More than half a million homes and businesses will be at “significant” risk of flooding in the future without more investment in flood defences, the Government's advisers on climate change have warned.
Floods which have had a devastating impact in the past few weeks are likely to become more common in the future as the climate changes and increases the chances of extreme weather, Lord Krebs of the Committee on Climate Change said.
But a funding gap of almost £1 billion is opening up between what is needed to keep properties protected in the face of climate change and what is being spent over the next few years.
At the same time an increasing number of homes and businesses are being built on the flood plain, with 40,000 properties constructed without community flood defences in the past decade - putting them at a significant risk of flooding.
And the risk of surface water flooding is on the rise because people are increasingly paving over their gardens, giving rain nowhere to seep away, with the area covered by hard surfaces almost doubling to around half of garden space.
Lord Krebs suggested the way to tackle the increase in hard surfaces, up from 28% to 48% of urban gardens in a decade, was to "get TV gardeners to tell people to stop putting down decking and paving and have lawns instead".
He said the Government needed to support more investment in flood defences or find other ways of managing the social and economic costs of more flooding which could require explaining to people they have to accept a greater risk of floods.
Around 610,000 properties will be at significant risk of flooding by 2035 without action, four times more than if there was increased investment in flood defences and more careful planning of new housing in the flood plain, the committee said.
The Environment Agency has warned it needs a year-on-year increase of £20 million for flood defences on top of inflation to maintain the current level of protection.
But flood defence spending is 12% below what it was in the last spending review period, with a gap opening up of £860 million between what has been pledged for 2011-2015 and what is needed to keep the same number of properties protected.
A report from the committee said the shortfall in funding could be made up from private or public sources.
But "third-party" investment by local authorities or businesses would have to increase from £72 million already secured to the £860 million level to keep pace with climate change.
More than 200,000 properties have been built in the flood plain between 2001 and 2011, of which 40,000 are at significant risk of flooding because they are not protected by flood defences.
And the take-up of protection measures for individual properties, such as flood guards for doors, is up 35 times lower than it would need to be to safeguard all properties that could benefit.
Lord Krebs said: "Flooding, as we have seen recently, can have a devastating impact on people's lives and livelihoods.
"How we adapt to these risks will be critically important to our future resilience: whether it's deciding not to pave over our gardens; or building in less exposed areas."
The report's message to Government was, he said: "You, government, have got to either find greater contributions from third parties - local authorities, private sector - or contribute more yourself or you've got to find a plan B maybe to explain to people 'I'm sorry, you're on your own, you've got to accept a greater risk'."
The report on adapting to climate change, which comes after the final hosepipe bans introduced in the face of drought across much of England were removed following record rainfall, also said water resources were likely to become more scarce in some areas.
While demand for water had been cut slightly, more could be done, including increasing the use of water meters, particularly in high risk areas, and water efficiency measures.
A spokesman for the Environment Department said: "The committee has acknowledged the work we have done to reduce flood risk for 182,000 homes over the last three years.
"We are spending more than £2.17 billion over four years to protect people from flooding and our successful partnership funding model will draw in around an additional £72 million.
"The money for flood defences is being spent more effectively than ever before and we now expect to exceed our target to better protect another 145,000 homes by 2015."