THE cost of flood damage could rise to more than £20bn a year unless radical changes are made to flood management policies, it has been warned.

The risk of disasters like those that struck North Yorkshire and the North-East less than four years ago could increase 20-fold over the next 100 years if nothing is done about the way the threat is handled.

In 2000, rivers and becks in North Yorkshire burst their banks and turned much of the county into a lake.

Last Monday, parts of the county were on flood alert again after days of rain left water courses overflowing.

The national report, drawn up by a 60-strong team, found that if expenditure and approaches to flood management were left unchanged the risk of flooding could increase and the number of people affected could rise from 1.6m to between 2.3m and 3.6m by the 2080s.

The report also said the cost of flood damage could be reduced if carbon dioxide emissions were reduced by up to 25 per cent and if building projects in high risk areas were carefully managed.

Maintaining the current level of flood risk could cost between £20bn and £80bn over the next 80 years, but a steady increase in investment of between £10m and £30m a year for that period would make future flood management more affordable.

Sir David said: "There are currently about £200bn worth of assets and 1.7m properties in flood risk areas in England and Wales.

"The scenarios in the Future Flooding report may seem a long way off, but the challenge of increased flood risk needs to be considered now."