Flood protection 'needs doubling'
One in six homes in England is at risk of flooding, says the Environment Agency, and climate change will raise that number without better protection.
The agency calculates that funding for projects that protect communities from flooding from rivers and the sea needs to double to £1bn annually by 2035.
Without that, it says, economic damage worth £4bn per year could be the norm.
The agency's report uses data from the government's projections of UK climate impacts, published on Thursday.
Geoff Boyd, Environment Agency: "Big decisions to be made about flood risk"
"The latest UK climate change data shows that the risk of flooding and coastal erosion will continue to increase in future due to rising sea levels and more frequent and heavy storms," said agency chairman Chris Smith.
"There are important decisions for us all to take about how to manage these risks to protect people, communities, businesses and the economy in future."
The climate impact projections - UKCP09 - concluded that every part of the UK was likely to receive more rainfall in winters - by 2080, as much as 20% more in some regions.
AREAS MOST AT RISK OF FLOODS
1. Boston District
- 23,700 properties
2. North Somerset
- 20,415 properties
3. East Lindsey District
- 14,949 properties
4. Windsor and Maidenhead
- 11,477 properties
5. City of Kingston upon Hull
- 9,825 properties
6. Shepway District
- 9,065 properties
7. Sedgemoor District
- 8,092 properties
8. East Riding of Yorkshire
- 7,513 properties
9. Runnymede District
- 7,007 properties
- 6,533 properties
UK 'must plan' for warmer future
This means, the Environment Agency says, that rivers may carry 20% more water at some periods of the year than at present.
The agency is also concerned that rising sea levels may overwhelm sea defences in some regions unless they are strengthened.
Vital infrastructure is also increasingly at risk, it says, with about one-sixth of the country's electricity infrastructure situated in flood plains.
The agency revealed the top 10 local authority areas in England with the most properties at risk.
Top of the list came Boston, in Lincolnshire, with 23,700. Second was North Somerset with 20,415 and third was East Lindsey, also in Lincolnshire, with 14,949.
A year ago, the Pitt Review of flood preparedness concluded that major improvements were needed at local and national level.
Sir Michael Pitt said it was "absolutely not acceptable" that residents were forced out of their homes for more than a year by flood damage.
But he did not name the cost of improved flood protection - a gap that the Environment Agency has now filled.
It suggests that some schemes could be funded locally without input from central government.