SEVEN years ago it was people living along the Mississippi who saw floods sweeping through their homes. Earlier this year it was Mozambique, then the European Alps and Vietnam. Now it鈥檚 Britain鈥檚 turn to see normally placid rivers in full spate, reclaiming their flood plains from the high streets and car parks and backyards. But what is the cause?
The weather is always unruly. Most weeks, by sheer chance, some kind of weather record is broken somewhere, and now it鈥檚 Britain鈥檚 turn. But there may be more to it than chance. Copies of a report from the UN鈥檚 Intergovernmental Panel on Climate Change now in circulation but not due for official release until May, confirm that during the past century 鈥渢here has been an increase in heavy and extreme precipitation events in the mid and high-latitudes of the northern hemisphere鈥�.
This pattern could have many causes. One is that we are finally beginning to see the effects of man-made climate change. The world is demonstrably getting warmer, and many climate models predict that warming will make winters in northern Europe wetter.
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Just last week, Scenarios for Climate Change for Europe, a study sponsored by the European Union, predicted a 20 per cent increase in the peak flow of the River Thames. The same day newspaper hoardings across London announced a 鈥渇lood alert on the Thames鈥�. That, of course, was pure chance. We can鈥檛 say that global warming has 鈥渃aused鈥� a particular downpour in Britain-or the Alps, Vietnam or Mozambique. Weather is too random for that. But global warming may well be shifting the probability that extreme weather will occur. And probability is crucial in our practical response to climate change.
In England and Wales, the Environment Agency designs barriers to cope with the severest floods expected in a hundred years. This month鈥檚 events will force it to recalculate the odds, just as earlier floods are forcing recalculations elsewhere.
One lesson everyone should have learned is that massive engineering works aren鈥檛 necessarily the answer. The US spent $7 billion over 60 years trying to contain the Mississippi, but that didn鈥檛 stop the floods of 1993. In Britain, the Environment Agency has been warning for years that towns and villagers have made themselves increasingly vulnerable to heavy rain. The water meadows and ploughed fields, lakes and bogs that once soaked up storm waters are losing their capacity to do so (see 鈥淔urrowed fields fend off floods鈥�). The risk of flooding rises every time a farmer plants a field that was formerly left bare over the winter, or a developer concretes a patch of green for a superstore. Or indeed, when flood defences are raised somewhere upstream. Flood defences that cut rivers off from their flood plains just shift the danger elsewhere.
Last weekend, Britain鈥檚 Deputy Prime Minister, John Prescott, promised millions to repel the rising waters. If by this he means laying more concrete, he should talk to his counterparts in the US, who are busy tearing down levees on the Mississippi and giving the river back some of its flood plain. The Germans and the Dutch plan the same on the Rhine.
Rivers need space. If that means changing the way land is farmed or stopping certain kinds of development, so be it. It is too late to halt global warming in its tracks. To deal with the increasingly unpredictable and extreme rainfall it will likely bring, we have to work with nature rather than try to defeat it.
