Snettisham Floods Coast


Snettisham Floods

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In September 2006, television news reported

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that catastrophic floods like those in 1953 were threatening

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to hit north Norfolk again.

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-NEWSREADER:

-Parts of the Norfolk coast are at particularly high risk of flooding,

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according to the Environment Agency.

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50 flood sirens across Norfolk were tested this morning.

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Volunteer flood wardens, like Dave Bocking,

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were mobilised on the days between the 6th and the 13th of September.

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Residents waited anxiously.

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With the same high tides predicted as those in 1953,

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disaster seemed a very real possibility.

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This is a first trial of the high tide warnings.

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It looks as though we're going to get away with it.

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To investigate why this coast didn't suffer the catastrophic floods that many had predicted,

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tidal expert Philip Woodworth has brought some high-tech equipment from his lab.

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-Nice to meet you.

-Nice to meet you.

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Why was coastal Norfolk on high alert?

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It was on a high alert because there was a predicted high tide

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from the moon and the sun.

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But what people were really worried about

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was the bit that comes on top.

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That's due to the weather, and that's the bit which cannot be predicted a long time in advance.

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Philip's promised me that a bucket, a hosepipe and some water

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are enough to show the dramatic effect of weather on sea level.

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-That's probably enough.

-Right.

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-So if you can put your foot on the tube there, Nick.

-OK.

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And we'll invent the manometer, or water barometer.

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-So you're tipping in North Sea.

-I'm tipping in part of the North Sea.

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-It's rising up the other side.

-That's probably enough.

-OK, there it is.

-Excellent.

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-So the water's at the same height in both sides of the tube.

-That's right.

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-Suck at this end of the tube.

-What will that be representing, by sucking into that?

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That will reduce the pressure in this part of the tube.

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And if you can put your thumb over the end when you feel ready.

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OK, excellent. We have here a difference in the water level here,

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in this part of the tube down to here, of a good 50 centimetres.

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Now this corresponds almost exactly to 50 millibars.

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A millibar is the unit of air pressure.

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-So it's one centimetre per millibar.

-It's an accident of units, almost. An easy thing to remember.

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Now the same effect will happen in the ocean.

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And as the air pressure drops, as it does during storms in the winter,

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the air pressure alone will cause the sea level to rise.

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Or conversely, as the air pressure gets higher,

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that will lower the sea level because it pushes it somewhere else.

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And that's exactly what happened to prevent the predicted floods of 2006.

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The weather was good, atmospheric pressure was comparatively high,

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pushing the sea level down,

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counteracting the effects of the very high tide.

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In January 1953, the opposite was true.

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A higher than usual tide coincided with low air pressure

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due to a deep depression out in the North Sea.

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It was the resulting sea level rise,

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combined with storm-force onshore winds, which caused the flooding disaster.

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Dave Bocking was 18 years old when the flood hit his village, Snettisham.

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It's terrifying, very, very terrifying.

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The sea has no friends.

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You know, it will take whatever's in its path.

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A lot of my best friends all got drowned.

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29 people got drowned down here.

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This was why I became a flood warden, because I had seen it before.

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I come down sometimes,

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and sit and cry.

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I've done that many a time.

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For the time being, the flood warning sirens stay silent.

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But meteorologists predict that a high tide and a low-pressure weather system

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coincide at least once every 250 years.

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It's clear that this land is borrowed from the sea.

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One day soon, she may be back to claim it.

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Subtitles by Red Bee Media Ltd

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