Paris Buried a River 100 Years Ago. Now The City Needs To Resurface It to Combat Climate Change
A writer was hired by a French newspaper in 1899. Le Figaro surveyed the damage Parisians had done to the Bièvre, a river that for hundreds of years had snaked up through southern Paris, joining the Seine near the Jardin des Plantes. “It flows slowly, oily and black, streaked with acids, dotted with soapy and putrid pustules,” the writer observed. “In the sparse and sordid grass, peeled like the back of a worn-out horse, parasitic plants grow in abundance.”
The waterway, averaging 13 ft. in width, had featured in Renaissance poetry by François Rabelais and in Victor Hugo’s Les Misérables. But as the Industrial Revolution took off, masses of tanneries, dyers and laundries used and abused the Bièvre’s waters, leaving it resembling an open-air sewer, which authorities decided to pave over. “Tomorrow,” Le Figaro mourned as the 20th century approached, “this once ‘beautiful river’ … will be walled up and bewitched like a sorceress during the middle ages, and in this strange and desolate valley … a new district of tall and flaming buildings will rise.”
Paris’ last stretch of the Bièvre was sealed up in 1912. Many heritage campaigns have been launched to open the river since then because of a strong cultural connection. But, none of these efforts have been successful. Its waters now run beneath the city because they were cut at towns 13 miles from its source.
Today, though, the Bièvre has an unlikely ally: climate change. The same industrial activity that destroyed the river has helped drive global warming, with Paris’ average temperature already 4.1°F (2.3°C) higher than in Rabelais’ day. The urban heat-island effect, in which buildings and paved roads absorb more heat than vegetation and water do, is making matters worse, driving Paris’ temperature up by as much as 14.4°F (8°C) than nearby rural areas during heatwaves. Local government forecasts that Paris will have a climate comparable to Seville, south Spain’s, by the end of the 21st Century.
“We have to adapt Paris to the future and yet, this is one of the most densely populated cities in the world, and on top of that, it’s a historic city with lots of heritage restrictions, so we are limited in what we can do,” says Dan Lert, Paris’ deputy mayor for climate, water and energy. “La Bièvre is one of the great tools that we have.”
Being one with the natural world
Like trees and plants they help to cool the surrounding area. Bodies made of water can absorb heat from the atmosphere and then evaporate the heat, decreasing the surface temperature. You can make your city more comfortable by providing rainwater where it is needed. Parisians will be glad to have a long-lost waterway back. Paris Mayor Anne Hidalgo’s Socialist Party proposed “the rebirth of la Bièvre” during elections this year. A feasibility study is underway and Lert expects to complete the first section within city limits by the end of the mayor’s current term in 2026. It will join several stretches of the Bièvre uncovered over the last few years in smaller towns, in parks and other underdeveloped areas.
The Bièvre is far from the first urban river to get a new chance at life in the climate change era. A movement to “daylight” rivers has been building for roughly a decade. Auckland, New Zealand took away thousands upon thousands of cubic metres of clay and pipe to expose streams in the city’s center. A construction crew from Manchester in the U.K. discovered a section of River Medlock in its downtown area. It was hidden in an underground tunnel for 50 years. Authorities in New York City are currently studying a $130 million plan to reopen the Tibbetts Brook in the Bronx, which was enclosed in a drain around the same time as the Bièvre, to help mitigate growing flood risks.
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The trend represents a reversal among urban leaders, who for centuries saw limiting nature’s footprint as crucial to development, says Snigdha Garg, head of adaptation research at C40, a coalition of 97 cities seeking to be climate leaders. Paris and 30 other cities signed the C40 pledge in July to increase blue-green spaces within their city by 2030. This included a goal to either cover 30%-40% or ensure that 70% of residents live within 15 minutes.
“We are seeing that it’s moving away from nature—whether that’s the true course of a river or where trees should be—that is causing many of our problems,” Garg says. “And now, gradually, cities are learning to live with nature.”
Keep the air conditioner off
On July 25, 2019, Paris recorded its highest temperature in history, at 108.7°F (42.6°C). According to a September government study, unusually long and intense heat waves that the city experienced in 2018 and 2020 will soon become more common during summertime, possibly stretching into spring or autumn, according to a report.
Paris has to adapt to the new climate. However, city officials want to steer clear of one particular measure. “We want at all costs to prevent Parisians resorting to individual air conditioning systems; unlike U.S. cities, it’s not yet an established custom here,” Lert says. Though hotels, shops and restaurants sometimes offer AC, it remains exceedingly rare in Paris’ private homes, which were mostly built in a pre-AC era.
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Although they cool a building inside, the AC units can also vent heat outside into the city. A city-commissioned study found that if use of individual units became widespread across Paris, it would increase the outside temperature by 3.6-5.4°F (2-3°C) during heatwaves. That’s not even to speak of the surge in greenhouse-gas emissions that would come from an increase in AC usage, which would threaten the city’s 2050 net zero target.
Instead, to keep Paris cool, officials want to rely largely on greenery (with 170,000 trees to be planted by 2027) and the city’s rivers. Paris has a district cooling system—an environmentally friendly technology that uses water or another medium to move heat from hotter areas to naturally cooler ones—that’s the largest in Europe. Construction in 1991,The chilled water is pumped from the Seine through 56 miles (90km), of pipes. It cools offices, hotels, museums, shops, offices and other buildings. In the coming 20 years, it plans to increase the length of the network by doubling its size and link all the hospitals and other healthcare facilities.
Parisians will have more chances to enjoy a swim if there is a push to improve the rivers. The city hopes to fulfill its long-held goal of making the Seine accessible for swimming by the 2024 Summer Olympics. Years of incremental improvements to water quality, thanks to better waste management, have already allowed the city to open, in 2017, a free-to-use swimming area in the eastern Canal Saint Martin: the pool’s waters are separated from the rest of the canal only by a mesh filter to keep out leaves. Each summer, it receives approximately 100,000 people. To allow swimming in the Seine—a much bigger and harder to control waterway—the city is taking a bolder step: constructing a 46,000-cubic-meter underground water tank currently in the works near the Gare D’Austerlitz, a central train station. The underground water tank is designed to store excess water during storms. It will also prevent the sewers from overflowing, spilling dangerous bacteria and flooding the Seine.
The symbol of progress
The Bièvre also owes its likely rebirth to improvements in water quality. The river’s foul content caused smaller communities along its path to either divert or pave it over in the early 1900s. But over the last two decades, the regional Seine-Normandie Water Agency has worked to fix poorly made pipes that leaked wastewater into the Bièvre, and tightened monitoring of the homes and businesses located along its course. The water quality is now good enough that several towns have been able to uncover stretches of the river, each citing heat and flood risks from climate change as the reasons to do so: at L’Haÿ-les-Roses, 3.5 miles from southern Paris, in 2016; at Massy, 8 miles away, in 2018; and at Jouy-en-Josas, 11 miles away, in May of this year.
In the spring of 2022, Arcueil, a densely populated suburb just outside Paris’ city limits, will reopen a 0.37 mile (600m) stretch of the Bièvre, at which point its waters will also begin flowing through underground channels in Paris, meeting the Seine again (and technically contributing a little water to the district cooling system). Rainy days will see the water diverted to an underground treatment facility. “The fact we can do this shows we’re going in the right direction on water quality,” Lert says.
The first Parisian section of the Bièvre to reopen will be in Parc Kellerman, a public park on the southwestern edge of the city. It would take two or three six-year mayoral terms, Lert says, to uncover all the possible sections of the river—those that won’t require demolishing buildings or other infrastructure—up to where it meets the Seine. At current exchange rates, the cost of this project is approximately 14 million euros. Half the amount will go to city hall. The other half will go to the greater Paris metropolitan Authority and to the regional water agency.
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Daylighting a river is almost always an expensive process, according to C40’s Garg. But, as with many costly climate adaptation projects, “the cost of damages, from heat and flooding, will be even higher if you don’t do it,” she says. Seoul constructed a $900million artificial Cheonggyecheon stream, which was built on top of an original river. The highway had covered it up in the 1970s. By diverting water from underground rivers, the new waterway acts as a flood-relief channel and can shield surrounding areas from a 200-year-long storm. Cheonggyeon is also a popular tourist attraction. It receives 60,000 people per day and has been credited for revitalizing an economically poor neighborhood. “Financially, there’s a clear case for these projects,” Garg says.
For Parisians, the rebirth of the Bièvre also represents a chance to assuage a distinctly French cultural guilt over its destruction. “The Bièvre disappeared because of the disregard of residents,” three local historians bemoaned in a book about the river published in 2002, during the last push to reopen it. “Just maybe, the new interest in the river will open a new era, in which humans will learn to live while respecting their environment.”