When the Thames Barrier was built as an elegant stainless steel-capped bulwark to protect Londoners from flooding in the 1980s, it was designed with additional capacity just in case melting glaciers raised sea levels.
“Climate change was not even in the dictionary,” said Andy Batchelor, 63, the operations manager who started work on the barrier the day it was opened by Queen Elizabeth II on May 8 1984.
Although the barrier was built to last until 2030, the Environment Agency, the public body that runs and maintains it, has since said the infrastructure will protect London until 2070.
Now on its 40th anniversary, there are questions over that strategy as scientists warn that London risks being overwhelmed by sea-level rises, intensifying storms and more flooding.
“It’s a beautiful, big, sexy barrier,” said Hannah Cloke, a professor of hydrology at the University of Reading, adding that the infrastructure had been doing a good job of protecting Londoners right now.
But, she added: “We are walking into a future where we know we’ve got a changing climate, we know we’ve got more rainfall coming . . . It’s definitely not looking the same as it was when the Thames Barrier was designed and built.”
The barrier was designed to protect Londoners from rising sea levels and the north-south tilt, which is gradually sinking the south-east of the country.
According to the EA, it shields the Houses of Parliament, the O2 arena and Tower Bridge from tidal surges, as well as protecting 116 railway and Tube stations, 300km of major roads and £321bn worth of residential homes.
Built on a flood plain, London has always been prone to river overflows. The diarist Samuel Pepys noted that his house was “miserably overflooded” in 1663. But it was a tidal surge in 1953 which killed 300 people that triggered the construction of the barrier.
Since it was built, the gates have been raised more than 221 times, including 50 times in 2013-14 — the busiest season ever. Although a close watch is kept on the weather, the decision to close the gates — “in anger” as Batchelor describes it, using a military term — is usually made about 12 hours in advance.
The number of gate closures is now increasing, with the annual total expected to rise to 30 times by 2030. The repeated closures add more wear and tear to the barrier and prevent maintenance from being done.
“If we do need to close the Thames Barrier more than we thought we did, then it’s going to have a shorter lifespan [of the existing barrier],” said Cloke.
The EA is planning to make a decision on how to bolster the barrier by 2040. Options include raising its height, building a new barrier with locks on the existing site to improve resilience, or a new structure altogether downstream. Another plan is to install “flood storage areas”, reservoirs where surplus water can be diverted.
In the meantime, the EA is developing a 15-year programme to raise the flood walls that line both sides of the Thames river to the east of the barrier through Kent and Essex, by an additional half a metre by 2040. Those in central London will be raised by half a metre before 2050.
Batchelor insisted that the barrier, which is manned 24 hours a day, would continue to protect Londoners. “It’s a sleeping giant that rolls into action when it’s needed,” he said.
He is proud of the carefully designed back-up systems, such as power supplies on both sides of the river, and the predictive maintenance that avoids faults before they happen. The stainless steel caps had never required cleaning, he added.
Designed by the engineer Charles Draper, who was inspired by his gas cooker taps, the barrier’s gates normally lie flat on the floor of the Thames but can be rotated upwards to block the river flow. It takes up to 90 minutes to fully close, starting with the outer gates, which create a steel wall preventing water from flowing upstream.
The barrier has been so successful that people have forgotten the extent of the city’s vulnerability to flooding, according to experts. In the 1970s and 1980s, a shrill siren would warn Londoners when they were at risk, while posters and TV adverts sent instructions on what to do when faced with rising water.
But experts say alarm bells are ringing once again. The London climate resilience review, commissioned by London mayor Sadiq Khan, found that only 9km of the 126km in flood defences west of the Thames barrier were “sufficiently high to last beyond 2050”.
Emma Howard Boyd, former EA chair, who is overseeing the report on London, said: “We need to keep a huge focus on the large infrastructure that needs to be built to continue to protect London.”
The barrier was decades in the planning and took eight years to build at a cost of roughly £535mn in 1982, the equivalent of about £2.6bn today.
The Conservative government cut the budget for flood defences in England and Wales soon after it came into power in 2010. A decade later it announced £5.2bn in spending on flood defences, double the amount spent during 2015-21, though following previous spending cuts. At the time the government said this was designed to protect 336,000 properties by 2027.
Since then it has reduced the number of properties forecast to be protected by 40 per cent to 200,000 properties as a result of cost increases, the National Audit Office said. Any new barrier is expected to cost billions.
“We should be celebrating this barrier,” said Cloke. “It’s done a brilliant job of protecting Londoners from floods. But we have to focus on the future. We need that [new] barrier. We need it sorted out quite soon.”
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