Frightened passengers trapped in flooded subway cars in Zhengzhou, China. Water step down stairs in the London Underground. A woman walks through muddy, waist-deep water to reach a New York City subway platform.
Subway systems around the world are struggling to adapt to the era of extreme weather brought on by climate change. Their designs, many based on the expectations of another era, are being overwhelmed, and investment in upgrades could be squeezed out by the decline in ridership brought on by the pandemic.
“It’s scary,” said Sarah Kaufman, associate director of the Rudin Center for Transportation at New York University. “The challenge is how can we prepare for the next storm, which should have been 100 years away,” she said, “but could it be tomorrow?”
Public transport plays an important role in reducing travel by car in large cities, thus curbing emissions from automobiles that contribute to global warming. If commuters panic over images of submerged stations and start turning away from the subway for private cars, transportation experts say it could have major implications for urban air pollution and greenhouse gas emissions.
Some networks, such as London or New York, were designed and built more than a century ago. While some, like Tokyo, have managed to fend off their floods, the crisis in China this week shows that even some of the world’s newest systems (Zhengzhou’s system isn’t even a decade old) could be overwhelmed.
Rebuilding subways against flooding is “a huge undertaking”, said Robert Puentes, chief executive of the Eno Center for Transportation, a non-profit think tank with a focus on reforming transportation policy. “But when you compare it to the cost of doing nothing, it starts to make a lot more sense,” he said. “The cost of doing nothing is much more expensive.”
Subway and rail systems help fight sprawl and reduce the amount of energy people use, said Eddie Tomar, senior fellow in the Brookings Institution’s Metropolitan Policy Program. “Subways and fixed rail are part of our climate solution,” he said.
The recent floods are another example of the kind of extreme weather that has been consistent with the changing climate around the world.
Days before the nightmare of the China Metro, floods in Germany killed nearly 160 people. Major heat waves have brought misery to the United States in Scandinavia, Siberia and the Pacific Northwest. Wildfires in the American West and Canada sent smoke across the continent last week and triggered health alerts in cities such as Toronto, Philadelphia and New York City, causing the sun to turn an eerie red.
The flash floods in recent weeks have also inundated roads and highways. The fall of a section of California’s Highway 1 into the Pacific Ocean after heavy rain this year is a reminder of the fragility of the country’s roads.
But more intense flooding poses a particular challenge to older metro systems in some of the world’s largest cities.
In New York, the Metropolitan Transportation Authority has invested $2.6 billion in resilience projects since Hurricane Sandy battered the city’s subway system in 2012 against flooding, including strengthening 3,500 subway vents, stairs and lift shafts. Even on a dry day, a network of pumps pumps about 14 million gallons, mainly groundwater, out of the system. Still, this month’s flash floods showed that the system remained vulnerable.
Vincent Lee, associate principal and technical director of water for Arup, an engineering firm that helped upgrade eight metro stations, said, “It is a challenge to work within the constraints of a city with aging infrastructure. Attempts are being made.” and other facilities in New York after the 2012 hurricane.
London’s giant Underground is facing similar challenges.
“A lot of London’s drainage system dates back to the Victorian era,” said Bob Ward, policy director at the Grantham Research Institute on Climate Change and the Environment in London. And this has a direct impact on the underground system of the city. “It has not been able to cope with the increase in heavy rainfall at this time that we are experiencing as a result of climate change.”
Meanwhile, the crisis in China this week suggests that even some of the world’s newest systems may be overwhelmed. As Robert E. Paswell, a professor of civil engineering at the City College of New York, put it: “Subways are about to flood. They are going into the flood because they are under the ground.”
To help understand how underground flooding works, Taisuke Ishigaki, a researcher in the Department of Civil Engineering at Kansai University in Osaka, Japan, created the diorama of a city with a bustling subway system, then covered with about 11 inches of rain. A deluge spread evenly. in a single day.
Within minutes, flood waters breached several entrances to the metro and started falling down the stairs. Exactly 15 minutes later, the diorama’s stage was 8 feet under water – a sequence of events with Dr. Ishigaki was horrified to appear in real life in Zhengzhou this week. There, flood waters swiftly overwhelmed commuters parked in subway cars. At least 25 people died in and around the city, including 12 in the metro.
Dr. Ishigaki’s research informs a flood monitoring system now in use by Osaka’s vast underground network, where special cameras monitor underground flooding during heavy rainfall. Water above a certain danger level activates emergency protocols, where the most vulnerable entrances are sealed off (some can be closed in less than a minute) while passengers are forced through other exits. from underground is immediately extracted.
Japan has made other investments in its flooding infrastructure, such as underground pools and flood gates at subway entrances. Last year, private rail operator Tokyo, with support from the Japanese government, completed a massive cistern at Shibuya Station in Tokyo, a major hub, to capture and divert 4,000 tons of floodwater flows.
Still, if there is a major breach of many of the rivers that flow through Japanese cities, “even these defenses will not be enough,” Dr. Ishigaki said.
Mass transit advocates in the United States are calling for pandemic relief funds to be put toward public transportation. “The scale of the problems is bigger than in our cities and states,” said Betsy Plum, executive director of the Riders Alliance, an advocacy group for subway and bus riders.
Some experts suggest another method. They say that with more extreme flooding down the line, it would be impossible to protect the subway at all times.
Instead, there is a need for investment in buses and bike lanes that can serve as alternative means of public transportation when subways are flooded. Natural defenses can also provide relief. Rotterdam, in the Netherlands, has grown plants along its tramways, which allow rainwater to be absorbed by the soil, and to reduce heat.
Anjali Mahendra, director of research at the World Resources Institute’s Ross Center for Sustainable Cities, said, “During the pandemic, the way people get around on their bicycles is the most flexible, least disruptive, low cost, low carbon mode. ” A Washington-based think tank. “We really need to do a lot more to connect parts of cities and neighborhoods with these cycle corridors that can be used to get around.”
Some experts question why public transport needs to be underground in the first place and say that public transport should reclaim the road. Street-level light rail, bus systems and cycle lanes are not only less exposed to flooding, they are also cheaper to build and easier to use, said Bernardo Baranda Sepulveda, a Mexico City-based researcher at the Institute for Transport Development. Transportation non-profit.
“We have this inertia from the last century to give cars the space available above ground,” he said. “But one bus lane carries more people than three-lane cars.”