Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

The case for the defence

An ICE commission is to review UK flood defences after many failed to stand up to the winter storms. Its chairman Professor George Fleming has firm ideas on what needs to change. Nina Lovelace reports.

The insurance bill for the floods that devastated Britain over the autumn and winter will top £1bn, the Association of British Insurers claimed last week.

The worst flooding that the country has seen in over 50 years has left many asking 'how could we be caught out like this? Will next winter see the same?'

Faced with the threat of further catastrophes, the Government has launched a major flood policy rethink.

Government reviews on flood defence policy and funding were set up at the end of last year and last month the Ministry of Agriculture Fisheries & Food appointed the ICE to carry out an independent review of the technical issues of flood defence.

'We wanted to do some navel gazing and ask ourselves if the techniques we use are appropriate based on last winter's floods, ' says MAFF's chief flooding and coastal defence engineer Reg Purnell.

Fresh from the challenge of revolutionising the ICE's membership rules, past president Professor George Fleming now heads up the six strong commission to recommend how flood defence techniques need to change.

The commission's first meeting last month discussed how to stage the review and what flood defence issues need investigating.

This will include assessing how seriously the Environment Agency and local authorities consider future climate change in their flood defence strategies.

'We don't know that people are taking this into account, ' says Fleming, although he himself is in little doubt that climate change is a reality. 'The Meteorological Office has been predicting increased rainfall and flood events for some time.'

This raises the question of whether current flood defences - designed using historical flood data - are just storing up problems for the future.

'Our flood defences are designed to a 1 in 100 year flood risk based on historical data. We should see that by 2050 that 1 in 100 year flood risk will actually be reduced to a 1 in 50 risk, ' says Fleming.

'Therefore defences we design now that have plenty of capacity will be undercapacity in 50 years' time.'

Instead, he says, engineers should be doing something they have been loath to do in the past - overdesign for the present.

'Instead of building a 1 in 100 year flood risk defence, we should instead be building to a 1 in 200.' He adds that there is a need for national consistency to create best practice in design.

Some defence against the 1 in 10,000 year flood of biblical proportions should also be included, such as flood walls that work with nearby washland areas to store extra flow, he says.

'We must accept damages above the designed event, ' he says, 'but we need to ask ourselves what we need to build into that design to see that lesser risks are managed for.'

Fleming also hopes to gather information on newer types of flood defence systems that work with the environment - such as flood diversion tunnels, washlands and recent innovations such as temporary flood defences. These are only put up when flooding is expected - making them perfect for riverside residential areas that want to retain their river views.

The commission will also be investigating whether the UK can develop a more strategic approach to flood defences over a wider geographical area, essential if flooding events are to be properly estimated and managed, says Fleming.

'What's the point in building a new culvert upstream when further downstream there is an ageing under-capacity culvert that will simply flood?' he says.

He hopes to discover if initiatives such as catchment area management systems to manage flood defence over larger areas are having an effect.

The commission will also look at flood modelling techniques to see if they take account of changes to an area through forestation or urbanisation.

'I am an advocate for deterministic modelling, that investigates for instance how land use affects run off, ' says Fleming, 'However it has never been part of core best practice, so is not a standard for forecasting.'

Fleming is also concerned that flood forecasting is often hindered because prediction information is not used as well as it can be.

Modern weather forecasting tools are very efficient and can pinpoint often small areas that will receive reasonably large amount of rainfall. Putting this together with past experience, for example knowing that the land is already saturated, can give councils and the Environment Agency fair warning that a flood will occur and give them more time to prepare.

Instead, Fleming complains, the events are dealt with after they happen.

'That's not flood management, that's crisis management, ' he says.

'We should be able to predict in advance what the vulnerable areas are, and protect them.'

The commission also includes more hands-on flood defence engineers such as Mott MacDonald's Charlie Rickard.

'My input is on the practical side of flood defence engineering, ' says Rickard. 'The next step is to consult with everyone from the RSPB to Railtrack as well as getting views from those directly involved such as the Environment Agency and local councils.'

Rickard is keen however that the Commission does not simply repeat work done by others, such as the research and development review currently being carried out between the Environment Agency and MAFF. 'Otherwise we may end up with something rather superficial, ' he says.

The commission has planned a further six meetings within the next few months. Its draft report will be published in September with the final version expected in December.

Findings will be also go to ICE members and government through seminars, publications, books and journals, with the aim that their discoveries may also inform future engineers' flood design training.

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.