AS PEOPLE all the way from Germany to the Black Sea begin cleaning up the devastation caused by some of Europe’s worst ever flooding, questions are being asked about why the floods were so bad, and who – or what – was responsible.
There is fresh evidence linking the floods to global warming. The warmest ever summer in the northern hemisphere has fed exceptional amounts of moisture into rain systems forming over the Atlantic. Also, the rapid melting of Alpine glaciers has added to the unprecedented rush of water down some of the continent’s largest rivers. But it is the widespread building that has taken place on river flood plains across central Europe in recent years that is to blame for why the intense rainfall had such a catastrophic effect.
The rains were worst over a zone stretching from the Austrian Alps into the Czech Republic. Parts of the Czech Republic had four times their normal rainfall for August in only 36 hours. And there is no doubt that unusual weather was the prime cause: rain-carrying cyclones that normally pass over northern Europe in summer instead tracked south and dumped their rain over the Alps.
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Meteorologists say they can find nothing to link this shift in the cyclones’ path to global warming. But it is clear that their more southerly track, coupled with high temperatures over the North Atlantic this summer, caused more evaporation from the ocean and helped to form particularly heavy storm clouds. This led to rainfall of an almost tropical intensity.
Glaciologists say that events in the mountains, where most of the rain fell, made matters worse. Towards the end of summer, mountain rivers are already swollen by meltwater from glaciers. And global warming has increased this flow, says David Collins, a glaciologist at the University of Salford. There are no confirmed figures yet, but it seems that Alpine glaciers released more meltwater this summer than ever before. The rains came on top of that.
Equally significant, the timing of the rains meant that many mountains had virtually no capacity to absorb water. With most of the winter snows melted by August, mountainsides were covered in bare ice. The rain ran off the mountains as if they were covered in concrete, says Andy Barrett, a glacier specialist at the University of Colorado.
Individual governments cannot do much about such factors. However, they could manage the rivers and flood plains within their borders to minimise the damage caused by heavy river flows. Yet there is growing evidence that policies over recent years have, if anything, made matters worse.
Engineers have channelled all the major rivers that flooded this month – draining wetlands, straightening meanders and cutting them off from their flood plains with high banks. The aim was to protect surrounding land from floods and send the water down to the sea as fast as possible. But instead it has tended to create massive and comparatively sudden surges of water down the rivers, where in the past the water would have been delayed for days or even weeks as it meandered across the river’s natural flood plain.
“Flood peaks are higher and more damaging in places where wetlands and flood plains have been cut off from rivers, channelling more water into an unnaturally small space,” says Günther Lutschinger, a flood-plain ecologist and chief executive of the environment group WWF Austria. Four out of five wetlands on the flood plain of the River Danube – Europe’s second largest river and one of the worst affected during the floods – have been drained in recent years. And mountains have lost most of their forests, severely reducing their capacity to absorb heavy rains.
Newspapers in Austria and the Czech Republic last week began to blame the floods on the “greedy mayors” of towns and villages in mountain valleys, who have chopped down forests and built holiday homes on the banks of rivers. But this is not just about the tourist industry. Up to 10 per cent of Europeans live or work on the flood plains, and in Hungary, that figure is 25 per cent.
That’s one reason why, nine times in the past five years, there have been mass evacuations, numerous deaths and extensive damage as a result of river floods in central Europe, with costs running into tens of billions of euros. “The Danube has had two once-in-a-century floods in the past 11 years, and three in the past 50,” says Lutschinger.
Rob Leuven, an environmental engineer at the University of Nijmegen in the Netherlands, says engineers on the Rhine learned their lesson after massive floods in 1997. “Government policy is now to allow rivers to take more physical space,” he says. Rivers are being allowed back onto their flood plains, and overspill areas of low-lying land called “calamity polders” have been created beside them to lessen the impact of major floods.
But away from the Rhine, the lessons of recent years have still not been learned. A similar plan for the Elbe around the German town of Magdeburg, likely to be one of those worst hit by the floods, has yet to implemented. And Lutschinger’s calls to open up 800 square kilometres of new flood-retention areas in Austria have gone unanswered. “We hope the government will do this now,” he says. “It would be a much better investment than trying to make the dykes higher.”
