Flood is the greatest risk to the UK, and it is increasing. Rising sea levels without real spending on defences and more mitigation would increase the likelihood of another event of the severity of the 1953 North Sea flood. This was the theme that emerged from the panel discussion on UK flood risk management.

In 1953, more than 300 people died in the UK and 24,000 properties were seriously damaged when the combination of an exceptionally high tide and tidal surge overwhelmed sea defences and caused extensive flooding in the eastern part of the country.

It was, said Jane Milne, climate change manager for the Association of British Insurers (ABI), a one in 200 or one in 250 year event, but if the same atmospheric conditions reoccur as the sea levels rise, it will happen again.

Studies by the ABI show that with just a 0.4m sea level rise, 400,000 homes on the east cost - equivalent to 750,000 people - would be at a severe risk of flooding plus two-thirds of electricity stations, 20% of hospitals, sewage plants and police, fire and ambulance stations, and 15% of schools.

Through the ABI, insurers have been campaigning for more Government spending on flood defences. The ABI has called for an increase to £750m by 2011 in place of the current £570m. Last year, The Treasury ordered the Department for Environment, Food and Rural Affairs (Defra) to shave £15m off its flood defence maintenance budget for 2007/2008. The ABI slammed the move.

“Future increased flood risk is inevitable,” said Bill Donovan, climate change policy advisor for the Environmental Agency. He said there was some evidence of accelerated sea level rise in UK coastal waters during the 1990s. Today, about one-third of the English coastline is fronted by hard defences. It could be that in future, some parts of the coast would be abandoned to the flood risk. He said: “In the long term, big decisions have to be made. We have to try to work in a sustainable way to protect the environment.”

For river flood, the picture is less clear. Climate change may also increase the urban flood risk by intensifying rainfall, and 40% of flood damages come from intense rainfall in built up areas. So far, however, said Donovan, there is little clear evidence for change of peak flows in rivers.

Neil Mercier, head of property, Axa Insurance, said that in the Thames Gateway alone 90% of homes are currently at risk of flooding and that vulnerability is growing. He called on government to work more closely with insurers to encourage “more resilient building standards”.

Yet, scientists agree that flood risk models were “uncertain” and pricing risk accordingly was becoming increasingly difficult. Paul Bates, professor of hydrology for the School of Geographical Sciences at the University of Bristol said: “More work needs to be done on the correlation between rising sea levels and flood risks.” He added: “The correlation between rising sea levels and social economic risk is also too simplistic.

He explained the scientists’ predicament. “I am not sure what is needed from us. If we go through the rigour of taking into account every uncertainty then the model will be uncertain. Would insurers be ready to accept that?”

Donovan’s conclusion brought together the views of the panel. “It is going to take a while to confirm how global climate change is impacting flood risk in the UK. Mitigation will reduce the impact on flood risk, but we must adapt and this will cost. And we need to adapt in the most sustainable way.”

Katy Dowell is senior reporter on Insurance Times.