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Page last updated at 10:37 GMT, Thursday, 16 August 2007 11:37 UK

London's drowning

House of Parliament, London Eye and other landmarks under water
London overwhelmed by a huge tidal surge in The Flood

By John Walton
BBC News

With this summer's torrential downpours still fresh in the memory a new 25m disaster movie, The Flood, charts the devastation of central London. It's a dramatic vision, but could it really happen?

It started out as a Hollywood-style disaster movie, but following the floods in Gloucestershire and Yorkshire this summer, Tony Mitchell's movie The Flood has the sound of something a little closer to real life.

London floods in 1928

As time passed the feel of the project began to change and, "science fiction soon became science prediction", Mitchell has said.

The experts, though, disagree. Speaking for the Environment Agency, Rachael Hill says the film has a lot more fiction than fact, especially as far as "overtopping" London's main flood defence, the Thames Barrier, is concerned.

"If you had a tsunami coming up the Thames that would overtop the barrier, then that water would have spread out along Kent and Essex, or gone round either side of the barrier," she says.

The risks

Illustration of flooding

But that's not to say floods along the Thames Estuary aren't a very real problem.

The threat has been with us for centuries. The most recent major disaster took place in 1953 and saw over 300 people killed. It was this flooding of Canvey Island and the east coast that inspired the construction of the Thames Barrier, which was in position 30 years later.

The threat of flooding is slowly increasing as time passes. Climate change is raising sea levels on the one hand, while on the other London is feeling the effects of subsidence, and is sinking a couple of millimetres each year.

In addition, climate change also makes storm surges both more likely and increasingly unpredictable.

See the Thames' flood plain, home to over a million people

But Ms Hill says this is all being planned for by the Thames Estuary 2100 project, for which she is the technical strategy manager.

The project has the job of planning the flood management of the Thames for the next 100 years. Their working estimates for sea level rises during this time period span anything from under 1m (3ft 3in) to some of the most extreme global warming predictions that would see sea levels rise by as much as 4.2m (13ft 9in).

"That 4.2m scenario is almost the sort of Al Gore scenario of the worst thing that climate change could do, including the demise of the arctic ice sheets, and everything else, so that is very much the extreme event," she says.

"But we need to make sure we are planning across those scenarios. So our plan is realistic, but it can also be adaptable through this century."

The barrier

Thames Barrier: Still from the film, The Flood
Occurs when low pressure in Atlantic pushes towards the UK
Sea forced above normal levels, creating hump of water
Hump moves down east coast and funnels into Thames Estuary
Water levels increase, and can rise further if combined with high tide
Surges to become more frequent and less predictable
But what about the Thames Barrier itself? It was defeated by The Floods fictional storm but how will it fare against the real storms and tidal surges of the future?

Ms Hill predicts that the barrier will stand firm: "We certainly know that there will not need to be any major changes to the Thames Barrier.

"We don't anticipate any major engineering projects in the Thames Estuary before 2030. If we use the barrier in combination with other options - such as flood storage [see below] - we know that the barrier will be effective up until 2100."

She also believes any talk of the need for a second barrier in the river is premature. "It is still one of the things we are looking at, but it certainly isn't being fast-tracked as a result of any of the recent flooding," she says.

"If climate change did throw at us this 4.2m [rise] on top of maximum water levels then an outer estuary barrier would be the only solution that would be effective.

"Because we are planning for something more realistic, something around 1m, there are much more sustainable solutions that we will look at first."

Making space for water

Flood resilient housing
Houses should have at least two storeys, so people can evade rising water
Use basements as garages or utilities rooms, not bedrooms
Build with brick not timber
One of these solutions is flood storage. The idea is simple. In order to stop flood waters overwhelming central London and to save the massive expense of building fresh flood walls and defences, some land could be set aside to act as a safety valve, catching flood waters and storing them until the danger has passed.

The most likely spots for flood storage are between the barrier and Tilbury, to the east. Ms Hill suggests that any land ear-marked for future flood storage could be used as farmland, playgrounds, parks or nature reserves when not called into action to take the edge off tidal surges.

These are the sort of ideas Ms Hill would like to see employed as the redevelopment of the Thames Gateway area gathers pace.

She says: "The majority of developments throughout the Thames flood plain at the moment really don't take account of the fact that they are in a flood risk area, so redevelopment is about making things better."

Turning from the real world of flood management and back to the big screen version Ms Hill has more words of re-assurance: "We are not planning for the scenario they are presenting, as it is so very unlikely, but it's going to be good popcorn viewing."

The Flood is due to be released on 24 August.

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Add your comments on this story, using the form below.

Ho ho ho. Fact check needed. London is going to be very very vulnerable by 2030, even without "global warming" effects such as an increase in localised violent weather. But admitting that in public might force the country's south-east-centric rulers to face the inconvenient truth that the UK's capital, and the people and organisations based in and around it, are heading for deep trouble in this generation's lifetime. It's time attention moved away from London and the south east, otherwise it'll be very expensive and very inconvenient. South east house price crash? You ain't seen nothing yet.
Phil Junod, Birmingham, England

Amazing how readily much money is spent on preventing London flooding, something that is very rare and how little is spent on preventing places that regularly flood.
Eddie, Edinburgh

How come I've never heard of this movie? It isn't even on It looks amazing. It's no wonder the British film industry is in such a bad way. They can produce movies to rival Hollywood but their PR sucks.
teegee, Belfast

All of the above is fine for the people living in London, what defences are being made to ensure floods like this years are not repeated along other rivers. Gloucestershire aswell as Yorkshire was badly hit, what defences will we be provided with?
, Sheffield, UK

Will the Thames barrier protect the Lea Valley if a 1m sea level rise ocurrs? It is interesting that the IPCC report findings published in January thus far aren't reflected on the Enviroment Agency web site. Is this going to be updated at any point?
James, NE London

This film has already been released. I watched it about 4 weeks ago on spanish TV. It is very realistic and made me glad to have taken my grandmothers advice and lived on a hill!
Sue Schubert, Malaga, Spain

Could large ammounts of sand & River debris being washed onto the submerged gates cuase them to fail?
Mick Franks, Littlehampton

When New York flooded recently, the water didn't come from a tidal surge. Never underestimate the power of nature nor overestimate the strength of mankind in fighting nature. We're not half as clever as we think we are. Man the destructor will one day be easily destroyed, either by heat, cold or water. Might as well carry on partying in the meantime.
Hans Schreuder, Ipswich, UK

"flood storage" - some land could be set aside to act as a safety valve, catching flood waters and storing them until the danger has passed. Isn't this what flood plains are all about? If we hadn't built on them in the first place we wouldn't have re-create artificial "flood storage"?
Andrew Kirkby, Harrogate

Always reminds me of "Goodbye Piccadilly" a book of the early seventies where a terrorist group ( white ultra nationalists)plan to blow the Staines Reservoirs to coincide with a 1953 style Hump. I guess this film will be as accurate in its fulfilment as that book.
Tony Jackson, Welling Kent

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video and audio news
An interview with the director of Flood

London's small but relentless dip
12 Jul 07 |  Science/Nature
On the rise: The Thames in 2100
13 Jul 06 |  Science/Nature

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