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Floods and Storms
Floods
Floods can be deadly - particularly when they arrive without warning. Since 1998, more than 30 people have died as a direct
result of flooding in Britain alone. Actually, it takes less rain than you'd think to cloud your day.
A mere four inches of water will ruin your carpet. Six inches of fast flowing water can knock you off your feet, and two feet of
flood water will float your car. But where does it all come from?
Though Britain is no stranger to bad weather at any time of the year, autumn is the classic time for storms.
This is the time of the year when the two factors that influence our weather are most likely to
clash. Warm ocean currents drift up from the Gulf of Mexico, and cold air is coming down from
the Arctic. When these opposing temperatures converge, it can create enormous problems.
The Arctic
Stormy weather
Low pressure develops on the boundary of warm and cold air - this is known to meteorologists as a 'weather front'. The air here
has a natural tendency to rise, and as air rises, it cools. Any water vapour present in the air condenses to form clouds.
Consequently, low pressure is generally associated with wet and windy weather.
Low pressure systems have a habit of queuing up over the north Atlantic. Like buses, sometimes one doesn't appear for ages,
and then three or more come at once. That happened relentlessly in the UK between September and November 2000.
How floods happen
When rain starts to fall, it drains down from the hillsides into streams, along rivers and out into the sea. That's under normal
circumstances anyway. But when rain pours for weeks at a time, the land becomes saturated and Britain's natural drainage
system is likely to fail.
The upper reaches of rivers quickly fill and force the excess water downstream. In the lower reaches, water flows slower. Here,
the river swells and begins to break its banks. This is entirely normal - flood plains are part of the river's natural defence
mechanism.
These low-lying, wide flat areas in the lower reaches of a river provide relief and take up the excess water. It's best not to build
on them, though sometimes people do.
All kinds of debris gets caught up in a flood - dead cattle, sheep, trees, gravel. If any of this
flotsam gets lodged under a bridge, it creates a dam and backs up the whole system. Once that
happens, there are no more chances... unless local residents are insured.