Taming the Thames
The Thames Barrier
Rising from the River, the nine silver gate houses of the Thames Barrier seem to form an avant-garde sculpture rather than one of the most important flood barriers in the world. When the gates of the barrier are raised in the defensive position, a wall of steel more than half a kilometre long and twenty metres high stands between the deadly swell of the river and the City of London.
Tides which threaten London
The River Thames, which runs through the centre of London, is a tidal river. A tide is a change in the water level that is actually caused by the gravitational pull of the moon on the water. Every day there are two high tides and two low tides as the moon rotates around the earth. Normally this daily cycle is not a problem, but when certain weather conditions occur in confluence at the correct time in the lunar cycle, a surge tide is created. Surge tides have historically been one of the greatest threats to the City of London.
Taps to turn off the tide
The gate houses of the Barrier can, in a matter of minutes, rotate their protective gates to stop an incoming surge tide from devastating the City; however, there is generally 36 hours warning of a surge tide, and the gates are raised well in advance of the upcoming surge to avoid a dangerous reflection wave that could cause damage downstream. Without the Barrier, the City would be at serious risk. If a surge tide reached Central London today, it could cost the City in excess of ??30 000 m.
Submitted by: A. Wallen, Worcester Polytechnic Institute, 21 January 2007
