Appeal 3359468

The appeal is dismissed.

The address on the application form and the appeal form, [site address] [site address] , is incorrect. The correct address is as it appears on the Council’s decision letter, 5A, [address], [site address] , Longford, Hillingdon, [postcode] . I have used this address in the heading to this decision above.

I consider that the main issue in this case is whether it is in accordance with policies which seek to provide protection against the risks of flooding.

[address] is a small one bedroom two storey house located at the end of [site address] in a backwater loop of the [name]. The site is in [name] 3. There is mixed development consisting mainly of two storey detached houses on either side of the narrow road along the length of [site address] . The road opens out into a wide area of tarmac in the vicinity of the appeal site which is set back through a gap between two pairs of semi-detached houses.

The relevant policies in this case include SI 12 of the London Plan 2021, EM6 of the Hillingdon Local Plan Part 1 and DMEI 8 and DMEI 9 of the Local Plan Part 2 (November 2012) (the local plan). These all relate to development near watercourses and the management of flood risk, including the potential impact of climate change on flood levels. The National Planning Policy Framework 2024 (the NPPF) addresses the need to plan for managing flood risk and adapting to climate change.

The existing house is close to the river as it loops round to the north and east, and the proposed extension would increase the footprint of the house bringing it closer to the riverbank at the northeast of the site. The appellant has submitted a FRA with the appeal (dated January 2025) correcting the statement in the earlier FRA (dated August 2024) on which the Council based its reason for refusing the application. This states that the footprint of the proposed extension would lie within [name] 3A (land with a high probability of flooding) rather than [name] 3B (functional floodplain, where water has to flow or be stored in times of flood). The appellant also argues that there would be sufficient space between the proposed extension and the river to allow for maintenance and emergency access. He also states that there is an area within the site where the ground level could be excavated and lowered such that the development would not increase flood risk elsewhere.

I consider that this modest extension would be acceptable insofar as it would have no adverse impact on either the character and appearance of the area or on the living conditions of neighbouring residents.

The appellant has suggested that the objection to the proposal on the grounds of the potential risk of flooding and restricted access to the riverbank could be overcome by the imposition of a suitable condition setting out mitigation measures. On the basis of the information before me it seems to me that the proposal, which falls into the definition of minor development in this context, could be acceptable.

However, I am not wholly convinced that there is sufficient detail in either the appellant’s statement or the 2025 FRA to allow me to impose a satisfactory condition which would meet the tests, particularly in terms of precision and enforcement. More detail is required as to the precise amount and parts of the site which fall within [name] 3A and 3B and which area would be available for lowering the ground level to provide mitigation, if necessary. It is also unclear to me where the 8m access for machinery required for maintenance is at present and whether this, or a narrower area could be made available as an acceptable part of the proposal. These matters would be more appropriately dealt with by means of full consultation with the Environment Agency.

In the absence of detailed information regarding suitable measures, I conclude that, although it may be possible to mitigate the flood risk, the appellant has not demonstrated that the proposal would not increase flood risk, contrary to local plan policies EM6, DME1 8 and DMEI9, London Plan policy SI 12 and the NPPF.

For the reasons given above, the appeal is dismissed.