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Can building snowmen really help to prevent flooding?

2013-01-25 05:49:58

As government directives go, advising people to build a snowman to help prevent flooding is among the more bizarre.

An Environment Agency spokesman has been widely quoted as suggesting snowmen could help stop floods by slowing down thawing.

The agency has since qualified its comments, saying that it is unlikely to make much difference.

But experts say that, as strange as it may sound, there is some truth behind the suggestion.

'Makes some sense'

Dr Sim Reaney, lecturer in physical geography at the University of Durham, said: "On a very practical level, it does actually make some sense.

"I've read through some of the stuff myself. The more you pile up snow, the longer it takes to melt.


"It was an interesting headline but there is some science behind it. I can see how it would work.

"Rain on snow is a big cause of flood events. Any snow that is compacted takes longer to thaw, whether it be on a road or as a snowman."

'White terracotta army'

Dr Reaney said that in urban areas, where melted snow runs directly off roads and pavements into drains, snowmen would make more of a difference than in fields where it would take longer for the water to filter into watercourses.

"You are making a difference," he said.

"It is action at a sensitive place in the landscape. You are doing something where it needs to happen."

But Dr Reaney was sceptical that snowmen could have a major impact on the rate of thaw.

"If everybody made a snowman, it doesn't actually take up that much snow," he said.

"The country is covered from top to bottom."

Weather forecaster Jim Bacon of WeatherQuest, based at the University of East Anglia (UEA) in Norwich, agreed.

"If you look at the masses of fields we have, you'd probably need a white terracotta army," he said.

But Mr Bacon said the underlying theory behind the suggestion was sound.

"Snow is melting all the time from the warmth of the ground underneath it, and the warmth of the air moving over it," he said.

"If you roll it up into a ball, you're decreasing the surface area and that would slow down the rate of melting."

'60 million snowmen'

The flaw in the theory, he said, was the time lag between the snow melting and the water reaching rivers.


"A lot of the time when you get flooding, it's due to the slow accumulation of water. It takes a while for water to filter through the ground and into the rivers.

"It might well be that the rate of melt from snowmen coincides with the water going into the rivers over a longer time frame so it wouldn't help."

Professor Kevin Hiscock, an expert in hydrology at UEA, said: "You'd need, say, 10 sq metres (107 sq ft) of snow to make a snowman.

"The catchment area of the River Wensum in Norfolk is 600 sq km (231 sq miles), so that's the equivalent of 60 million snowmen."

So what can you do? The latest advice from the Environment Agency is perhaps more sensible, if not quite as much fun.

"The most important thing anyone can do to protect themselves from flooding is to check out if they are in a flood risk area, and sign up to free flood warnings on the Environment Agency website," said a spokesman.

Source: bbc.co.uk

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