About the project

Ambiental were appointed by their client to support with providing a National Planning Policy Framework (NPPF) compliant Flood Risk Assessments for a side and rear extension to a residential dwelling in Warwickshire to provide greater habitable space.

The site is located in Flood Zones 1 and 3, with the closest watercourse to the site located approximately 11m east of the proposed extension at its closest proximity. This watercourse, Tanyard Stream, is classified by the Environment Agency as a ‘Main River’.

The existing dwelling is a bungalow and therefore the sleeping accommodation is located at ground floor level. The proposed development is for a side and rear single storey extension and can subsequently be defined as Minor Development. The dwelling therefore continues to remain as a bungalow post-development.

Following review from Warwick District Council, planning permission has since been granted approval for the proposed development.

Flood Map for Planning showing the Flood Zones of the site

The Problem 

The site is located partly within Flood Zone 3 and the development could be considered “More Vulnerable” under the NPPF given its residential usage. An EA Main River, Tanyard Stream, is also located within 11m of the proposed extension at its closest proximity. Furthermore, the site is a bungalow and therefore features bedrooms at ground floor level.

Given that the proposed development is for residential use, it is necessary to demonstrate that the proposed development will be safe for its lifetime (100 years, whilst accounting for the impacts of climate change).

The Solution

With reference to the Flood Risk and Coastal Change Planning Practice Guidance, a Minor Development is classified as either:

• A minor non-residential extension: industrial/commercial/leisure etc, extensions shown to create a footprint of less than 250m²;
• Alterations: developments that do not increase the size of buildings e.g. alterations to external appearance; or
• Householder developments: for example, sheds, garages, games rooms etc within the curtilage of the existing dwelling, in addition to physical extensions to the existing dwelling itself. This definition excludes any proposed development that would create a separate dwelling within the curtilage of the existing dwelling e.g. subdivision of houses into flats.

The proposed works is for a household development to provide greater habitable space to the existing dwelling and can be considered a Minor Development. Subsequently, Ambiental were able to recommend mitigation measures in accordance with the Environment Agency’s Standing Advice for Minor Extensions.

With further reference to the Flood Risk and Coastal Change Planning Practice Guidance, Ambiental were also able to argue that Minor Developments, such as the proposed, are unlikely to raise significant flood risk issues.

The Outcome

Ambiental were able to produce a Flood Risk Assessment that argues the proposed development could be considered a Minor Development and that Finished Floor Levels could therefore be set at the existing ground floor level.

Following submission of the FRA, Warwick District Council have since granted approval for the proposed development.