wider sustainable development objectives”.

Comparing new and older versions of the guidance we can see that, some extra detail has been provided on "reasonably alterative" sites, although in reality very little has changed, as most of the detail provided was known to us, and pre-existing in other policy or guidance documents.

Sequential Test Example Projects

Review of Sequential Test for Rochford District Council

Sequential Test for Residential Development in Yorkshire