How have planning updates tightened sequential and exception tests guidelines? 



Amendments to the flood risk and coastal change category of the planning practice guidance (PPG) have made obtaining planning permission for developments in medium to high flood risk areas more difficult. 

The update, which was carried out to better align the PPG with the National Planning Policy Framework (NPPF), included changes to the sequential test and exception test guidelines and has increased the likelihood of councils requesting these flood risk tests during the planning application process. 

Reflecting the NPPF, the new guidance places greater emphasis on climate change and the importance of flood risk testing to account for increasing, climate-driven flood events in the UK. 

To help you better understand the changes, GeoSmart Information’s principal hydrologist, Mike Piotrowski explores how the update will affect sequential and exception tests. 


What are sequential and exception tests? 

A sequential test is an analysis carried out to make sure a development is built on land that has the lowest chance of flooding out of the available location options. 

“A sequential test is compulsory for sites in flood zones 2 and 3. However, the revised National Planning Policy Framework and supporting planning practice guidance states these tests are now required for sites affected by surface water and groundwater flooding. This is where there is a medium or high risk of flooding from those sources,” Mike said. 

Paragraph 024 of the PPG states that a sequential test should consider appropriate medium flood risk areas if it has previously found no suitable low risk sites to place a development. 

If no low or medium risk sites are available, a sequential test must identify an appropriate high risk site for the development or reject the proposed building altogether. 

Only after a development passes the initial sequential test can an exception test be conducted.

This test is a two-pronged method to assess how a development will impact flood risks in the immediate and surrounding area. 

To pass an exception test, the updated PPG stipulates that: 

  • A development that has to be in a flood risk area will provide wider sustainability benefits to the community, that outweigh flood risk; and
  • A 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.

According to Paragraph 035 of the PPG, such sustainability benefits could include: 

  • The re-use of suitable brownfield land as part of a local regeneration scheme;
  • An overall reduction in flood risk to the wider community through the provision of, or financial contribution to, flood risk management infrastructure;
  • The provision of multifunctional sustainable drainage systems that integrate with green infrastructure, significantly exceeding National Planning Policy Framework policy requirements for sustainable drainage systems;

According to Mike, other benefits that could exist include the use of local building firms and/or maintenance firms to provide local employment over the development’s lifetime or the improvement of local facilities such as schools or doctor surgeries located within a development. 

Mike added that whilst it is the responsibility of the exception test to determine whether  development would be safe from flood risks for the duration of its lifetime, it was the role of flood risk assessments to demonstrate how these risks are mitigated and managed. 


Who carries out sequential and exception tests? 

The work for sequential tests and exception tests is divided into two parts; half is carried out by one of GeoSmart’s environmental consultants and half by an external planning consultant. 

“Qualitative and quantitative information is presented in both of these tests, the former of which is mostly carried out by the environmental consultant whilst the latter is largely undertaken by the planning consultant,” Mike said. 

In total, it usually takes 30 days for either of the tests to be completed, a process which is divided into thirds: 

  • 10 days for proposed search parameters to be confirmed
  • 10 days for GeoSmart’s environmental consultant to complete the flood risk component of the testing
  • 10 days for the external planning consultant to finalise the planning elements


How are climate change factors accounted for? 

Paragraph 024 of the PPG states that a sequential test should take ‘all sources of flood risk and climate change into account.’ 

In other words, a sequential test needs to identify whether a development site could be vulnerable to future forms of flooding. 

But why does this new guidance increase the chances of councils requesting sequential tests? 

“The sequential test is mostly undertaken for the present day scenario but there have been certain councils trying to stipulate the requirement for a test on the basis of future flood zones they have drawn up in the last couple of years,” said Mike. 

“This approach has now been strengthened by the revised NPPF and PPG and we are likely to see more sequential tests required for more sites, both on the basis that there is now a trigger for them on more flooding sources and the climate change aspect.”


How will climate change affect planning permission? 

On top of increasing the severity and frequency of flooding in the UK, the climate crisis could equally cause current flood zone 1 areas to be relabelled as locations in flood zones 2 or 3. 

“Some local councils are already using the term ‘future flood zones 2 and 3’ to place a requirement on a flood risk assessment or the sequential and exceptions tests including some southern coastal areas in Hampshire and West Sussex,” Mike explained.  

“In England, the Environment Agency (directed by the government policy) holds the power to change the flood zones to include climate change. In Wales, the new flood map for planning, which will be implemented in June 2023, already has climate change built into the extent of flooding.”


Require a sequential test or exception test?

If you would like a sequential test or exception test for your development, please get in touch with our team today