Plans for a new Thames barrier are being considered by ministers, amid fears that global warming will increase the threat of London succumbing to floods.
Proposals for a £20bn system of flood defences to the east of the current Thames barrier at Woolwich are being drawn up as part of a series of measures to protect the capital from rising sea waters.
One proposal being studied suggests a major new barrier at Sheerness in Kent. But Environment Agency officials are also considering opening up land east of London, making them emergency flood plains as part of long-term proposals to alleviate future surges in the river.
Rising sea levels due to global warming are increasing the threat of London being inundated by floodwaters. The Thames barrier is designed to offer protection against a one-in-2,000-year chance that the capital will flood. But, by 2030, the chance of flood defences being overwhelmed will be halved to one in 1,000 years.
Phil Woolas, the environment minister, used an interview with the Sunday Telegraph to warn that extreme weather was now a "real threat".
He said: "People accept that is is a real threat but they don't realise the imminence of it. Hopefully, if there is any good that comes out of the floods it will be that recognition."
Ministers are due to receive an update on London's long-term flood defences in the next few weeks. A formal decision on the future of flood protection for the capital is to be taken in two years.
Fears about the flood risk in Britain have been heightened by the devastating floodwaters that hit many parts of Britain this summer. In Gloucester, Mr Woolas warned that the Government would have faced the "biggest peacetime evacuation in history" had the emergency defences around the Welham electricity sub station failed.
A report published earlier this year by emergency planning officers gave a graphic illustration of the effect of a huge flood on the areas to the east of the Thames Barrier. The London flood response plan warned: "Because of climate change, both the chance and consequence of flooding are increasing. Sea level rise, more frequent and higher storm surges and increased winter rainfall and more intense summer rainfall will add to the existing risk and it may not prove possible to improve fixed defences sufficiently to maintain or raise protection standards."
The report warned that a one-in-1,000 year flood could produce surges of water strong enough to sweep people off their feet and leave parts of east London with floods "several feet deep in places". But a spokeswoman for the Environment Agency insisted that protection against a one-in-1,000 year flood still represented "a very high level of flood protection".
She said the Thames Barrier and other flood defences would continue to protect London until 2030 but said the agency had to look at possible improvements to cope with potential changes into the next century.
Chris Huhne, the Liberal Democrat environment spokesman said the Government was doing too little to counter the dangers. He said: "This is belated recognition that the Government has seriously underestimated the risks of flooding by failing to take into account the worsening outlook caused by climate chaos."Reuse content