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Debate Flood solutions

Floods continue to wreak havoc across our and countryside urban areas. But can engineers deliver flood-busting solutions whatever the weather?

This week we ask: Is flooding inevitable?

Yes

Hilary Aldridge, area manager for the Anglian region of the Environment Agency

It is impossible to guarantee flood protection. There are many locations where an engineering solution is impractical and others where permanent work could lead to considerable damage to the environment.

Even where flood defence is provided, there will be occasions when conditions are so severe that the defence is overwhelmed.

History shows that although civil engineers have designed some magnificent flood defences, there is always a flood which exceeds design. And designing solutions is all about risk. Engineers have difficulties in assessing and managing low frequency, high consequence events, such as flooding.

Flooding occurs from a variety of sources: sea, rivers and streams, urban run-off and overflowing drains and sewers.

Put this in the context of low lying land - for example, 20% of East Anglia is below mean high tide level - the rise in sea level due to the polar ice caps melting, and the overall increased unpredictability of the weather due to global warming and you can see why the task of defending everyone from flooding is a huge issue. It requires many organisations to work together.

Proper funding is crucial.

One of the key elements in flood management is raising awareness. Not only can we improve the flood warning system, but we can advise local authorities and individuals of high risk areas and urge developers not to build future developments in the flood plain. The Environment Agency's programme of new defences and maintenance works continues in line with appropriate priorities.

But increasingly, we are looking for ways of working with, not against, nature. The coastline, for example, is so dynamic that we cannot fight erosion. Instead, we are concentrating on techniques such as the re-creation of saltmarshes, particularly on the Essex coast, which will act as a frontline defence.

Flooding is inevitable, but we can work in harmony with the environment to mitigate the effects and provide sustainable solutions.

No

Haydn Evans, managing director Haydn Evans Consulting

I do not deny the possibility of global warming and the subsequent rise in sea levels. I do not know if we are facing long term global cycles between ice ages, or medium term climate fluctuations.

But all a civil engineer needs to know is the parameters he or she has to design within. And the technical solutions to these problems are not new. Our Victorian predecessors, whose starting point was mud, filth and chaos, valued civil engineering above almost anything else.

Think of Telford and Brunel, Vermuyden with the huge undertakings in the Fens, Bazalgette and the Victoria Embankment in London.

From the beginning British engineers developed expertise in the modelling and analysis of flooding and the design of control measures. These skills have been valued highly and exported worldwide.

What are these methods?

Tidal flooding can be held at bay by sea walls. Fluvial flooding prevention is no less straightforward, especially with vastly improved river catchment modelling techniques. In some areas we can dig out the downstream river to make it deeper and wider. Look at the new diversion channel being built on the Thames at Marlow.

We can raise river walls. Name a height and I will design you a brick, concrete, steel or earth barrier. It may spoil attractive waterfronts, it may require land purchase, it may be downright ugly - but it is possible.

Sometimes, we can go upriver from the town and build a barrage. Best of all, we can go even further upstream and practise catchment management throughout the system and introduce retention and storage.

But whatever the scenario, there is a design solution.

The facts

Scientists predict that a dozen serious floods a year could become the norm in Britain as a result of global warming.

So far, the Government has pledged an extra £51M to improve flood defences.

Last year's floods - in some areas the worst for 400 years - were responsible for two deaths, left 7,406 properties flooded, and caused an estimated £1bn plus repair bill.

The Environment Agency's website gives you the opportunity to see if your home is at risk from flooding at www.environmentagency.gov.uk. Enter your postcode at 'What's in your backyard?'

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