|The Thames Barrier|
|The thumbnails below are linked to larger pictures
The Thames Barrier can be reached by road, or river boat from Westminster or Greenwich. If you wish to view the barrier visitors centre then the road option is necessary, as the boat is normally a round trip.
The barrier is an impressive construction and is the worlds largest movable flood barrier, spanning 520 metres across the Thames at Woolwich. The barrier completed in 1982, is valued at over £1000 million and took 8 years to build
The barrier was designed to protect the capital from flooding until the year 2030, although whether global warming will invalidate the original calculations remains to be seen. It was the results of the 1953 floods in which 300 people were drowned and 160,000 acres of farmland flooded, that finally prompted an urgent enquiry into solving the threat. The design was selected from 41 proposals and succeeded because it minimises interference with the natural flow of the river, does not restrict headroom for shipping, and is aesthetically pleasing.
The four main gates comprising the barrier are each as high as a five storey building and as wide as the as the opening of Tower Bridge (61 metres). Each gate is operated by its own electrically powered 'hydraulic power packs', which are housed immediately below the stainless steel roofs. When fully open the semicircular gates are set flush into the river bed in concrete supporting sills, so as not to provide an obstruction. They can also be raised clear of the water for maintenance purposes. The various operational positions of the gates are illustrated by the diagrams below (this links to larger drawings).
Since its completion the barrier has been raised over 64 times as a precaution against flooding, they are also raised monthly for a test period at low tide.
The barrier is worth a visit just to appreciate the enormity of the project and to admire the good engineering design. You also get a good view of the millennium dome from the river, which is perhaps an example of a less practical design.