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frightened passengers stuck in flooded subway cars in Zhengzhou, China. That cascading down stairs to the London Underground. A woman walking in muddy, waist-deep waters To get to the New York City subway platform.

Metro systems around the world are struggling to adapt to the extreme weather conditions brought on by climate change. Many are overwhelmed by designs based on the prospects of another era, and investment in upgrades decrease in passenger numbers brought by the pandemic.

“It’s scary,” said Sarah Kaufman, deputy director of New York University’s Rudin Center for Transportation. “The challenge is how can we prepare for the next storm, which should be 100 years away,” he said, “but it could be tomorrow?”

Public transport plays a critical role in reducing car travel in major cities, thereby curbing emissions from cars that contribute to global warming. If commuters fear the sights of flooded stations and start avoiding subways for private vehicles, transportation experts say this could have significant impacts on urban air pollution and greenhouse gas emissions.

Some networks, like London or New York, were designed and built over a century ago. While a few, like Tokyo’s, have managed to strengthen flood defenses, the crisis in China this week shows that even some of the world’s newest systems (Zhengzhou’s system is not even a decade old) may be overwhelmed.

Robert Puentes, executive director of the Eno Transportation Center, a nonprofit think tank focused on improving transportation policy, said retrofitting subways against flooding was “an enormous undertaking”. But when you compare that to the cost of doing nothing, it starts to make a lot more sense.” “The cost of doing nothing is much more expensive.”

Adie Tomer, Senior Fellow at the Brookings Institution Metropolitan Policy Program, said subways and rail systems are helping to combat the spread and reduce the amount of energy people use. “Metros and fixed rail are part of our climate solution,” he said.

The recent flood is another example of the type of extreme weather that is consistent with the changing climate around the world.

Just days before the Chinese subway nightmare, 160 people died in floods in Germany. Massive heat waves brought misery to Scandinavia, Siberia, and the Pacific Northwest in the United States. Wildfires in the West of the Americas and Canada sent smoke all over the continent last week and triggered health warnings in cities like Toronto, Philadelphia and New York, giving the sun an eerie reddish hue.

Floods have also flooded roads and highways in recent weeks. NS The collapse of part of California Highway 1 Its entry into the Pacific Ocean after heavy rains this year was a reminder of the fragility of the country’s roads.

But more intense flooding poses a particular challenge for aging subway systems in some of the world’s largest cities.

Metropolitan Transportation Authority in New York 2.6 billion dollars invested It has been in resilience projects since Hurricane Sandy flooded the city’s subway system in 2012. Even on a dry day, about 14 million gallons, primarily groundwater, flow through a network of pumps. Still, the flash flooding this month showed that the system remained vulnerable.

“Trying to work within the constraints of a city with aging infrastructure and an economy recovering from a pandemic is tough,” said Vincent Lee, vice president and technical director for water at Arup, an engineering firm that has helped renovate eight subway stations. Other facilities in New York after the 2012 storm.

London’s sprawling Underground is facing similar challenges.

“Most of London’s drainage system is Victorian,” said Bob Ward, policy director at the Grantham Institute for Climate Change and Environment Research in London. And this has a direct impact on the city’s Underground system. “It is not currently capable of coping with the increase in heavy rainfall we are experiencing as a result of climate change.”

Meanwhile, the crisis in China this week shows that even some of the world’s newest systems may be overwhelmed. As Robert E. Paaswell, professor of civil engineering at the City College of New York, said: “The subways will be flooded. Because they are underground, they will be submerged.”

To help understand how underground flooding works, Taisuke Ishigaki, a researcher in the Department of Civil Engineering at Kansai University in Osaka, Japan, built a diorama of a city with a bustling subway system, which then unleashed the equivalent of about 11 inches of rain. in a single day.

Within minutes, floodwaters pierced several subway entrances and began gushing down the stairs. After just 15 minutes, the diorama platform was 8 feet underwater – a series of events led by Dr. Dismayed to see Ishigaki appear in real life in Zhengzhou this week. There, the floodwaters quickly drowned the passengers still standing in the subway cars. At least 25 people lost their lives in and around the city, 12 of them in the subway.

Dr. Ishigaki’s research now informs a flood monitoring system used by Osaka’s expanding underground network, where special cameras monitor surface flooding during heavy rainfall. Passengers are immediately evacuated underground via other exits, while water above a certain hazard level activates emergency protocols where the most vulnerable entrances are sealed (some can be closed in less than a minute).

Japan has made other investments in flood infrastructure, for example cavernous underground cisterns and flood gates at subway entrances. Last year, private rail operator Tokyu, with support from the Japanese government, completed a massive cistern to capture and divert up to 4,000 tons of floodwater at Shibuya station, a major hub in Tokyo.

Still, if there is a major breach in many rivers that run through Japanese cities, “even these defenses won’t be enough,” said Dr. Ishigaki

Public transport advocates in the United States are calling for the use of pandemic relief funds for public transport. “The scale of the problems has become larger than our cities and states can handle,” said Betsy Plum, executive director of Riders Alliance, an advocacy group for subway and bus drivers.

Some experts suggest another approach. With more extreme flooding, it will always be impossible to protect the subways, they say.

Instead, investment needs to be made in bus and bike lanes that can serve as alternative means of public transport when subways are flooded. Natural defenses can also provide relief. Rotterdam in the Netherlands has grown plants along its tramways that allow rainwater to be absorbed by the soil and reduce heat.

“During the pandemic, you’ve seen how people get around on their bikes, the most resilient, least disruptive, low-cost, low-carbon mode of transportation,” said Anjali Mahendra, research director at the World Resources Institute Ross Center for Sustainable Cities. Washington-based think tank. “We really need to do a lot more to connect parts of cities and neighborhoods with these bike corridors that can be used to get around.”

Some experts question why public transport should be underground in the first place and say that public transport should take back the street. Street-level light rail, bus systems and bike lanes are not only less prone to flooding, but are also cheaper to build and easier to access, said researcher Bernardo Baranda Sepúlveda of the Mexico City-based Institute for Transport Development. transportation nonprofit.

“We have this inertia from the last century, to give cars most of the available space above ground,” he said. “But a bus lane carries more people than a three-lane car.”