Can we build homes in floodzones?

Image above by Francis Design www.francisdesign.com

Context:

The Ministry of Housing, Communities and Local Government is consulting on the draft text of the National Planning Policy Framework (NPPF). Consultation closes on 10 May 2018. Since the publication of the NPPF in 2012 considerable advances have been made in the development of fully flood proof homes. So it is now sensible to ask:

Can we build homes in flood zones?

3 April 2018

Yes we can and this is why we should:

  • 1. The UK needs to build around 300,000 new homes a year
  • 2. Much of the most desirable land in the UK is located in flood zones
  • 3. The flood land is often within or next to existing villages and towns and not in the Green Belt
  • 4. There is proven technology available to build in flood land sustainably

That’s why government policy should be reviewed so that it takes account of available technology.

What Lord Smith, former Chairman of the Environment Agency, advised in 2014:

He said measures needed to be taken to cope with floods when they hit, including the possible construction of Dutch-style homes which could float above the rising waters. He said it would be ‘impractical’ to impose a blanket ban on building on flood plains so ‘innovative’ solutions were needed.

In an interview with The House magazine, he said: "We will never be able to say there should be a blanket ban on any building in the flood plain. "There's just so much of the country where that's an impractical restriction. What we need however to do is if someone is proposing to build in a flood plain they should be making what they are developing much more resilient against flooding.

"There are some really exciting things that are emerging. There's a rather wonderful technology in Holland where effectively you allow the house to float. It looks just like an ordinary house but all the connections are flexible and in the event that flooding occurs basically the house just lifts with the water… it's that sort of innovative thinking we need to be having more of."

Flood land

Image below: this shows in dark blue the Thames flood valley, an area where people want and need to live. It is well located between London and Reading, near Heathrow, and soon to be served by Crossrail. Yet new viable developments are being blocked on the basis of the current National Planning Policy Framework, which now needs to be reviewed and updated.

Large parts of Britain are flood land and there are a vast number of homes within such land. This is because historically villages, towns and cities were sited by rivers and coasts.

Existing properties tend to have either no protection against flooding or they have certain ‘flood resilient’ characteristics. Typical measures include raised ground floor levels; ‘sacrificial’ basements, storage areas and garages; raised electricity power sockets; flood resistant doors and windows; floor and wall membranes; one-way valves fitted to toilets and sinks; and so on.

Flood land is categorised as Category 1, 2, 3a and 3b (3b being the most extreme and classified as a functional flood plain). The existing policy is that any scheme proposed for flood zone land must pass a Sequential Test and then an Exception Test.

The Sequential Test determines that development should always be pushed away from a flood zone to nearby land that does not flood.

The Exception Test is applied if a proposed scheme passes the Sequential Test. The Exception Test determines if a scheme is satisfactory from a flood management and sustainability point of view.

The Sequential Test needs to allow for material considerations to be accounted for in any council deliberations. Some councils allow for this, and some do not, leading to inconsistent application of the test and uncertainty for the developer. The requirements of the Sequential Test need to be clarified to allow councils to consider properly the appropriateness of the proposals to allow common sense to be applied especially as new technologies have since become available.

Here is an example of a flood proof home, designed by Baca Architects, built near Marlow in 2016:


The amphibious house by Baca Architects demonstrated that, by working with the Environment Agency, one can build homes safely and responsibly within the flood plain.

Site design

Any new residential development must ensure unrestricted access for emergency services, and safe egress for residents. On a Kabina site this is achieved with raised roads and dry ramps:

Clearly, and rightly, safety is a prime concern. Interestingly enough, fully flood proof homes are obviously much safer than all the historic, non-flood proof homes that already exist in UK flood zones. Yet the government policies relate only to new homes being built rather than to existing properties. In other words, if 5.3 million conventionally-built houses are deemed acceptable, why aren’t purpose-built flood-adaptive homes?

Flood management

Flood management is another important consideration, particularly in functional flood plains. The sensible approach, as advocated by policy, is to ensure that any new developments do not make flooding worse where they are located. Also, they should not cause problems elsewhere by pushing the flooding to the neighbouring villages and towns.

Through comprehensive flood risk assessments and sophisticated flood modelling a technical solution can be provided for each site. This may incorporate the use of proven methods such as culverts, channels, swales, balancing ponds and flood cells, etc. This takes into account flood probability, flow rates and depths. One of the objectives is to ensure that the impacts of building in a flood zone are calculated and compensated for in terms of flood water flow and storage. In fact it may well be possible on certain sites to not only manage flooding effectively within the site but also take existing neighbouring homes our of flood risk by accepting their flood water.

An additional concern is that the debris that comes with a flood is predictable and managed effectively. Again, there are simple methods of dealing with this problem including the use of porous walls that act as filters.

The anticipated effects of climate change are also fundamental to proper planning and it is right that guidance includes allowances for this. Clearly any scheme and flood proof house design must take into account rising water levels. One of the great advantages of can-float homes with guiding piles is that they cater to any future flood levels.

All these considerations are intrinsic to the Exception Test. Government policy is well thought through and should be maintained and applied to ensure that any development is sustainable both socially and environmentally.

So the Exception Test policy and guidance currently used does not require further clarification.

Appropriate development

We fully support the principle that all inappropriate development should always be steered away from flood risk areas. However, attention needs to be drawn to the anomaly in the current draft of NPPF and its National Planning Policy Guidance (NPPG) which does not differentiate between a conventional dwelling and a flood proof dwelling. The guidance notes and its classification chart need to be updated to recognise this technology and the NPPF needs to be changed to allow these new safe proposals to be considered. Failure to do so runs the risk of the UK turning its back on appropriate development using engineering and technology already proven in many other countries, and increasing the pressure on Green Belt development to help achieve the Government’s housing targets.

Vulnerability

The table below is taken from government guidance. Zone 1 is the least extreme and 3b the most extreme.

Table 3: Flood risk vulnerability and flood zone ‘compatibility’


Key:
✔ Development is appropriate.
✘ Development should not be permitted.

The sensible and rational thinking behind this guidance is that development should be pushed up the table from Zone 3b to Zone 1 and that the 3b functional floodplain is not suited even to less vulnerable development.

What actually needs to change within this guidance is the definition of ‘less vulnerable’. We submit that ‘less vulnerable’ buildings include flood proof homes because such homes are designed to be safe within flood zones. Furthermore, we recommend that ‘less vulnerable’ buildings be permitted within Zone 3b.

A flood proof home that is considered by the Environment Agency to be safe, have safe access and egress, does not increase flooding elsewhere, is not a burden on emergency services and is supported by a site specific flood risk assessment should have the same classification as a conventional house.

The role of technology

Fundamentally the role of technology should be recognised in the context of UK policy. Recent discussions with the Environment Agency indicated that there is increasing acceptance that technical solutions exist. However the Environment Agency is currently obliged, for policy reasons, to ignore technology when advising on the Sequential Test.

This is why we recommend that sensible, practical, proven methods of creating desirable new homes in flood zones should be allowed. Therefore the Sequential Test should take into account modern house-building methods.

Koen Olthuis, adviser to Kabina and principal of Waterstudio NL, Rotterdam: “I’m designing floating communities, floating islands, floating mosques, floating apartment blocks, floating plug and play retail schemes all around the world. In this context building homes in English meadows where there is a one in 200 year risk of a one metre flood event lasting a week or so is not a problem.”

Pete Swift, Managing Partner, Planit-IE: “The time really has come for the UK to recognise the benefits of building in flood zone land and accept that there are easy, proven and established technologies available to make this highly safe and sustainable”.

Guy Lane, Marketing Director, Kabina Ltd: “There is not much wrong with the National Planning Policy Framework. The problem is that it is being interpreted and applied in such a way as to stymie sensible development proposals in flood zones. So let’s review the NPPF Guidance so that flood proof homes are deemed ‘appropriate’ and not ‘vulnerable’.”

For more information please contact

Guy Lane, Marketing Director,
guy.lane@kabina.co
tel 07798 832576
www.kabina.co

Kabina Ltd
13 Hawley Crescent
London
NW1 8NP
Kabina is a registered trademark.

Editor’s notes:
Neil Cheston and Guy Lane founded Kabina, a UK company, to work with water not against it. Our ethos is to deliver economic, social and environmental benefits through intelligent innovation. Kabina’s essence is ‘Of our time’.

Kabina's diverse and expert team includes acknowledged naval architects; real estate professionals; urban planners; offsite housing manufacturers; and environmental specialists.

Kabina® is responding to well-documented and accelerating trends: climate change; unprecedented weather events and their consequences; and the need to build new homes for the 21st century.

Kabina’s new flood adaptive smart homes can

  • 1) Make a strong contribution to the UK’s post Brexit economy;
  • 2) Provide net contribution to UK flood mitigation;
  • 3) Reduce construction costs and time, subject to the planning process;
  • 4) Help to resolve the current acute housing crisis;
  • 5) Support 2017 Autumn Budget and Housing White Paper policy objectives; and
  • 6) Reduce UK plc's flooding risk because of climate change.

Ends/

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Get in touch

Guy Lane
Marketing Director
: +44 (0)7798 832576
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Kabina Ltd

13 Hawley Crescent,
London
NW1 8NP