14 October 2021

London is getting wetter – and its transport network may be too slow to adapt

Climate science shows extreme rainfall goes hand in hand with a warming world, but the UK’s capital is not getting to grips with flooding.

By Emma Haslett

A London taxi drives through water on a flooded road in Nine Elms, London in July. (Photo by Justin Tallis / AFP)

Even by London standards, 2021 has been wet. Tuesday 5 October saw the latest in a series of downpours that have closed parts of the transport network across the city. This time it was passengers travelling on the Circle and District underground lines who were stranded after Gloucester Road station, to the west of London, was partially closed due to flooding when 26 millimetres of rain fell in a couple of hours.

The closure came after two notable incidents this summer. On 25 July, mobile phone footage showed water cascading into Pudding Mill Lane station in East London as 12 Tube stations closed and cars became stranded on roads. Two weeks earlier, a similar downpour had led to shops and cafes in the tourist hotspot of Portobello Road, not far from Gloucester Road, being submerged under several inches of water on the city’s wettest day in 40 years.

It wasn’t just London that had a wet summer. Weeks after the incident at Pudding Mill Lane, videos circulated of water gushing on to the tracks of a New York subway station as Hurricane Ida battered the city. In July, 12 people died on an underground train in the Chinese city of Zhengzhou as other commuters were filmed just keeping their heads above the water after days of rain. And it’s getting wetter: a Met Office report published this year revealed that 2020 was the UK’s fifth wettest year since 1862, while six of the ten wettest years since 1862 have occurred since 1998.

Such changes are not coincidental, but the direct result of a heating world. The most recent report from the Intergovernmental Panel on Climate Change shows how climate change is intensifying the water cycle, bringing more intense rainfall and associated flooding to certain parts of the world.

Studies have been warning of the risk to London’s transport system for years. A 2016 inquiry commissioned by London Underground found 57 Tube stations are at “high risk” of flooding; it is “only a matter of time” before the network is affected – with “high safety consequences”. Meanwhile, a 2019 report by Caroline Russell of the City Hall Greens warned that surface water is “now seen [as] the most critical flood risk to London”.

London’s response to the risk of floods is complicated further by the funding crisis faced by Transport for London (TfL), the organisation charged with running the city’s transport network, since the beginning of the pandemic. Its income dropped precipitously when lockdown was introduced. In 2020, the organisation came hours from running out of money and was forced to take a last-minute bailout from the Department for Transport. A further agreement followed in June this year.

In its annual report in July, TfL wrote that although climate change adaptation is a “priority”, its data collection and monitoring systems don’t allow for “comprehensive assessments of the impact of current weather events on our operations… Given funding constraints, this is likely to remain a challenge over the medium term”. Lilli Matson, chief safety, health and environment officer of TfL said the organisation is “subject to existing funding deals” that will need to be renewed. “But we’ve made very clear that safety is our first and absolute priority in those discussions.”

This summer’s flooding incidents proved that TfL is equipped to deal with them, added Matson. It works closely with the Met Office to anticipate extreme weather events, and uses cameras sited throughout its network to alert other agencies, including the fire brigade and Thames Water, when necessary.

Snigdha Garg, senior manager of adaptation research and integration at the NGO C40 Cities, said a key part of cities’ prevention strategies is accepting that downpours will happen and managing where the water goes. “We will have flooding,” explained Garg. “We have to build systems that can learn to work around that water, we have to learn to live with that water.” As a first defence, TfL deploys a fleet of “gulley suckers”, which clear storm drains at surface level as soon as a downpour takes place, said Matson.

Longer term, it is counting on the £4bn Thames Tideway Tunnel, better known as the “super sewer”, one of London’s biggest infrastructure projects of modern times. “Thames Water owns all the sewers, and is responsible for that kind of capacity. And [flooding] is very much what the Thames Tideway Tunnel is aimed at,” said Matson.

TfL is also working with developers and planning authorities to ensure there are porous areas where water can be absorbed, known as sustainable drainage systems (SuDS), built into urban spaces. According to its guidance, written in 2016, SuDS can take the form of green spaces, street trees or “permeable paving”, where gravel is pushed between paving stones.

But although that guidance is being used – it is “embedded in the TfL psyche”, said Stephen O’Malley, founding director of Civic Engineers, who worked with TfL on its SuDS guidance – getting the funding to make them commonplace is more difficult. “As you can imagine, trying to secure funding, trying to deliver these features across the landscapes of London is pretty challenging,” he continued. In a separate email conversation O’Malley added: “The rollout of SuDS should definitely be happening faster.”

It’s only a matter of time before London’s capacity to deal with floodwater is properly tested. In 2011, Copenhagen experienced a “cloudburst event” where 15 centimetres of rain fell on the city in less than three hours, causing DKr6bn (£680m) of damage. By 2015, the Danish capital had established a cloudburst plan, which included an expanded sewer network, as well as 300 surface solutions including stormwater roads and playing fields that operate as water detention pools during heavy rainfall. By contrast, London has been slower to adapt to the changing climate.

And it’s not just passengers who are concerned. “Does it worry me?” asked Matson. “Yes. It does worry me a lot. I looked at those videos and it made me feel kind of queasy.”