Flood Risk
The risk of flooding at the proposed development site is one of the key reasons for applying for a judicial review, following the decision by the Planning Inspectorate in 2025 to allow the development on Ham Marshes to go ahead.
The grounds for the claim for judicial review included the following issues:
- Error of law in effectively applying the Exception Test despite the Sequential Test not having been undertaken. The Inspector found, on the one hand, that a Sequential Test was required and that the Exception Test could only be carried out after the Sequential Test; while on the other hand he effectively applied the Exception Test to determine that neither the Proposed Development nor the failure to carry out a Sequential Test would cause “real world harm”;
- Irrational approach to mitigation measures in that the Inspector decided correctly that paragraph 175 of the 2024 National Planning Policy Framework (“2024 NPPF”) clearly states that “land raising”, with no qualifications as to the purpose of such land raising, should not be used as a means to avoid the Sequential Test, and yet he allowed precisely that result through his approach to the lack of “real world harm” due to the proposed mitigation measures;
- Error of law in interpreting paragraph 11(d) of the 2024 NPPF where flooding risk is in issue, to require a substantive risk or harm in order for there to be a “strong reason” for refusal;
Faversham Town Council, Save Ham Marshes
The Sequential Test steers development to areas with the lowest flood risk. It compares your proposed site with other available sites to show which one has the lowest flood risk. The local planning authority may refuse planning permission if other, lower risk sites are identified.
The Exception Test requires two additional elements to be satisfied (as set out in paragraph 164 of the National Planning Policy Framework) before allowing development to be allocated or permitted in situations where suitable sites at lower risk of flooding are not available following application of the sequential test.
It should be demonstrated that:
- Development that has to be in a flood risk area will provide wider sustainability benefits to the community that outweigh flood risk;
- 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.
Here's the background to the flood risk at the site
Much of the proposed development site on Ham Marsh lies within flood zone 1 (low probability of flooding from rivers or the sea). However, the eastern area and the northern end of the strip along Ham Road are in flood zone 3 (high probability of flooding from rivers or the sea). As mitigation for the risks from flooding, the Flood Risk Assessment [FRA] produced for the developers proposes finished floor levels and access roads at 5.75m AOD [above Ordnance datum, i.e. mean sea level].
An Environment Agency stipulation on the development specifies a minimum of 300mm above the flood level of 5.83m AOD.' Such a mitigation measure will require reprofiling of the site to reach the required level. The Faversham Society have calculated that the approximately 36,000 cubic metres of fill, necessitating 2400 deliveries by four-axled vehicles, would cause disruption to the local road network as well as contributing to pollution, noise and carbon emissions.
The Faversham Society also highlights the risk of diverting surface water flooding from the development onto existing adjacent housing; this would include properties in Springhead Road, Upper Brents and Harvey Close.
A further comment by the Environment Agency, dated 24 August 2023, focussing primarily on contamination of water courses and groundwater, states that it has no objection subject to eight conditions outlined in their letter. These include submission and written approval by the local planning authority of a strategy to address the risks associated with contamination of the site prior to occupation of any of the houses, verification that remediation strategies had been implemented and had been shown to be effective.
Another stipulation is that if further contamination is identified during construction, work must cease until a remediation strategy is approved by the local planning authority. The Environment Agency states that no drainage systems, infiltration of surface water drainage into the ground is permitted other than with written consent from the local planning authority. The developer must also submit and get approval for a foul water drainage strategy.
The comment also notes that the existing landfill permit is still current and that the permit holder must continue to carry out monitoring, management and maintenance of the site. The development must not prevent the permit holder from, for example, continuing to access monitoring points. Any waste disturbed by the reprofiling will continue to be considered waste and will need appropriate authorisation to redeposit it.
More significantly, the attenuation basin as a surface water infiltration area is apparently within the engineered phase of the landfill, i.e., the clay layer used to create the walls and base of the containment area. This could lead to saturation of the waste within the area surrounding the attenuation basin, and potentially reduced infiltration capacity and localised flooding of the ground.
The comment concludes by stating that the ‘site is located within the Ham Marshes frontage, which will see maintenance of the embankments cease in the medium term (2048 onwards). Therefore, suitable flood mitigation for this site should be based on the undefended 1 in 200 year (2115) flood level of 5.83m AOD.’ It therefore stipulates that ‘All finished floor levels within the proposed development at the site must be raised to a minimum of 300mm above the flood level of 5.83m AOD.’ (i.e., a total height of 6.13m)
On 22 January 2024 the Environment Agency, in a letter to Swale Borough Council Planning Department, stated that:
‘We have reviewed the submitted FRA for this application site, and we are satisfied that this has included and considered the latest available flood risk modelling for the area. This means that the assessment takes into account the 1 in 200 year flood level and applies suitable uplift to account for 100 years of climate change impacts. We accept that this is appropriate for the application of the Exception test where this is required.
We have therefore advised of suitable finished floor levels for the proposed development, which the LPA has confirmed the applicant has agreed to in an email dated 21 August 2023. This will ensure appropriate mitigation based on the above flood level and climate change considerations.’
On 5 February 2024 the Faversham Society wrote to the Swale Borough Council Planning Department to highlight that the Environment Agency has acknowledged that the applicant’s flood risk assessment is flawed in that it does not conform to policy where it dictates abandonment of existing defences which protect the reclaimed land in the flood plain. Nonetheless, the EA have not directed the applicant to assess the impact of the deflection of floodwaters, which will inevitably occur because of raising the ground level. Therefore, the Society believes that the applicant should submit an addendum to their flood risk assessment that models both the undefended scenario and the impact of flood water constriction and deflection to understand how this will affect residential and industrial properties adjoining the site.
The Faverham Neighbourhood Plan (p.43) notes that community engagement during the development of the plan revealed that flooding and capacity for dealing with flooding are of significant concern. It also comments that reported levels of flooding differ from current mapping data.
