By Alex Kirby BBC News Online environment correspondent

Half a century after flooding killed more than 300 people in the UK, the risk of a repetition is increasing, experts say.

The 1953 disaster was caused by a combination of a strong storm surge and an unusually high tide.

By the 2080s we expect a 1.5 m storm surge could happen in the North Sea at least once every seven years Sean Clarke, Met Office

Meteorologists say the chances of such a combination occurring again are continuing to increase.

Rising sea levels in much of south-eastern England are predicted to make matters worse.

The floods 50 years ago caused havoc down the eastern coast of England, killing 307 people, forcing the evacuation of 30,000 more, and damaging or destroying 24,000 homes.

	:	1953 Flood Facts
The North Sea's deadly surge

One train on a line in Norfolk collided with a bungalow "travelling on the crest of a wave", and was stuck for six hours.

Climatologists forecast increased risk

The elements caused the problem, as a storm tracked in from west of Ireland, passed over Orkney and then funnelled down the North Sea, driving a deadly mound of water before it.

But human shortcomings made the natural disaster much worse than it would have been today.

In 1953, there were no satellites or computers, nor any single body responsible for flood warnings. Counties in southern England received virtually no warning until it was too late.

And there was no co-ordination between the UK and the Dutch warning system, though both countries faced a common threat (1,800 Dutch lives were lost).

The threat of another 1953 flood is growing steadily, though modern technology should ensure that fewer people would drown. Two factors underlie the increasing risk.

 Click here to hear Canvey Island residents talk about the night of the floods.

Storms to come

The first is a legacy of the last ice age. The south-eastern part of the UK is gradually settling lower into the sea while the north-west rises, the result of the land slowly springing back after the disappearance of the ice-sheet.

Storm surges will happen more often (Image: Environment Agency)

The second factor is another form of sea-level rise, this time induced by climate change. Climatologists say levels around south-eastern England could be somewhere between 26 and 86 centimetres above their present level in 80 years from now.

Climate change is expected to mean more frequent and more severe storms in the UK. And storm surges will inevitably continue to rage down the North Sea.

They occur when a trough of low pressure moves across the Atlantic towards the British Isles.

Fatal funnelling

The sea beneath it rises, creating a "hump" of water which moves eastwards with the depression.

A surge occurs if this mass of water from the deep ocean reaches the shallow southern part of the North Sea.

In recent years, it has been inland floods that have caused havoc

The height of the surge may be increased again by strong northerly winds. If a high surge coincides with a high "spring" tide (they occur twice a month) and reaches the bottleneck of the Straits of Dover, the alarm bells start ringing.

That is just what happened in 1953, when the surge raised sea levels to 1.5-2 metres above their predicted levels.

Sean Clarke, of the UK Met Office, told BBC News Online: "It's like an asteroid strike. It's only a matter of time before the same thing happens again.

Systems reassurance

"But with climate change as an additional factor, surges will happen more often, and the risk is increasing.

"The return period for a 1.5 m surge in the North Sea - the interval over which you'd expect it to happen again at least once - is 120 years at the moment.

"By the 2080s we expect a 1.5 m storm surge could happen in the North Sea at least once every seven years.

"But our warning systems are a lot better than they were then, so loss of life on the scale of 1953 is pretty unlikely."