Building homes on a floodplain

Of the various disasters which can befall a home owner, flooding must be right up there as one of the most traumatic.  No respecter of property or people, it can rob people of treasured possessions and turn their lives upside-down.

So you have to feel for those who have seen their homes inundated this winter, whether here in Norfolk, or elsewhere in the UK.

Inevitably when these things happen, people try to seek an explanation, and one of the most common refrains is that house builders are to blame, for not taking enough care to ensure they don’t build homes which are susceptible to flooding.

In fact, nothing could be further from the truth.  We house builders face stringent rules about what we must do to ensure our developments do not increase the risk of flooding. 

Nowadays we have to design our sites so that even if a ‘once in 100 year’ storm happens, there will be no effect to the risk of flooding (and there is an extra margin of error built in for climate change).

We have to ensure that all surface water is either allowed to leach naturally back into the ground (as it would on an open field), or else be held through what is called ‘attenuation’ (essentially on-site storage) and then released back via flow chambers into the water courses or sewer, at the rate that it would have done had the land not been developed.

Furthermore, developments have to be designed so that surface water is released in a controlled manner to prevent downstream flooding.  Not only are we preventing our own sites from flooding, but we are also ensuring that they do not impact on other locations.

These measures are complicated and have an impact on design and construction costs.  As well as using ‘Sustainable Urban Drainage’ techniques, the design of the house itself may have to change.  For example, there may be possible increases in foundation costs to ensure stability, through measures such as piling; we might raise ground floor levels to ensure that properties are above predicted water levels; or we might also raise vehicle and pedestrian routes to ensure access.

To sum up, all new developments must be designed in such a way that they do not have a negative effect in terms of flood risk.  This robust regulation is the right way to go when building new homes, but it does add to the cost of the homes themselves.

That, of course, is a price worth paying.  No-one, including house builders, want to see scenes such as those we have witnessed on our TV screens over the past weeks.  But lazily blaming developers when the causes are varied and complex does no-one any favours – particularly when that blame is manifestly misplaced.

• Our friends at consulting engineers Plandescil have helped us put together an overview of how we design drainage systems for new developments.  You can find this at www.ablehomes.co.uk/drainagedesign.