Thames Barrier, London

The Thames Barrier is a flood control structure erected acros the River Thames between 1974 and 1984. It is located at Woolwich, London, and is the world's second largest movable flood barrier, after the one at Oosterscheldekering in the Netherlands. The purpose of the Thames Barrier is to prevent London from being flooded in the event of exceptionally high tide. When it is raised, the water flowing down the Thames is trapped behind it. When it is opened, the water backed up behind it will then be released downriver.

The Thames Barrier was built across a 523 metre span of the Thames. It is divided into four 61-metre and two 31-metre navigable spans, and four smaller non-navigable channels. The flood gates are circular segments operated by rotating. They are raised by hydraulics from a horizontal position on the riverbed to form a steel and concrete barrier when called to action. They can rotate further to allow "underspill" to control the water level upstream. They can be rotated all the way to a 180 degree position for maintenance.

The gates are hollow, and are 40mm thick. They fill with water when submerged, but empty themselves when lifted out. The four central gates are 61 metres long, 10.5 metres high and weigh 3,500 tonnes. In addition, there are four radial gates by the riverbanks which can be lowered.

Before 1990, the barrier gates were only closed once or twice a year. Since 1990, the number of closures have increased to 4 a year, and in 2003, it closed for 14 consecutive tides.

Thames Barrier
Source: https://commons.wikimedia.org/wiki/File:Thames.barrier.2.london.arp.jpg
Author: Arpingstone

List of Modern Architecture in London