ACCON UK Limited (ACCON) was commissioned by W. M.
Graham Associates to carry out a flood risk assessment for
the proposed extension of an existing residential property
in Eton Wick, Berkshire. The proposed extension involved
the demolition of the current freestanding garage and coal
bunker and constructing a two-storey extension to the east
of the property in their place.
After contacting the Environment Agency it was established
that the site is located within ‘Flood Zone 3’, which is an
area which has a 1 in 100 chance of being flooded by a river
each year.
The flood risk assessment was carried out in accord in
accordance with the detailed guidance set out in the now
revoked Planning Policy Statement 25 (PPS25)
‘Development and Flood Risk’ and also in line with the
Technical Guidance to the National Planning Policy
Framework (March, 2012).
Within Flood Zone 3, generally “more vulnerable”
developments such as residential are discouraged,
however, due to this being an extension to an existing
property, the Sequential Test and Exception Test are
somewhat redundant, as moving the proposed extension is
not an option. However, similar development proposals for
extensions to other properties in the street have previously
been granted.
As part of this assessment a “Householder and other minor
extensions in Flood Zones 2 and 3, Version 3.1, April 2012”
form was included. The guidance applies to domestic
extensions and non-domestic extensions where the
additional footprint created by the development does not
exceed 250 sq. metres. This form provides options of
mitigation which is required to be included as part of the
development. The options for the development were:
• Floor levels within the proposed development will be set no
lower than existing levels AND, flood proofing of the
proposed development has been incorporated where
appropriate; OR
• Floor levels within the extension will be set 300mm above
the known or modelled 1 in 100 annual probability river
flood (1%) or 1 in 200 annual probability sea flood (0.5%) in
any year. This flood level is the extent of the Flood Zones.
For this development the first option was recommended.
Visit the ACCON UK Ltd website for more information on Bell Lane, Eton Wick - Flood Risk Assessment