Housing stock in areas where flooding is likely at least once every 30 years has grown at a rate of 1.2 per cent per year since 2011, according to analysis by the Committee on Climate Change (CCC). By contrast, housing outside of flood plains – in areas with less than a 1-in-1,000 year chance of flooding – increased by an average 0.7 per cent a year over the same period.

Lord Krebs, head of the CCC’s adaptation sub-committee, said: “We are building faster in the flood plain than anywhere else.

“If the planning system is going to allow people to carry on building in the flood plain, we have to be aware we are storing up problems for the future because flooding is going to get more frequent.

“So you are locked into cycle of building and having to defend, and then having to build bigger defences because the flood risk has increased.”
On current trends up to 20,000 houses are likely to be built this year in flood risk areas.

Lord Krebs said he expected about 4,500 of these to be medium or high risk areas, where flooding is expected at least once every century.
Many of these are being built with the Environment Agency (EA)’s approval because they are behind existing flood defences, which the agency judges provide adequate protection, he said.

But such protection may not be adequate in future, with defences already being overtopped in recent weeks by “unprecedented” floods. “Today’s unprecedented may be tomorrow’s norm,” he warned.

Thousands of other homes in at-risk areas may be being built without the EA’s oversight because they are in small developments of less than 10 houses, he said.

Lord Krebs warned the continued spread of concrete and paving tiles over gardens and other green spaces was worsening the risk of flooding because it prevented water draining.

Farmers and grouse shooting estates had also increased the risk for urban areas by draining peat bogs on surrounding uplands, which used to provide a natural “sponge” for rainfall.

Senior EA officials have been among thousands of social media users to share a photograph in recent days showing flood waters lapping around a sign marking a development site with permission for 39 new homes, near Whalley in Lancashire.

But documents reveal the EA did not object when consulted by council planners on three applications for the development.
In two cases it made no comment, while in one case it said it had “no objection in principle”, only proposing conditions of sustainable drainage for the new homes.

The agency did raise concerns about an earlier plan that extended into the official flood risk zone, but waved through a tweaked plan that would see houses built immediately abutting the flood zone.

Photos appear to show that flood waters in recent days have extended at least to the edge of the proposed development site.

When the Telegraph attempted to contact the applicant for the development, his wife claimed the picture was “misleading” because the proposed houses were not to be built right by the sign, and were not due to be built “on what the Ribble Valley says is the flood plain”.

She would not confirm whether the flood waters had however extended into the area designated for development.

Ministers on Tuesday announced a further £50 million funding for local authorities to help support households and businesses affected by this weekend’s floods.

Greenpeace UK researchers used details obtained through Freedom of Information requests to plot the location of these housing zones, and cross-referenced this with flood risk maps from the Environment Agency.

They found around nine of the 20 zones, comprising a total of 9,000 planned new homes, are in areas now identified as being partially or fully at risk from flooding. Under the terms of a new government flood-insurance scheme soon to be implemented, these properties would be excluded from cover.

This would leave homeowners reliant on commercial insurers who may choose not to insure homes built in flood zones, or do so at prohibitively expensive rates.

A spokesperson for Flood Re confirmed to Greenpeace that ‘properties built from 2009 onwards’ in flood-risk areas are still excluded from the government scheme, adding: “It would be irresponsible to incentivise developers to build in such areas simply because those properties could have their insured flood risk ceded to Flood Re.”

Greenpeace UK also obtained new figures showing that the number of people employed by the Environment Agency to work on Flood and Coastal Erosion Risk Management fell by 230 – a 5% cut – in the last three years. The agency plays a key role advising councils on flood risk.

Greenpeace UK chief scientist Dr Doug Parr said: “The current flood emergency isn’t even over yet, and the government is already storing up the next one. Rushing to build thousands of new homes in flood-risk areas whilst at the same time cutting flood protection staff is a recipe for disaster.

“David Cameron’s lofty rhetoric at the UN climate summit is helpful, but if he’s serious about protecting Britain from the impacts of climate change, these words need to translate into climate-savvy policies on the ground.

“When it comes to energy, flood defences, and other big infrastructure projects, we need the government’s hands to start following what the government’s mouth is saying rather than acting of their own accord.”

Prof David Balmforth, a former president of the Institution of Civil Engineers, said that conventional defences, such as the barriers that line the river Greta in Keswick, had to be supplemented with more innovative methods.

We tend to design defences to a particular standard, to give an annual probability against flooding, which might be, say, a one-in-100- or one-in-200-year chance of the defence being overtopped,” he said.

“That would be a typical sort of figure that would be used. The question that now remains is: were the events that we’ve now seen in recent days so excessive that it’s reasonable to expect them to overtop defences?

Suggesting ways of coping with future deluges, Balmforth cited work that was done in Nepal. He said: “They have regulated minimum threshold levels about a metre above surrounding ground for any new major development, whether or not it’s in a flood risk area.”