Protecting properties against floods

This Issue This is a part of the Resilience feature

By - , Build 148

Surface water flooding is increasingly affecting millions of homes in the UK and Europe. Property level protection has been advocated and a six-step process developed. Could this be an option for New Zealand?

Figure 1: Wet testing of door and window guards.
Figure 2: Demountables in action at Bewdley, Worcestershire, UK.
Figure 3: Six-step process for property level protection.

OVER THE PAST few decades, flood events in Europe have changed, and as a consequence, the way that excess water is managed has changed too.

Problem of surface water flooding

Taking England as an example, there are around 23 million homes. Of these, 6.9 million are now identified as being at risk from flooding, up four-fold over the last 10 years, and it is the nature of the increase that has proved most challenging.

From being unrecognised a decade ago, surface water flooding from inadequate drainage is now the major source of flood risk in the UK. This is a growing trend in many European countries as rainfall events become more intensive, consistent with climate change predictions, coupled with a gradual intensification of urban areas.

Floods are no longer something to hold back behind walls next to rivers. They need to be managed differently, and resilience needs to be built into towns and cities.

Potential for property level protection

Due to this shift, the potential for utilising property level protection (PLP) is now advocated in the UK. Although the term refers to individual properties, it also encompasses the use of technology that can protect on a community scale.

PLP can keep water out of buildings or local areas. If ingress does occur, it can limit damage and speed the recovery of people and places. For instance, the use of material that is resistant to water damage enables people to move back into their home much more quickly and reduces the costs of refurbishment.

Innovative solutions

Innovative technologies may encompass aspects such as door guards (see Figure 1), demountable barriers or air bricks that are able to resist the entry of water to homes to a depth of around 600 mm and in some cases significantly higher.

Figure 1: Wet testing of door and window guards.

On a community scale, perimeter barriers may also be deployed in either a temporary or automated fashion to protect areas. Figure 2 shows a demountable scheme in Bewdley, Worcestershire, UK, that can hold back floodwaters up to 3 m in height.

Figure 2: Demountables in action at Bewdley, Worcestershire, UK.

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Property level protection uses

PLP is particularly useful where:

● there is uncertainty regarding the degree of risk

● buildings are of high value or part of our critical infrastructure

● settlements are remote and do not justify expensive capital projects

● there is a history of inadequate drainage or a drop in ground levels as occurred in Christchurch after the earthquake.

New field brings concerns

Despite the potential of PLP, it has not been in common use. The European Union FP7-funded SMARTeST project was funded to improve its contribution to flood management.

The research established that the problems stemmed from a lack of trust in an emergent field. Common concerns were:

● how products and companies can be compared

● how to match the right product to the right risk

● how to ensure that the technology will be installed and maintained correctly.

No best-practice guidelines

It became clear that there are no best-practice guidelines for selection, installation and maintenance of PLP anywhere in Europe.

Although people could see its potential, they had insufficient information to make a decision on using PLP, with a clear lack of expertise freely admitted even among flood risk management professionals.

To address this, a voluntary code of practice for the UK was co-produced with government departments, local councils, regulators, flood risk consultants, product manufacturers, community flood resilience forums and the general public.

Two separate guidance documents were developed:

● A comprehensive version for local authorities and professional flood risk managers.

● A simpler version for property owners.

Six steps identified

In both versions, six sequential steps were identified, beginning with understanding the risk through to operation and maintenance (see Figure 3).

Figure 3: Six-step process for property level protection.

Step 1 provides guidance on knowing the risk, giving links to official maps to enable the specific flooding threat. If this suggests that there is a risk, stage 2 helps users to consider and plan a scheme, find out about the range of products available and think about individual requirements.

If a decision is taken to proceed, the following stages extend this logical process and cover information on survey, design and installation, right down to the final aspect of operation and maintenance.

At all stages, the guidance is simple and impartial and provides links to further sources of information and references if required.

Since its development, the guidance has been endorsed by many organisations. It has also influenced wider policy and practice by, for example, informing the update of PLP standards (PAS 1188) issued by the British Standards Institute.

The research has also contributed towards the development of new surveying protocols for PLP technologies and a property flood resistance database for the insurance industry.

Replicating the six steps in New Zealand

Although this guidance will not be directly applicable to New Zealand because of its different regulatory circumstances, the principles and methodology of the six steps approach is replicable.

The next move is for the extent of the threat of surface water flooding to be recognised in New Zealand and for the guidance to be considered in this unique policy context.

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For more

Further information on the six steps is available from the Smart Flood Protection website at www.smartfloodprotection.com.

Download the PDF

More articles about these topics

Articles are correct at the time of publication but may have since become outdated.

Figure 1: Wet testing of door and window guards.
Figure 2: Demountables in action at Bewdley, Worcestershire, UK.
Figure 3: Six-step process for property level protection.

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