Why new build houses are a flood risk to existing homes
People’s homes will be at greater risk from flooding by 2020 because new homes will overwhelm existing drains, according to the biggest ever survey of building and flooding professionals. More sustainable drainage systems is the answer.
People’s homes will be at greater risk from flooding by 2020 because new homes will overwhelm existing drains, according to the biggest ever survey of relevant building and flooding professionals.
The Government is planning to build a million more new homes by the end of the decade. But the survey suggests current planning laws in England will make it too easy to automatically connect new homes to already over-capacity mains drainage, rather than look at sustainable options like soakaways which can be cheaper and simpler and avoid adding to flood risk.
Overwhelmed drains are the most common type of flooding in towns, costing the economy £260m per year. Greater London is an example where urban development connecting to drains has added to the flood risk for homes generally. In the 2007 floods nearly all the 1,400 properties flooded were due to surface water flooding.
The survey of 539 industry professionals including engineering consultants, flood advisors and planners shows:
- 70% think current planning policies don’t sufficiently encourage sustainable options instead;
- 65% think the Government’s non-statutory standards for sustainable options aren’t effective anyway;
- 75% think local authorities don’t have the in-house expertise to check and advise on sustainable options or challenge proposals that might increase flood risk.
The survey was conducted by organisations including the Wildfowl & Wetlands Trust (WWT) and the Chartered Institution of Water and Environmental Management (CIWEM). They are now urging the Government to strengthen planning law in England so that:
- All new developments would use sustainable drainage systems (known as SuDS) where possible, which are often cheaper and simpler;
- Better standards would be drawn up to help developers to build good SuDS that also improve water quality and biodiversity, and to be clear on who will adopt responsibility once built;
- The Government would then review the impacts on communities beyond each development itself, with a view to extending SuDS to older buildings in order to reduce this most common type of flood risk in cheap, simple ways that don’t require big expensive projects.
WWT Chief Executive Martin Spray said:
“The Government’s freeze on sustainable drainage policy is a loss for wildlife and a loss for communities. It is time for clarity: developers must include good natural drainage systems for our homes, and Government must make sure they are maintained. We can make this change affordable and quickly, delivering new defences and new habitats, without slowing down house-building.”
CIWEM Chief Executive Terry Fuller said:
“We recognise the urgent need for one million new homes but it is pointless to build in a way that creates flood risk for the future. Our analysis shows that the main obstacles to high-quality and widely implemented SuDS are political and institutional rather than technical or financial so there is no reason why Government should not support stronger policy to deliver sustainable drainage widely.”
What are sustainable drainage systems?
Sustainable Drainage Systems (SuDS) mimic natural processes. SuDS features might include soakaways, ponds, or bog gardens that all aim to temporarily store stormwater and release it slowly. This stops it rushing off hard surfaces like tarmac and tiles and overwhelming drains or local watercourses. At the same time, these SuDS filter the water so it is cleaner when it finally reaches a drain or river. Surface SuDS like wetlands can also be great for wildlife and also make homes an attractive place to live.
Following widespread UK flooding in 2007 which cost £3.2bn, Parliament passed a law requiring all new developers to exhaust SuDS options before connecting to a mains. But the Government has never implemented it for the majority of new developments. The CIWEM/WWT survey found that even where developers do consider SuDS, the main barriers are perceived cost, on-site constraints and concern for who will pay for any onward maintenance – but that these barriers are often unjustified. Government research shows SuDS are often cheaper to build and maintain.
After seven years of non-action, the Housing and Planning Act 2016 includes a requirement for the Government to review whether current SuDS provisions are working in England. This survey will be submitted to that review.
Scotland, Northern Ireland and Wales have all made greater progress than England regarding policy to promote sustainable drainage. In Scotland SuDS are now a general requirement; in Northern Ireland an Act which ends the automatic right to connect to drains was passed in 2016; and Wales has extensive standards for sustainable drainage.
SuDS designed by WWT include this one at a school in North London, which shows how simple SuDS can be. Water from the roof flows down the drainpipe into a bog garden and pond, while water from the car park is channelled across a grass strip into a gravel swale (video courtesy of project partners the Environment Agency):
Alongside WWT and CIWEM, the survey and report is supported by: Royal Town Planning Institute (RTPI), Royal Institute of British Architects (RIBA), Institution of Civil Engineers (ICE), Institution of Environmental Sciences (IES), Landscape Institute, University of Exeter Centre for Water Systems, Susdrain, Association of Drainage Authorities (ADA), the Construction Industry Council Champion for Flood Mitigation and Resilience, RSPB, WWF, the Angling Trust, Buglife, Salmon and Trout Conservation UK; Cornwall Community Flood Forum and Future Water Association.
