Although we are in the midst of summer the risks of winter flooding remain critical – Norman Hayden looks at the strategies and solutions currently being implemented
On a wild night in late January 2014, families on the flood-inundated Somerset Levels began to be evacuated from their homes. The widespread media coverage of the resulting devastation and hardship helped to make this a pivotal moment in Britain that winter. Storms over a four month period brought torrential rain that wreaked havoc with property through- out the country.
The effect of the 2013-14 floods was significant: around 2,000 properties were hit and clean-up costs alone were £1bn – including repair costs ranging from £30,000 to £100,000 per dwelling – with insurers paying out over £1.5bn. The overall cost to the UK was an estimated £3bn.
The problem is predicted to be a recurring one with climate change likely to cause further major floods in the future. Since 2007, the Government has made considerable investment in defences, which have been very reliant on heavy engineering, tidal barriers and river- side and coastal protection, but even those were to be breached.
The building industry, planners and politicians realise urgent action is needed to deal with the threat long term by protecting and adapting older properties while designing new homes for long-life durability.
Addressing the flood factors
According to the Building Research Establishment (BRE), some 5.2 million homes – nearly one in six properties – are still at risk from surface, river and coastal flooding. Some estimates see the cost of flood damage in the UK rising fivefold by 2050, to £23bn a year.
What factors fuel the problem? Firstly, there’s the design and age of our housing stock. Many homes date back to the Victorian era or are far older, and are not flood-resistant, having been built with permeable materials like timber, lime mortars and plasters and soft bricks.
Secondly, homes have increasingly been built on floodplains – particularly since the 1960s and 70s. Quite naturally, where concrete and asphalt has replaced grass and vegetation, water gets directed into surface drainage systems, often overloading them and causing floods.
Official warnings about the consequences have not been heeded and there are growing calls for a blanket ban on building in flood- prone areas. Despite this, and the fact that councils have to consult the Environment Agency on significant planning applications in districts at risk, around 200,000 homes have been built close to rivers between 2001 and 2011 and this continues today as part of efforts to meet Britain’s housing crisis.
Another reason why floods continue to be a significant problem in the UK is the low uptake of alternative drainage solutions. In 2015, surface water drainage strategies were introduced. Sustainable drainage systems (SuDS) are required to be considered for new buildings or projects that increase a site’s built footprint. This covers any development of over 10 units in Flood Zones
2 and 3, or within an area identified as having a surface water flooding problem.
The idea is to do away with pipes by trying to reproduce natural systems with dirty and surface water drained off through collection, storage and cleaning and then released slowly into watercourses. SuDS strategies comply with national and local planning policies in England, Wales, Scotland and Northern Ireland as well as with the relevant Environmental Agency guidance. However, they are not being fully enforced.
Uncertainty over long-term performance and costs associated with SuDS’ design, implementation and adoption has been an issue in England and Wales. Water companies have thus been reluctant to take up schemes that suggest a large risk. By contrast, Scotland has seen many schemes implemented since 1993.
Faced with the great challenges posed, Sir Michael Pitt’s official report on the 2007 floods urged better preparation and a more innovative approach to housing design. This has resulted in a refocusing on best practice in design and development and use of new materials to the industry standard BS85500 set in 2015.
The twin challenges of resistance and resilience are being tackled. On resistance, the aim is exclusion and dry-proofing – that is, preventing water getting in. For resilience, wet-proofing is the key – if water gets in, how quickly and effectively can houses recover to normality?
One idea is for new houses in flood risk areas to be jacked up on elevated concrete slab-and-pile foundations, allowing underground water to drain quickly. Another idea is for a second basement, which would temporarily hold the water. In this way, standard houses could literally rise and fall in emergency conditions while appearing at all other times exactly like a static house.
Construction ideas include solid walls with external render along with cavity wall membranes. Products involving doors, windows, special kitchens, water-resistant wall and floor membranes that channel water towards drains and sumps that disperse water quickly are all being explored. For older houses this would obviously mean retrofitting.
Research is also taking place into resilient surfaces such as robust boards, and the positioning of toilet and sink non-return valves, plus the placing of electrics and home appliances above expected water levels, are other items of key interest.
Architect and Construction Products Association deputy chief executive Peter Caplehorn points to the progress being made: “We have a range of materials available in the construction industry which can be used in just about every part of the home to make it resistant to flooding,” he says. “We have floor finishes that can cope with complete immersion in water, wall finishes and plasters that don’t absorb water and doors and windows, which will take a fair amount of flooding.”
Such materials and products have been incorporated in projects such as the recently-launched Building Research Establishment (BRE) Resilient House.
The project, in conjunction with industry partners, is taking place in a building within the BRE’s experimental Victorian Terrace at Watford. This refurbishment – employing simple solutions to stop water getting in, and being more resilient if it does – has the mass housebuilding sector in mind.
Elsewhere, a ‘buoyant homes’ project on an island on the Thames at Marlow, Buckinghamshire has seen the emergence of Britain’s first amphibious house designed by London-based Baca Architects using technology pioneered in the Netherlands.
The site of the three-bedroom family home is in a designated Flood Zone 3b within a conservation area and contains a ‘can-float’ basement, which rises in its dock-like foundations to avoid flood water. Following the completion of construction, the property was successfully test-floated at the beginning of this year.
Baca director Richard Coutts says:
“Marlow’s Amphibious House is a case of technology and design coming together. It is proof that flood-conscious architecture is feasible, we call this Aquatecture. The Marlow House opens a new way of building with water, instead of against it.”
A similar project sees Berfield, a joint venture company owned by the Larkfleet Group and Floodline Developments, looking to build 24 ‘floating’ homes, among a wider development, on the edge of Theale Lake, south of the village of Burghfield, Berkshire. The houses will have three core components – a concrete basin, buoyant basement structure and guide piles – and are designed to float if the lake overflows.
Inevitably, there are questions about resilience. Will older houses function normally with upgrading? Will resilient homes allow a return to normal? Would their features affect the design of a house? Will they prove too expensive and esoteric for volume house building?
The case for resilience is also hampered by the fact that Building Regulations are currently more concerned with flood avoidance. Planning may require restrictions to be placed to ensure resistance or resilience measures, but these are not always followed through into the construction.
This has resulted in a very uncertain market for flood-resilient property even with new-build guarantees such as the BRE’s Home Quality Mark.
The CPA’s Peter Caplehorn looks at it this way:
“When you get on to things like insulation which people want for comfort and efficiency, it gets complicated because a home that is completely resilient to water begins to look like a prison.”
He feels mandatory regulations would help bring about a more robust approach. “We need to look at Building Regulations covering flood resilience because, between developers and local authorities, nobody wants to take on the investment, bite the bullet and get on with it.’’
Far greater investment is clearly needed. RIBA puts the UK’s under-spend on flooding at £580m and urges the Government to adopt a joined-up approach to development in high-risk areas by looking beyond just ‘building now and protecting later.’
The cost to homeowners needs to be considered. Even if greater protection of homes added to property values, would homeowners in risk areas end up paying overall through expensive repair/insurance premiums? Traditionally, ‘no betterment’ clauses have prevented insurers from assisting in the finance of flood protection. Occasionally, insurers stipulate that homeowners must adopt measures and, in some cases, will not insure if the repairs to a property are not resilient.
From 2015 the Government-backed Flood Re scheme, run and funded by insurers, covers those in high-risk homes who might other- wise struggle to get affordable insurance. The worry is that the pressure for new housing might lead to further flood-prone homes which would outstrip the ability of even Flood Re to insure them.
Uncertainties abound. But what seems clear, is that unless bold ideas on flood resistance and resilience are taken up there will be many more distressing scenes like those seen on the Somerset Levels a few winters ago.