Located just downstream of central London at Woolwich, the Thames flood barrier was constructed to protect London from any storm surges the North sea might throw their way along with very high tides. The barrier is the second biggest, with the Oosterscheldekering barrier in the Netherlands holding the record.
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[Image Courtesy of Flickr]
The barrier was erected in 1982 and was constructed in a series of nine steel gates that stretch 520m over the river Thames. There are ten steel pillars 61 meters wide and these are sitting on blocks of concrete that sit on the bed of the river Thames. Each single one of these pillars rises as tall as a five storey building.
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[Image Courtesy of Flickr]
Since it was constructed the barrier is said to have saved the lives of Londoners around 70 times. Flooding has always been one of the issues that London has been faced with. It was said that the earliest noted time of the river rising above the banks of the river Thames was in 1099, the Anglo-Saxon Chronicle reported that the river Thames had “sprung up to such a height and did so much harm as no man remembered that it ever did before.”
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[Image Courtesy of Flickr]
During the 16th century fish were said to have been seen in the grounds of Westminster Hall, in the diary of Samuel Pepys it said “last night the greatest tide that ever was remembered in England to have been in this river, all Whitehall having been drowned.”
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[Image Courtesy of Flickr]
The last time flooding occurred and covered London was during 1953 and at this time 300 people died. Since then the river Thames has risen by 50cm and it is going to continue its rise by around another meter per century.
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[Image Courtesy of Flickr]
When the barrier gates are open they remain flat against the bottom of the river floor and this means that any vessels can pass through, along with the river, as it is allowed to flow. However, when needed the gates can be closed and they do this by rotating up into position so that the flow of the river is stopped.
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[Image Courtesy of Flickr]
The gates are hollow, being constructed of 1.6 inch thickness of steel and weighing 3,200 tonnes. As the gates are hollow they fill up with water from the Thames when they are submerged on the floor and then empty out the water as they rise up.
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[Image Courtesy of Flickr]
Construction work on the Thames barrier started in 1974 and the barrier was openedofficially a decade later. While the barrier had originally been given a lifespan of up to 20130, analysts have now predicted that the barrier could offer adequate protection until 2060 to 2070.
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[Image Courtesy of Flickr]
 Source:http://interestingengineering.com/