The Gloucestershire town of Tewkesbury was inundated in 2007
Flooding in parts of England in the summer of 2007 cost the economy £3.2bn, the Environment Agency has said.
It also calculates that investment in flood defences will need to almost double, to £1bn a year, to protect properties in the future.
Thirteen people died and hundreds had to be rescued after parts of South and East Yorks and Gloucestershire flooded.
Around 48,000 homes were affected, each costing between £20,000 and £30,000 to repair, the agency added.
The cost for flooded businesses averaged between £75,000 and £112,000.
While almost every business was adequately covered by insurance, the agency said a quarter of affected homeowners were not fully insured.
Other calculations published by the agency showed that farmers lost an average of £1,150 per hectare of land flooded, while the cost of damage to infrastructure such as roads, water supplies and power networks was put at £660m.
The report also factors in damage to communications, transport and roads of around £230m, with costs to local councils of £140m, while agriculture suffered losses of £50m.
The agency adds that 400,000 pupil days at schools were lost because of the floods in June and July 2007.
Robert Runcie, Environment Agency director of flood and coastal risk management, said: "The 2007 flood cost homeowners, businesses, emergency services and others some £3.2bn.
"The high costs of flooding underline the importance for continued investment in reducing flood risk, particularly as climate change means that we are more likely to see more severe and frequent flooding in future."
The costs of the more recent flooding in Cumbria, which saw road bridges destroyed by rising river levels, would not be known for some time, Mr Runcie said. But he warned the cost would be "substantial".
And the Environment Agency is warning that the average annual cost of flood damage could rise by 60% by 2035, unless funding for defences is doubled to £1bn a year by then to protect against climate change.