As flooding increases, these cities are designed to work with -- not against -- the water. Here's how they're doing it
By Laura Paddison, CNN
(CNN) -- Cities' relationship with water is a fragile balance. Too little leads to parched landscapes and water shortages; too much can cause deadly flooding, washing away homes, lives and livelihoods.
Last year severe flooding caused devastation around the world, including in Nigeria, Pakistan and Australia. And it's predicted to get worse. Parts of Asia's largest cities are projected to be underwater by the end of the century. US coasts are expected to see 10 to 12 inches of sea level rise by 2050.
To protect themselves, cities have tended to focus on trying to keep water out, often turning to concrete: Building up walls, dams and other "gray infrastructure."
"This approach works well when it is possible to predict the extent and volumes of flooding events, but has serious limitations in the current climate unpredictability," Elisa Palazzo, senior lecturer at UNSW Sydney's School of Built Environment, told CNN.
As the climate crisis continues to threaten cities and reshape coastlines, it's prompted some to try a different way. These vulnerable urban areas are looking to work with, rather than against, water by incorporating it into the fabric of the city -- soaking it utp when there's too much; retaining it when there's too little.
Whether these efforts can scale up quickly enough to meet the enormity of the climate challenge cities face is not yet clear. But they show the possibilities when cities stop seeing water only as a threat to be controlled by concrete.
Here's how five cities are trying to reclaim their relationship with water.
Bangkok, Thailand: 'Monkey cheek' parks
To add to the pressure, as the water levels in the Gulf of Thailand rise, the city of nearly 11 million people, which sits at about 1.5 meters above sea level, is sinking due to growing urbanization.
Thai architect Kotchakorn Voraakhom, who founded the landscape architecture firm Landprocess, has dedicated much of her work to understanding how to design better for floods by asking: "What if we could design cities to work with nature instead of against it?"
"Climate change is causing cities to sink, and our current infrastructure makes us even more vulnerable to severe flooding," she told CNN.
One of her solutions for Bangkok is Centenary Park at Chulalongkorn University in central Bangkok -- a rare green space in a city with a dearth of them.
Completed in 2017, the 11-acre park (45,000 square meters) is designed to work with and capture water. Built on a slope, it is able to funnel water through its gardens and artificial wetlands, then into a retention pond.
Perhaps its most ingenious feature lies out of sight. Underneath the park are underground tanks able to hold 160,000 gallons of water. Altogether the park can hold up to one million gallons of water.
The concept for the park came from the idea of monkey cheeks, Voraakhom told the New York Times. Monkeys use their cheeks to store food to eat when he's hungry; that's what the park aims to do with water.
Green spaces can also help reduce air pollution and reduce the urban heat island effect, where dense, concrete-heavy cities trap heat. While Centenary Park is only a tiny slice of the city, Voraakhom said it's an example of what can be done.
Beijing, China: Sponge cities
China, which suffers from both flooding and drought, has long been an advocate of "sponge cities." The idea is to enable cities to soak up and retain excess water with designs focused on nature, including gardens, green roofs, wetlands and permeable sidewalks -- allowing water to both sink into the ground and flow outwards.
In 2015, the government announced a pilot scheme of 16 sponge cities, prompted in part by severe flooding which hit Beijing in 2012, killing nearly 80 people and causing widespread damage. Many more projects have since been added.
"All cities are trying to resist water like an enemy," said architect and professor Kongjian Yu, founder of design firm Turenscape and the pioneer of sponge cities. The aim of sponge cities is to "give water more space," he told CNN.
Yongxing River Park in Beijing is one of Yu's many sponge city projects. Formerly a concrete drainage channel, Turenscape turned it into a "sponge river," designed to manage floodwaters and filter rainwater.
A network of paths connects the park, which is full of plants and trees, including willow, crab apple and hawthorn trees. It also has playgrounds for children as well as a sports ground.
As sponge cities proliferate in China, there have been some questions about their ability to cope with heavier rains and storms, made more severe by climate change. In 2021, the city of Zhengzhou, in Henan province, which is part of the sponge city initiative, experienced devastating rains that killed almost 300 people.
But for Yu, sponge cities offer a necessary correction to the mistakes that have been made as cities grow, including damaging and destroying rivers and wetlands and heavy reliance on concrete.
Amsterdam, the Netherlands: Turning homes into boats
The Netherlands, around a third of which lies below sea level, is trying to work with the water by literally building on it.
And over the last few years, the idea of floating homes has been slowly gaining traction.
In the northern Amsterdam neighborhood of Schoonschip, architecture firm Space&Matter has designed a community of 30 houses on the water. Construction was completed in 2021 and it's now home to more than 100 residents.
"The thinking behind floating homes comes like logic when living in a city like Amsterdam. Water and land are interwoven," said Jeroen Dellensen, one of the three founders, along with Jaspar Jansen and Chris Collaris, of design firm i29, which designed one of the houses in the community.
Built with timber frames and insulated with burlap and straw, the homes are equipped with heat pumps and solar panels. Roof gardens aim to help them cool in the summer as well as absorbing rainwater.
A flexible jetty connects the houses with each other and to the land. They are designed to rise and fall with the ebb and flow of the water.
"Schoonschip seeks to serve as a prototype for how to deal with coastal and delta regions under pressure. Instead of fighting rising sea levels, we should adapt to and embrace the water as an urban condition," Tjeerd Haccou, co-founder of Space&Matter, told CNN.
The community is designed to withstand changing water levels over the next few decades, but it will need extra infrastructural support to resist the much higher sea levels projected beyond that, Haccou said.
The Maldives: Modeling a city on a brain coral
Few countries are more at risk from the climate crisis than the Maldives. The vast majority of the archipelago of more than 1,000 islands in the Indian Ocean sits less than one meter above sea level.
The threat of flooding, combined with a need for more housing, is driving a project from the government -- in partnership with developer Dutch Docklands -- to build a new floating city.
It's a kind of "techno city ... [but] with the look and feel of an old fisherman village from the Maldives," Koen Olthuis, a founder of Waterstudio, the firm designing the city, told CNN.
Located on a lagoon about 10 minutes by boat from the capital Male, the city will be made of a series of floating units which are built locally and towed out into the water. They will be attached to the seabed on telescopic stilts which will allow the city to rise and fall with the waves and cope with rising sea levels.
Olthuis said the environmental impact was rigorously assessed. The design is based on a brain coral and its ability to find "a balance between space and openness," he explained, adding that the city would look like such a coral from above. The aim is a dense city that provides enough space for people while ensuring enough sunlight reaches the seafloor beneath it. Artificial coral banks will be attached underneath the city to create coral ecosystems.
Construction starts in earnest toward the end of this year and is expected to be completed by the start of 2028.
Floating cities have been criticized for offering housing solutions that will be too expensive, but Olthuis said affordability was a requirement set by the government in the Maldives. The aim is for 90% of residents to be local to the Maldives and the houses will be at the same price level as similar properties in Male, he said.
"There is a growing need for these kinds of developments," said Olthuis, who said his firm has had many requests about floating cities: "Not because people love the idea of living on water, but because it can be a solution for the need for space and safety caused by the effects of climate change."
Copenhagen, Denmark: Building a giant 'climate park'
In 2011, Copenhagen experienced a cloudburst -- a very sudden and destructive rainstorm which unleashed months' worth of rain over a few hours, leaving parts of the city under a meter of water. Damages were extensive, estimated at around $1 billion.
The disaster supercharged the city's climate plans. One of its responses is Enghaveparken -- a huge "climate park."
The park, which dates back to 1928, was redesigned by architectural firm Tredje Natur (Third Nature). "It was kind of a catch 22 situation," Fleming Rafn, a founding partner of Tredje Natur, told CNN. They had to work out how to preserve the park's heritage, while preparing it for a future of more extreme climate events.
The redesigned park, which lies at the bottom of a hill, is based on the idea of having chambers for water.
A concrete hockey court was lowered 3 meters, and will be the starting point for containing flood water. After the court fills up, water can flow on to a sunken rose garden and finally to the lake. The park also has subterranean basins, which harvest rainwater from the neighborhood.
A perimeter wall around the park will keep water contained and was built in a way that meant all the historical trees could remain where they were, Rafn said.
In extreme 100-year events, the whole 35,000 square meters (380,000 square feet) of park can be filled with water from end to end, where it can be contained until floods have eased enough for the water to be released into the sewer system. The park can handle around 6 million gallons.
The aim is to reconnect people with nature and the impacts of the climate crisis, Rafn said. "It's so difficult for us to understand climate and our own relationship with it, and how do we as individuals actually participate in something that is this abstract, and I think making it tangible has a large promise in terms of making it more of a down-to-Earth discussion."
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