Can I build housing on a flood plain?

building housing on a flood plain

A number of high profile flooding incidents have put housing development under the microscope. Daniel Hughes explains why building on a flood plain is still a viable option for developers, providing suitable flood prevention measures can be demonstrated.

One of the enduring images of the floods in December 2015 was of a sign in Lancashire announcing that the completely submerged field in the background had planning permission for 39 dwellings.

It was an image that was shared by thousands of social media users – including Environment Agency chiefs. However, it was later revealed that the Environment Agency (EA) had raised no objections when consulted by council planning officers on proposals to build homes on the site near Whalley.

The urgent need to build new homes – even in the flood plain

On the face of it, this may appear to be an untenable stance for the EA. But the situation must be understood in the context of local authorities coming under increasing pressure to find sites for new build homes.

Since planning rules were relaxed in 2011, local planning authorities do not have to report cases where they go against EA advice.

It is additionally important to keep in mind that many homes in at-risk areas are going up with the EA’s full knowledge and consent because the structures are protected by flood defences. Other residential properties are being built without the EA’s involvement because they are in small developments of 10 units or fewer.

The numbers behind flood plain development

Latest figures show new homes are being built in England’s highest-risk flood areas at nearly twice the rate of housing outside flood plains.

According to a study by the Committee on Climate Change (CCC), housing stock in locations where flooding is likely at least once every 30 years has increased at a rate of 1.2 per cent annually since 2011. In contrast, housing outside flood plains (areas with less than a one-in-1,000-year flood) has increased at a rate of 0.7 per cent a year in the same period.

If current trends continue, as many as 20,000 new homes will be built in areas at relatively higher risk of flooding this year.

Risk of flooding is classified as Flood Zone 1 (low probability flooding events); Flood Zone 2 (medium probability); Flood Zone 3a (high probability) and Flood Zone 3b (the functional floodplain). It is important to point out that we all live in a flood zone – the issue is whether you live in a very low, low, moderate, or high risk area.

Why building in a flood plain remains viable

Building new homes on flood plains is seen as a necessity in some instances and this can make flood plain development a viable commercial option – provided an effective and professional approach to planning is taken.

Key to securing any planning permission in areas at higher risk of flooding is the strategic flood risk assessment, prepared by local planning authorities and other relevant bodies and which often underpins the development plan for the area.

Early engagement with emerging development plan documents, particularly the evidence base which underpins such things as flood risk, is important. For individual planning applications, where housing or other more vulnerable uses are proposed, the sequential assessment is a crucial aspect. The idea is to direct development to sites which are subject to lower flooding risk, and only to permit development within areas at increased risk, where there are no reasonable alternatives.

Applications for development in flood plain areas, where supported by a robust sequential assessment, can often succeed, allowing developers to move forwards with schemes and to then deal with the technicalities of “flood resiliency”.

The logic is that risks of flooding will be reduced by flood defences in river flood plain and tidal flood zones, as well as by flood protection measures included in the design of new buildings. Flood plain buildings must usually be raised above the base flood elevation and an engineering assessment is needed to ascertain that there will be no negative implications for upstream properties. Coupled with flood resilient materials and design techniques, it is often possible to reduce the effects of any residual flooding which may occur.

The importance of effective planning

The key to a successful flood plain development lies in a high quality planning application that comprehensively addresses all aspects of flood risk and in some circumstances a sequential search. Developers looking to build in a flood plain area should have a working knowledge of the planning framework and carry out flood risk compliance assessments to establish that building on the flood plain is permissible.

These assessments, along with other flood protection measures, should also be made available to insurers so that residents can insure their homes. High quality planning for Flood Zone 2 and 3 development is crucial to resolve potential flooding issues.

PWA Planning offers a team of Lancashire planning consultants that specialise in advising landowners and developers on planning and development issues, including developments in areas at risk of flooding. For further advice on building in a flood risk area, call Daniel Hughes on 01772 369669.