The Thames Barrier spans the river at Woolwich Reach, where the river is 520 metres wide. It is an amazing feat of engineering built to control flooding along the River Thames. Construction began in 1972 and took ten years to complete. The barrier is formed from 10 moveable underwater gates, which are supported by large steel half-domes placed across the river.
When the barrier is not in use, the gates are open, allowing the free movement of river traffic. The gates can close in minutes, forming a continuous steel wall that seals off the upper river from the sea.
Over 80 members of staff at the Environment Agency operate the barrier and its associated flood defences. The Barrier Controller makes the decision to close the barrier based on the predicted height of the incoming tides. Dangerous conditions can be forecast up to 36 hours in advance. Ideally, the barrier is closed three to four hours before the peak of the incoming tide reaches the site. This allows time for local shipping to be informed by the Port of London Authority.
The annual cost of operating and maintaining the Thames Barrier is approximately 6 million. Another 5 million is spent on the river embankments and walls.
Since its opening in 1982, the Thames Barrier has been used to protect London from the risk of flooding on more than 80 occasions. In the first 10 years of operation, the Barrier was closed just ten times. In the following 10 years, it was closed 54 times.
It is estimated that by 2040 the Thames Barrier will not be strong enough to hold back the tides. Work is already starting on a project to design a stronger replacement to defend the next generation of Londoners from the sea.
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