Rejected Sussex planning appeal demonstrates need for assessing all flood sources


Groundwater flooding is possibly the most underestimated flood source despite the long term damage it can impose upon properties, communities and the environment.

Overlooking this risk in the planning process can be detrimental to a development’s progression; applications have been refused on the basis that groundwater flood risks were not taken into account. 

Last year, Rother District Council rejected a planning appeal for a Sussex residential project due to the lack of “substantive evidence” to illustrate that groundwater flooding would not impact the specified site. 

It is imperative that all sources of flooding are assessed in a planning application, even if the site is overtly at risk from a specific flood source. 

Sussex planning appeal refused

There are four main sources of flooding which need to be accounted for in any planning application; rivers, the sea, rainfall and groundwater. 

The planning practice guidance also identifies overwhelmed sewers and drainage systems, reservoirs, canals and lakes and other artificial sources as additional flood sources. 

Considering these risks is particularly important in light of growing development, outdated drainage systems and intensified weather patterns driven by climate change, all of which increase the chances of flooding. 

In its decision on the appeal for the construction of a residential project in the coastal village of Fairlight in East Sussex, Rother District Council cited the appellant’s failure to regard all flood sources when applying the sequential approach to the development’s location as one reason for its dismissal of the appeal. 

The Council further highlighted how the appellant’s flood risk assessment had revealed the site to be “situated on loamy and clayey soils with naturally high groundwater” and identified that 50 percent of the site was at risk from groundwater flooding. 

Given the National Planning Policy Framework (NPPF) revision in 2021, which now stipulates that all plans should take “into account all sources of flood risk”, the Council declared they could not accept the appeal due to its submission after the NPPF update. 

The appeal’s disregard for groundwater flood risk when a threat was made evident, was considered by the Council as “a matter of sufficient force” which outweighed the development’s benefits alone.  

Guidelines on flood sources 

Since 2018, the NPPF has advised that sequential tests should consider all sources of flood risk. 

Following the 2021 update, paragraph 161 of the framework explicitly stipulates that all sequential, risk-based approaches should take into account all flood risks alongside current and future impacts of climate change. This is to reduce or avoid flood risks affecting people and properties. 

According to the 55th footnote of the NPPF, a site-specific flood risk assessment should be provided for all planning applications for developments which are susceptible to additional sources of flooding. 

Revised to align with the guidelines provided by the NPPF, the flood risk and coastal change section of the planning practice guidance reiterates the need for sequential tests to take all flood sources and climate change into account. 

The guidance states that doing this is the “most effective way of addressing flood risk because it places the least reliance on measures like flood defences, flood warnings and property level resilience features”. 

The guidelines also stipulate that strategic flood risk assessments should exhibit all present and future flood sources as well as identifying sources of uncertainty and how these will be accounted for in a mitigation strategy. 

Further advice is given to professionals to consult alternative bodies involved in flood risk management, especially in cases where a location is vulnerable to other sources of flooding. 

GeoSmart’s groundwater flood risk assessment and sequential test

Alongside the regular flood risk assessments, GeoSmart is also able to provide clients with a groundwater flood risk assessment

Aimed at developers, architects and land surveyors, groundwater flood risk assessments will analyse the risk and impact of this specific flood source on a development site and demonstrate how risks could affect local areas. 

If a groundwater flood risk is realised, the report can provide solutions to support a mitigation strategy and ensure damages are kept to a minimum or avoided entirely. 

GeoSmart can also offer professionals a sequential test to determine available sites with the lowest possible flood risk. 

This test will be undertaken by one of our environmental consultants and an external planning consultant and will usually take six weeks to be completed. 

As shown by the refused appeal for the Sussex residential project, having a sequential test carried out is a vital element of the planning process. 

Contact our team today to find out more about one or both of these reports.