Thames Barrier

The part of the Thames River that runs through London is a tidal estuary, and the water levels can change dramatically with the tides.  Historically, these changes could be so severe that they could cause severe catastrophes within the United Kingdom’s capital.  Records of flooding go back to the period after the Norman Conquest, and noted diarist Samuel Pepys recorded an event in 1663 in which Whitehall (the location that then and now contains many governmental offices) was completely flooded.  In more recent years, the 1928 Flood, which was caused by a combination of excess precipitation and an extremely high tide, was notable for killing 14 people and damaging 2000 homes, mainly in South London, and another severe tidal surge in 1953 forced thousands of people in London’s East End to leave their homes. 

The general approach to constructing flood defenses in London has been to simply build larger walls along the riverbank.  However, to protect against the most extreme possible flooding events, the walls would need to be so high that they would potentially block views of the river itself.  Therefore, the UK government decided in the 1970s to build the Thames Barrier to protect against severe tidal surges, with construction starting in 1974 and reaching completion in 1984.

The barrier spans a 520 m part of the Thames River between Silvertown and Woolwich, which is east of and downstream of the center of London but still within Greater London.  The barrier consists of a series of metal-clad structures on piers with gates between them.  Most of the time, the gates are in the down position and sit near the bottom of the river, permitting the river as well as boats to pass through the barrier.  However, when very high tidal surges are forecast for the river or when the barriers are simply being tested, the gates can rotate 90 degrees to form a wall that is several stories tall.

Since the barrier first started operating in 1983, it has been used over 200 times to protect the city from flooding.  Most notably, the barrier was closed more than 50 times over a 13 week period during the particularly stormy winter of 2013-2014.  With the increasing threat of rising sea levels from global warming, the Thames Barrier will continue to play an important role in protecting London from severe flooding.