Walking in Stockholm one evening four years ago, about to cross a bridge from an old part of the city to an even older part of the city, I came to a weird round, concrete structure. It was decrepit; its crumbling walls were completely covered with graffiti; and cars were spinning around it at different levels on a great circular weave of highway ramps.
I had stumbled upon Slussen.
Slussen was one of the most ambitious urban highway experiments of the early 20th century — Le Corbusier called it “the modern era’s first large project” — and it was now about to be torn down. What had been a forward-looking project nearly a hundred years ago was now in need of urgent and radical rethinking, driven by an understanding of climate change.
Stockholm is built at the place where the fresh water of Lake Mälaren flows into the Baltic Sea. Slussen — which means “lock” — is the crucial gate between the two. Due to climate change, the city faces threats from both directions. Because of sea level rise, a six-foot storm surge from the Baltic could overflow into Lake Mälaren, contaminating the drinking water supply for over 2 million people. On the lake side, the increased water volume caused by heavier rainfalls and increased snow melt could flood the city and its massive subway and underground utility systems.
Translation: There is going to be a lot more water in the next hundred years, and the survival of the city depends on how well they plan for it.
The city and national governments are investing over a billion dollars in this project, based on scientists’ projections. No one is calling it a hoax. No one is denying its urgency.
Over the past four years, I’ve read more about Slussen, and seen some of the demolition and construction on my visits to Stockholm. The overall project, scheduled for completion in 2025, is not quite half finished. Wide new overflow channels are being dug, to let five times as much water out of Lake Mälaren when it floods. Higher, stronger floodgates will resist storm surges from the Baltic.
In addition to dealing with water, the project is a reinvention of how Stockholm handles transportation and traffic. Slussen is the hub connecting the northern and southern parts of the city, with cars, bikes, pedestrians, buses, subways, and commuter trains all passing through it. Since 2006, Stockholm has already reduced the number of cars entering the city by over 20 percent, charging congestion fees for drivers and increasing the capacity, frequency, and range of the public transit system. The Slussen project amplifies this commitment to environmentally responsible ways of getting around the city.
Instead of two bridges for cars and a cloverleaf highway interchange, there will be one bridge for cars and buses and one just for bicycles and pedestrians. A new underground terminal for buses and trams will connect to the subway station.
During the 20th century, a lot of city planning — including Boston’s Big Dig — was about adapting the city to the car. Slussen is about fewer cars. It’s about reducing greenhouse gases and planning for the potentially devastating consequences of the change that has already happened.
Last week I stood on an overpass looking down on the entire massive Slussen site. The weird round concrete structure is gone. So is the bridge I walked across on that first evening. You can see a city actively addressing cause (greenhouse gas emissions) and effect (sea level rise and storm flooding). They’re not arguing about whether it’s more important to stop climate change or fix it; they’re trying to do both. The site is a visible panorama of urban change in response to climate change. This is where we need to be going — as cities, as countries, as a world.
Joan Wickersham’s column appears regularly in the Globe.