Flood Risk Policy in Royal Borough of Kensington and Chelsea

In July 2024, the Royal Borough of Kensington and Chelsea (RBKC) adopted a new Local Plan which has superseded the previous Local Plan (2019).

Within the 2019 Local Plan, Policy CE2 Flooding was the sole policy that focused on reducing the impacts of flood risk, and the implementation of SuDS across the Borough. Now, within the 2024 Local Plan, the flood risk and SuDS requirements have been split across two policies, into Policy GB11: Flood Risk, and Policy GB12: Sustainable Drainage.

Below, we explore the key differences between the 2019 and 2024 Local Plan flood risk and SuDS requirements, and the impacts this will have on development across the Borough. 

Previously, Policy CE2 stated that the Council will resist “vulnerable development”, including self-contained basement dwellings, in Flood Risk Zone 3 and Critical Drainage Areas – thus it specified only that they would resist certain types of development including self-contained basement dwellings, in these areas. Whereas, Policy GB11 of the 2024 Local Plan states that in addition to the above, no sleeping accommodation will be permitted below ground floor level in Flood Zone 3. For context, the extent of Flood Zone 3 within the Borough is provided below. 

As discussed above, previously flood risk and SuDS were considered under one Policy – CE2. However, GB12 of the 2024 Local Plan sets out the local SuDS requirements separately, with some key differences from CE2. 

Policy CE2 stated that the council required major development to achieve greenfield run-off rates and minor development to achieve a reduction of 50% of existing rates. This 50% reduction of rates was applied to the site as a whole, rather than just the footprint or proposed development area, meaning developers were required to provide runoff attenuation for an entire site boundary even if only providing a small rear extension.

Within GB12, this requirement has been relaxed slightly, with the policy wording now stating “Development proposals must aim to achieve greenfield run-off rates. Householder applications must reduce the rate of runoff from the site in a way that is proportionate to the scale of development and reflects the site constraints.” Therefore the updated Local Plan appears to appreciate that on smaller scale developments and compact sites, significant attenuation may not be possible so this allows for more flexibility with the type of SuDS available for minor developments and removes the need to provide 50% reduction in runoff rates for the whole site. 

However the 2024 Local Plan still reiterates that all development needs to play its part in reducing flood risk to the Borough – “All development, regardless of size, should ensure that there is a net reduction in flows to the combined sewer network” – and thus SuDS should still be considered for all development, albeit appropriate to the scale, nature, and constraints of the proposed development.