If there is one thing we Britons should surely be able to cope with, it's the rain. We may be wearily resigned to the apparent inability of the nation that invented the steam engine to run a railroad. We may, perhaps, be persuaded by successive governments that our public services are continually in need of "reform". We may even believe that we can excuse being caught unawares, as last year, by drought. But this damp island, slap in the path of the wet westerlies, is awfully used to getting a drenching.
Yet here we are, after a few days of heavy downpours, bang in the middle of a national crisis. The rains brought transport to a standstill. A whole town is cut off by water from the rest of the world. Hundreds of thousands of people have lost or may lose their water supplies. Hundreds of thousands more face losing electric power. And we are told that the worst is yet to come.
Things have changed - and we have been caught out because we were not prepared ... We have, of course, had severe floods before; the worst killed 2,000 people when the Severn burst its banks in 1606, while an area the size of Kent was inundated across the country in the spring of 1947. But they have become more frequent - more than doubling over the past century.
This is mainly down to the weather. We are used to miserable summers - but this month is expected to be the wettest-ever July, following the wettest-ever June. We have also experienced torrential rains before - in July 1955 an unmatched 10 inches fell in Martinstown, Dorset, in just 24 hours. But these, too, are becoming more common.
Research at Newcastle University last year concluded that downpours have become twice as intense over the past 40 years, and that the worst come four times more often. And the Environment Agency predicts that heavy rainfall will become three or four times more common in coming decades, increasing flooding tenfold.
This is only to be expected as the world heats up, injecting more energy in the climatic system and evaporating more water from the sea. As The Independent reported yesterday, a new scientific paper will tomorrow firmly make the link between heavier rainfall and global warming.
The more precipitous the downpour, the less chance the rain has to be absorbed by the ground and vegetation, and the more likely it is to race down drains and into rivers, making them overflow. We have made this worse by paving over more and more of the countryside for housing, roads - and even driveways and garden patios.
This is the second thing that has changed over the past decades. We have built over a great deal more land. And that has not merely made flooding worse but aggravated its effects, by putting homes right in the way of the rising waters.
Half of all housing built in Britain since the Second World War - covering a total area the size of the West Midlands - has been sited on land prone to flooding. Councils and ministers have constantly disregarded warnings from the Environment Agency about unwise developments. The consequences are plain to see; most of the houses inundated in this summer's floods have been relatively new, erected in the wrong place.
Yet, even now, nearly one in every six new buildings is being placed in flood zones - and present plans suggest that this will rise to almost one in three between 2016 and 2021. The Association of British Insurers wants houses planned for much of the Thames Gateway to have their living areas on the first floor to keep them dry.
To compound the danger, successive governments have neglected Britain's flood defences. A report by the National Audit Office last month concluded that only 57 per cent of them - and just 46 per cent of those most important ones, such as those protecting towns, are in good condition.
Worse, ministers have consistently refused to give the Environment Agency the money it needs to build enough new ones, causing vital schemes to be delayed for years. Last year, they even cut the budget. In the wake of this summer's floods they have increased it by a third; but this won't take effect until 2010 and will still fall far short of what is required.
All these factors mean that the number of British homes at risk of flooding is projected to rise from two million to 3.5 million over coming decades.
Of course, global warming is the most important of these factors. If the climate were not changing, it could be argued that it would be wrong to build costly defences against rare events, and we might have got away with building on flood plains. But the increased flooding that will accompany a warmer world makes a change of course imperative.
Perhaps it is salutary that Gordon Brown should be confronted with a climate-driven crisis so early in his premiership, for he has so far shown little sign that he has fully grasped the importance of global warming. He looked decidedly uncomfortable having to devote most of his first prime ministerial press conference to the floods yesterday. He may care to remember that it was the flooding of New Orleans that first put the skids under President Bush, and to reflect that how he copes with the downpour - and addresses the climate change that brought it - will affect those vital first impressions of his own reign.
Geoffrey Lean is environment editor of The Independent on Sunday