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It was when the water started coursing through Covent Garden and Pudding Mill’s Docklands Light Railway Stations on July 25 that people began to take out their phones. What they recorded on their cameras looked biblical: torrents of water tearing down steps and submerging ticket barriers.
In all, nine stations on the London Underground were compelled to close by flash flooding caused by heavy rain showers – an intermission in a summer that has been swelteringly hot.
Our weather is getting worse. A report published on July 29 by the Met Office, which monitors the UK’s weather, found that 2020 was the third warmest, fifth wettest and eighth sunniest ever recorded. Rain is a major contributor to our extreme weather events, the Met Office found. Last year, two of the three wettest days ever happened. “Such extreme weather impacts show how vulnerable much of our existing infrastructure is even in cities like London let alone in less well-off countries,” Asad Rehman, a spokesperson for the COP26 Coalition, told the Financial Times.
We’re also causing the problem by developing our cities and shutting off natural flood breaks. “As the city has grown, we’ve concreted or asphalted over most of the land in the city, so there’s less capacity to soak up the rain that comes down,” says Dragan Savic, professor of hydroinformatics at the University of Exeter.
“Instances of heavy rainfall leading to flash flooding are going to become more commonplace due to climate change,” says Helen Jackson, a researcher at Climate Node, a non-profit using data and historical reports to look for examples of climate impact. The Met Office’s report found that the last 30 years in the UK had been six per cent wetter than the 30 that went before it. Yet Jackson is worried that many of those organisations running large infrastructure are prepared for the impact of the climate emergency. “You see that in all areas, from local authorities to people running electric grids and transport systems,” she says. “People are going to get caught out.”
And that includes the London Underground. July’s flooding – which echoed similar issues experienced on the New York subway and a train tunnel in Zhengzhou, China, which killed 12 people by drowning – is just the latest incident of catastrophic flooding that has racked London’s transport systems.
Transport for London (TfL), which runs the Underground, acknowledged but did not respond to multiple phoned and emailed interview requests. The organisation has also repeatedly refused to publish a 2016 report that warned it was “only a matter of time” before the Underground was hit by severe flooding. Some of the highest-risk stations highlighted by the report included King’s Cross, London Bridge, Waterloo, Finsbury Park, Notting Hill Gate, Seven Sisters, Colliers Wood, Stockwell and Marble Arch – many of them centrally-located and integral to the smooth running of the system.
An earlier report, published in 2009 by the Greater London Authority (GLA), found that 72 London Underground and Docklands Light Railway stations are located on floodplains – the majority of which are on the tidal Thames floodplain. A 2018 version of the same GLA report found that 20 stations were susceptible a flood so severe it is expected to happen only once every 100 years, while one-tenth of the entire Underground and DLR network would also be affected by a one in 100 flood event. “Flood water getting into underground stations presents a particular hazard and a major engineering problem if the flood waters were to enter tube tunnels,” the report says.
“London has been fortunate to escape the worst of recent storm events in the UK, but it is only a matter of time before heavy rainfall seriously affects London and the underground network,” TfL’s unpublished 2016 report adds. “The risk is generally expected to increase [as] climate change predictions are that storms will become more intense. There is some evidence to show that these have already increased in frequency.”
According to the report, five times a year ruptured water mains cause flooding on the Tube network, while even holding the water at bay is a full-time task. A 2014 freedom of information (FOI) request to Transport for London revealed 1.4 million cubic metres of water are discharged from the Underground network into London’s sewer system by pumping stations installed across the system. At least 170 pump controller units are installed across the London Underground, gathering data and being remotely operated when needed to alleviate the impact of flooding. And most of the stations situated on the flood plain have had flood doors installed.
Savic says that there are other options to ease the flood risk. “You have structural options and non-structural options,” he says. “Structurally, you raise the entrances. You can even build flood walls and disguise them as a nice set of steps or serpentine entrances where people can go on a bike or a wheelchair.” But that causes issues of speedy access – vital for a network that carries millions of passengers a day. Likewise, automatic gates can be brought in to shut when water levels rise, keeping flooding out of stations, while pumping stations are a solid line of defence. Flood gates have been in place at Waterloo, for instance, since 1939, according to a report in Nature from the time.
It’s self-evident that the changes our climate is going through will have real-world ramifications, says Caroline Russell, a member of the London Assembly, who wrote a 2019 report on the risk of flooding to the UK capital. “Sure enough, when you get a bunch of rain falling on London you get flooded roads, Tube stations and homes, and all the disruption and misery for Londoners they experience from that,” Russell says. The London Assembly member has warned London’s mayor, Sadiq Khan, that more sustainable drainage systems – that funnel off water away from the drainage and sewer system – need to be build to reduce pressure on the sewer system.
As part of her research, Jackson has trawled through thousands of newspaper articles detailing instances of flooding events across London, looking to see whether they had become more commonplace. When it comes to the impact on the London Underground, her belief is that issues are cropping up more often, and with bigger impacts, in recent years. “It’s pretty clear that happens more recently to a greater extent than they did in the 2000s,” she says, even accounting for potential reporting bias.
While the floods of this summer have garnered attention because of their social media virality, Jackson has documented significant flooding incidents on the Tube in 2014, 2017 and 2018. Incidents obviously pre-date this: in 2012 Stratford station was deluged with two million litres of water after a water pipe burst; as the Underground was being built in the late 1800s and early 1900s using a cut-and-cover tunnelling method, heavy rain could easily flood the system.
“2016 was also quite a bad year,” Jackson says, with several incidents of Tube stations being closed due to flooding. The overwhelming majority of incidents Jackson has tracked happen in the summer, with a single instance of Canary Wharf closing in January 2017.
Russell’s own literature review in 2019 showed that 41 different Tube stations had closed due to flooding in the previous five years, with one in three London Underground stations at risk of flooding. Those on the Northern and Central lines were most likely to be at risk. The average closure duration was more than two hours. Russell conducted the review because she was unable to find reputable data about the risk of flooding to the London transport network. “There’s quite a lot of data, but it’s very disparate and it’s not properly organised,” she says. “There’s a real job for the mayor to do to collect everything, bring it together, and set up a climate data resource for London so all this information is properly held.”
There are some indications that’s happening. A 2019 document indicates that the Underground contracted a consultancy to help it identify flood risks and to manage those risks. More than 100 users now have access to a model that allows TfL employees to analyse the flood risks on the Underground network quicker than before. But it’s more about managing risk than removing it, warns Savic. “There is no way we can eliminate the risk of any flooding,” he says. “As humans we accept that; we get into our cars and drive into crazy traffic. We accept and manage risk – and we need to do that with flooding.”
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This article was originally published by WIRED UK
