Snettisham Floods Coast

In September 2006, television news reported

that catastrophic floods like those in 1953 were threatening

to hit north Norfolk again.

-NEWSREADER:

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

according to the Environment Agency.

50 flood sirens across Norfolk were tested this morning.

Volunteer flood wardens, like Dave Bocking,

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

Residents waited anxiously.

With the same high tides predicted as those in 1953,

disaster seemed a very real possibility.

This is a first trial of the high tide warnings.

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

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

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

-Nice to meet you.

-Nice to meet you.

Why was coastal Norfolk on high alert?

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

from the moon and the sun.

But what people were really worried about

was the bit that comes on top.

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

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

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

-That's probably enough.

-Right.

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

-OK.

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

-So you're tipping in North Sea.

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

-It's rising up the other side.

-That's probably enough.

-OK, there it is.

-Excellent.

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

-That's right.

-Suck at this end of the tube.

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

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

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

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

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

Now this corresponds almost exactly to 50 millibars.

A millibar is the unit of air pressure.

-So it's one centimetre per millibar.

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

Now the same effect will happen in the ocean.

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

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

Or conversely, as the air pressure gets higher,

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

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

The weather was good, atmospheric pressure was comparatively high,

pushing the sea level down,

counteracting the effects of the very high tide.

In January 1953, the opposite was true.

A higher than usual tide coincided with low air pressure

due to a deep depression out in the North Sea.

It was the resulting sea level rise,

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

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

It's terrifying, very, very terrifying.

The sea has no friends.

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

A lot of my best friends all got drowned.

29 people got drowned down here.

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

I come down sometimes,

and sit and cry.

I've done that many a time.

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

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

coincide at least once every 250 years.

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

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

Subtitles by Red Bee Media Ltd