Expert view: Pragmatic approach to flood risk key to planning success

2 July 2024

Extreme weather events and severe flooding are now on the rise as the impacts of the climate emergency become more prevalent. As a consequence, this has led to increasing scrutiny of development suitability throughout the planning process in a bid to minimise risks and reduce the catastrophic effects of flooding.

To learn more about why planning authorities are now placing greater emphasis on the Sequential Test as they look to determine site suitability and discover what this means for your upcoming schemes, we caught up with our flood risk expert, Stephen Henry.

‘That’s why we shouldn’t be developing in the floodplain!’ It is an often-repeated statement when we see flooded properties in the news or in our local towns. But how often do we heed our own advice? We are seeing more developments being pushed into inappropriate areas, despite being the specific reason why the sequential risk-based approach was originally incorporated within PPS25, before later being included in the adoption of the NPPF in 2012. Why then, if it has been around for so long, is it suddenly becoming such a key focus for developments?

The sequential risk-based approach states that development should be located in areas of lowest flood risk where appropriate and available. Prior to July 2021, this only applied to flood risk from rivers. The 2021 update to the NPPF stated that the sequential approach should now apply to all sources of flooding, thereby bringing surface water, groundwater, sewers and artificial sources into the equation when determining sequentially preferrable sites. This change, along with greater focus on the increasing flood risk expected with the climate emergency, has resulted in far greater emphasis being placed upon a methodical approach and therefore the need for Sequential Testing.

For developments proposed within areas of higher flood risk, the onus is on the developer to demonstrate that other sites with a lower risk of flooding are not available or appropriate for development. Often, a formal Sequential Test document is used to demonstrate this and is required to support planning applications in a flood risk area.

A Sequential Test is required for all unallocated developments (which are not covered by a Local Planning Authority’s Sequential Test) in Flood Zones 2 or 3, for those at risk of flooding from other sources, or where one hasn’t already been carried out for the development in question. However, a Sequential Test is not required for minor developments or a change of use, except in certain cases such as caravan parks. We would always recommend early engagement with the Local Planning Authority if it is unclear whether a Sequential Test is required, since this approach can avoid unexpected challenges in the later stages of your planning submission.

Once it is determined that a Sequential Test is required, there are some key considerations which demonstrate that, despite the flood risk to the site, there are no sequentially preferable sites available for development. As the onus is on the developer to demonstrate the relative pros and cons of the site, there is flexibility to structure your argument in a way that suits your development:

• Be specific on land use. The more specific you are, the clearer you can be on why developments of this nature are needed in this area. For example, rather than stating ‘educational use’, explain that it is a specific educational use, a nursery for example, and clearly state why it must be available in this location.

• Compare sites of similar size and nature. If your site will be utilised for 100 detached houses, the Sequential Test should compare similar development types and not, for example, a 1,500 home mixed use schemes or 100 flats arranged in blocks.

• Consider flood risk from all sources not only for your site, but for other similar sites. There may be areas of your site within Flood Zone 3, but the development itself is contained within Flood Zones 1 and 2, whereas other sites may have development located within Flood Zone 3, or within higher surface water flood risk zones.

• Consider not only similar developments and sites, but also their availability and deliverability. There may be sequentially preferable sites that have stalled in the planning process due to other technical constraints, which can be used to strengthen your application.

• Consider the catchment of comparable sites. Casting a net too wide brings the potential for more preferable sites, however the LPA will expect a relevant and applicable pool to be considered.

• Consider interdependencies with other land uses. This strengthens the argument supporting why your development should be located on your proposed site.

Once all the above have been considered, it may be the case that there are multiple sequentially preferable and deliverable sites. At this point, it is important to consider the local housing need. If the preferential sites alone do not meet the housing need for the Authority Area, there may still be a need, and therefore a strong case, that your site is appropriate for planning permission.

Want to find out how to apply this to your upcoming development sites, or learn more about the wide-ranging support our flood risk specialists can provide for your next scheme? Contact Stephen Henry in our London flood team.