Severe winter floods forced London’s Thames Barrier to shut for a record 20th time in 10 days on Monday, pushing the vast structure protecting the centre of the British capital close to its recommended number of annual closures.
The latest closing of the giant steel gates that span the Thames – mostly done to protect what authorities describe as “several tens” of riverside properties west of London – mean the barrier has closed 40 times this year.
The barrier should close a maximum of 50 times a year, according to its operator the Environment Agency, because the risk of it failing rises the more it is shut, and frequent closures affect maintenance work.
So far, the agency says the unprecedented number of consecutive closures – each costing £5,000 – are not a problem for the barrier, located near Woolwich in the capital’s east.
“We are operating it because we can, to protect perhaps several tens of homes in the west of London,” said David Bedlington, flood risk manager at the agency, emphasising central London was safe.
“It is really important to get across that there is no risk to London as a whole,” he said, explaining the properties upstream that were being shielded by the closures were largely around Ham Island, Old Windsor, and Trowlock Island at Teddington.
These areas have already suffered as a result of the relentless rainfall that has seen the Thames rise to its highest levels in more than 60 years in some areas.
The Thames Barrier was originally designed to protect central London from sea flooding and was closed twice in December when fierce gales led to a serious storm surge and the highest tides in 60 years along parts of English east coast.
However, it can also help regulate river flooding. It has been used this winter to create a reservoir for the huge volumes of water from the swollen Thames that would otherwise cause even more damage to properties upstream.
The Environment Agency has long said the effectiveness of its flood defences depend on the extent to which sea levels rise as a result of climate change. But it currently expects the Thames Barrier to protect London until at least 2070.
The number of closures has been rising steadily over the barrier’s lifetime, however, from just four times in the 1980s and 35 times in the 1990s, to more than 100 times since 2000. This year’s 40 closures already equate to nearly a quarter of the total number of times the barrier has been shut since it was completed in 1982.
Depending on how much it needs to be used in future for its primary purpose of protecting London against sea flooding, it may no longer be possible to use it to shield properties upstream from river inundation.
“We are using the barrier to protect properties from river flooding and we will continue to do that for as long as we can,” said the Environment Agency’s Mr Bedlington.
“If we have to shut it down more frequently for tidal flooding, we will have to review the whole operation but we are not at that point yet.”
Other hydrology experts say the unprecedented number of consecutive barrier closures this year should not necessarily be a cause for alarm.
“It is quite something,” said Professor Andrew Wade from the University of Reading. “But it is just an exceptional year this year because of all rainfall we are getting.”
He added: “Next year we might see no closures whatsoever. This is just a spike, I think. The thing to do is to see if the spike turns into a trend. Only time will tell.”
The barrier was built after disastrous floods around the east coast of England and Thames Estuary in 1953 that led to the deaths of more than 300 people.
Authorities realised that damage would have been even worse if the flooding had reached the densely populated capital, prompting the construction of the barrier for more than £535m, or well over £1bn at current prices.
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