The Christmas flood: storm surges in the North Sea

A 1719 engraving of the 1717 Christmas Flood in which and estimated 14,000 people in the Netherlands, Germany and Denmark lost their lives.

Even criminal masterminds support the EU Floods Directive.

Well, the Christmas cake has been iced, the gin has been poured, so it's time to gather round for a tale of festive inundation.

On Christmas night in 1717, a storm surge hit the coast of the Netherlands, Germany and Scandinavia, causing floods that killed nearly 14,000 people and displacing thousands more. Although one of the most deadly flooding disasters of the early modern era, it was by no means unprecedented; for as far back as we have records, thousands of people have been killed in devastating storm surges in the low-lying lands abutting the North Sea.

Storm surges occur when a combination of high winds and high tides interact to cause coastal flooding. The effect of this depends on local coastal topography: in the North Sea surges can be funnelled into the shallow German Bight and the English Channel.

This animation of a from the UK's storm surge model shows high water in red - you can see it travelling down the east coast of the UK and spreading into the German Bight. Source: National Tidal and Sea Level Facility

Historical reconstructions show that floods have been a feature of the region for millenia; however, massive storm surge disasters have been occurred only since the reclaimation of coastal marshes and construction of dikes began in about 1000 CE. The population and wealth of coastal regions rose, drawn by the fertile reclaimed land and the trade generated by ports, making them more vulnerable to floods which were fewer, but of a greater magnitude - a classic example of the levee effect.

Depictions of historical North Sea storm surges often show the horror of the moment the levee breaks. This astonishing painting of St Elizabeth's Day flood in November 1421, which destroyed a number of villages and permanently flooded a large area of farmland in what is now the Netherlands, was painted soon afterwards. I enjoy the phlegmatic cows, I suppose they've seen it all before.

In the aftermath of enormous floods in 1953 and 1962, major infrastructure was constructed to protect vulnerable parts of the North Sea coastline. This is supported by early warning systems: in the UK, a storm surge model run by the National Oceanography Centre provides forecasts two days in advance - plenty of time to close any stray barriers. Using the wind forecast, the model predict the height of the sea, and the projected tide level is subtracted to give the forecast height of the extra surge, normally accurate to about 10 cm (not bad!). Major flooding hasn't happened since - though governments certainly have an eye on how risks might change as sea levels rise.

But for the moment, let's hope that Christmas flood and its successors stay firmly in the past. Merry Christmas, and stay dry!