Eleven inches of rain chucked down on Beijing on July 21, 2012, flooding roads and filling underpasses. Landscape architect Yu Kongjian barely made it home from work. “I was lucky,” he says. “I saw many people abandon their cars.” As the deluge continued, the city descended into chaos. Beijing’s largest storm in more than 60 years killed 79 people; most of them drowned in their vehicles or were sucked into underground drains. Damages reached nearly $2 billion.
To Yu, co-founder of the internationally acclaimed landscape architecture firm Turenscape, the disaster was avoidable, a consequence of heedless development. He had warned the city government several years earlier, after he led a research team mapping the metropolis’s “ecological security pattern,” identifying land with high flood risk that should be left undeveloped and used to manage stormwater. “The 2012 flood gave us the lesson that ecological security patterns are a life-and-death issue,” he says.
A similar story has played out across China. Sixty-two percent of its cities flooded between 2011 and 2014 alone, imposing $100 billion in economic losses, according to the Chinese Ministry of Housing and Urban-Rural Development. The floods are partly the result of stronger storms fueled by climate change. But the harm is mostly self-inflicted: intensive urbanization over the past 30 years has gobbled up wetlands, felled forests, paved over farms and grasslands, and channeled rivers in concrete straitjackets, leaving stormwater that once filtered into the ground nowhere to go but up.
Urban sprawl is exacerbating water scarcity in China, too. Buildings, streets and parking lots block rain from recharging aquifers. Instead drains and pipes funnel it away—lunacy in a place with water shortages, Yu thinks. Like other cities in China’s north, Beijing is pretty dry outside of the summer monsoon season. For decades it has pumped groundwater to supply its growing population and consumption. The city is lowering the water table about a meter a year, causing the ground to sink as well.
Cities worldwide share similar problems because of development and the attempt to control water with “gray” infrastructure—concrete dams, levees, stormwater tanks, pipes and walled-in rivers whose floodplains are covered with buildings. Experts are recognizing that by breaking the natural water cycle, municipalities are raising the likelihood and severity of flooding, causing disasters from Houston to Chennai, India.
Yu is at the forefront of a global movement of urban planners, water managers, ecologists and engineers who are trying to restore natural water cycles. The work is a kind of un-engineering: giving water space to expand and contract to lessen flooding and slowing it down so it can soak into the ground, preventing shortages later. Practitioners preserve or restore floodplains and wetlands, unearth buried creeks, and create bioswales, retention ponds, sunken parks and permeable parking lots. Unlike hardscapes, green infrastructure can also clean water and re-create habitat for wildlife. And it gives urbanites access to nature, an amenity increasingly recognized as a pillar of mental health.
Local landscape design projects are popping up everywhere. But Yu and other leading practitioners are looking to manage water at a grander scale: an entire city, an entire watershed. Known as green infrastructure in Europe, low-impact development in the U.S. and sponge cities in China, these approaches mimic nature as much as possible, says Tony Wong, an engineer and chief executive of the Cooperative Research Center for Water Sensitive Cities, based in Melbourne, Australia. The goal is to create water infrastructure that “functions as a living organism,” he says.
The sponge cities movement is gaining momentum. In March 2018 the United Nations released a report called Nature-Based Solutions for Water that supports the approach. The U.S. Army Corps of Engineers, infamous for its muscular engineering of rivers and wetlands, now has an Engineering with Nature initiative. After centuries of dikes to enclose rivers and low-lying land, the Dutch are onboard, too. A near disaster in 1995, when water rose in the Rijn, Maas and Waal rivers, forcing 250,000 people to evacuate, prompted the government to create a countrywide program called Room for the River. Instead of only building bigger dams and dikes, Dutch officials increased the capacity of river deltas by asking farmers to agree to move or to let their land flood as necessary.
China, with its rapid growth and centralized government, is pursuing sponge cities on a scale difficult for most countries to even consider. The ambition is impressive. Yet Yu is finding that he still has to overcome a tendency among planners toward one-size-fits-all approaches, which could be disastrous because each location has unique hydrological systems and needs. He is also confronting a penchant in his country for stronger dams, bigger pipes and larger storage tanks, which symbolize power and progress in modern China.
Mr. sponge city
On a spring day in Beijing with a “very high” air pollution rating, I visited Yu at Turenscape’s headquarters in the city’s Haidian District. A slim, intense man in his 50s, with sharp eyes and just a bit of gray at the temples, Yu traces his passion to the agricultural commune where he grew up in Zhejiang province southwest of Shanghai. There he observed the Chinese “peasant wisdom” for managing water, practiced for thousands of years. Farmers maintained little ponds and berms to help rainfall infiltrate the ground, storing it for a dry day. The creek next to his village swelled during certain seasons, which no one saw as a threat. “If you have wise ways to deal with flooding, water can be friendly,” he says.
Since starting Turenscape in 1998 with his wife and a friend, Yu has built the award-winning company into a landscape architecture empire with 600 employees. The company has more than 640 projects built or underway in 250 Chinese cities and 10 other countries, including a redesign of the Kaban Lakes system in Kazan, Russia. Yu is dean of the school of landscape architecture at Peking University and has taught periodically at Harvard University.
For years while Yu was building his firm’s portfolio, many Chinese derided his farm-based ideas as backward. He says that some even called him an American spy—a nod to his doctorate from Harvard’s Graduate School of Design and his opposition to those big dams. But in recent years sentiment has begun to shift. Various groups in China are building green infrastructure projects, often in partnership with Americans, Australians and Europeans. Yu’s influence has been growing in parallel. He lectures regularly at the Ministry of Housing and Urban-Rural Development, and his 2003 book about his practices, The Road to Urban Landscape: A Dialogue with the Mayors, has been printed multiple times in China. Dignitaries such as the Mexican ambassador to China, who is hoping he can solve Mexico City’s water problems, ask for his input.
The 2012 Beijing flood was a turning point. Soon afterward, a Turenscape stormwater project in Harbin won a top U.S. design prize. China Central Television broadcast a long, high-profile interview with Yu. A government minister told him afterward that Xi Jinping, who would soon become president, had seen it. About a year later the president stood before China’s central urbanization conference and announced his Sponge City initiative, elevating the idea from struggling concept to national goal.
In 2015 the government initiated 16 demonstration projects, each covering at least 10 square kilometers. Today there are 30. The objectives include reducing urban flooding, retaining water for future use, cleaning up polluted water bodies and improving natural ecosystems. By 2020 each project is supposed to retain 70 to 90 percent of the site’s average annual rainfall. Premier Li Keqiang said in his 2017 government work report that sponge city construction will continue to expand.
A river reconstructed
A week after meeting yu, I visited one of Turenscape’s latest projects, Yongxing River Park, in a Beijing exurb called Daxing. “Before” satellite pictures from three years ago show open land surrounding the river, already straightened and confined by steep concrete walls. “Now” pictures are chockablock with buildings. Showing me the park are two of Yu’s employees, Geng Ran, who goes by Katie when talking to English speakers, and Zhang Mengyue, aka Sophie.
The government recognizes that development reduces rain infiltration, Zhang says, so it invited Turenscape to design a park that would enlarge the riverbed to hold more water. The project was nearly completed when I saw it in early April 2018. About four kilometers long and perhaps two city blocks wide, the park follows the river. We stand on a large berm that divides the riverbed into two channels. The river flows on our right; on our left the channel has big dirt holes of varying depths. During the dry season, the holes will be filled with partially cleaned effluent from a sewage treatment plant. Wetland plants in the pools will further clean the water, Geng says, and filter some of it into aquifers. During the monsoon, the channel will be reserved for floodwaters, and the effluent will be treated industrially.
“We say you can’t stop the weight of the river,” Geng says, “so that’s why we enhance this river.” Turenscape’s plan involved removing concrete along the river and excavating soil to widen the bed. That dirt was then molded into the big berm. Thousands of small sedges planted in closely set rows now dot those riverbanks, holding the earth in place. They remind me of Georges Seurat’s pointillism. Turenscape projects use native plants because they “are adapted to the local environment,” Yu says, “and need no supplemental water.”
Earlier installations are already demonstrating their efficacy. Yanweizhou Park in Jinhua, near where Yu grew up, absorbed a 100-year flood, protecting the city. Shanghai’s 14-hectare (34.6-acre) Houtan Park cleans up to 2,400 cubic meters (634,000 gallons) of polluted river water daily, improving the water’s quality from grade V (unsuitable for human contact) to grade II (suitable for landscape irrigation) using only biological processes.
Projects like these are most effective when they connect to other green infrastructure throughout the watershed, enabling water to flow in an approximation of its natural path. Across China, whole new cities being built from scratch show what is possible. Turenscape has completed part of the ambitious Wulijie Eco-City in Hubei province. Wulijie’s design preserves the natural wetlands for catching and cleaning stormwater on-site. This approach reduced construction costs for underground drainage pipes and conserved habitat for wildlife and vegetation. Buildings have roof gardens and living walls, and pedestrian and bike paths thread through the green space, all of which should enhance quality of life for residents.
It’s not easy to make space for water in an environment that has already been built, however. Architects have to shoehorn tiny projects into existing infrastructure. In Houston, for example, developers often limit themselves to building bioswales in new apartment complexes. In San Francisco, workers have been jackhammering bits of sidewalk and roadway medians to make room for plantings.
Hence the appeal of derelict industrial sites ripe for dramatic reclamation. Turenscape oversaw the first phase of such a project in the 1,000-year-old city of Kazan, which surrounds three oxbow lakes on the Volga River. During the Soviet period, pollution had killed nearly all life in the lakes. Moreover, the city was prone to flooding because of the way dams were built. When waters would rise, the city’s seven pumping stations could not keep up.
Turenscape’s design, which is partially complete, calls for reclaiming 11 square kilometers of land for floodwater along the river and its tributaries. There the city is building linear parks, promenades and bioswales that slow, absorb and clean urban runoff before releasing it into the lakes. Walking and biking routes give people access to the riparian zone and support human-powered transportation throughout the city.
Such extensive redesigns are encouraging Yu to dream beyond sponge cities to what he calls “Sponge Land.” His inspiration is to take care of the national landscape. “Water is a system,” he says, bigger than cities.
Inspired in part by American landscape designer Warren Manning, who created “A National Plan” for the U.S. a century ago, Yu is working on a landscape master plan for all of China. “That is an incredible vision,” says Niall Kirkwood, a professor of landscape architecture and technology at the Harvard Graduate School of Design, who has known Yu for many years. “No one thinks at that scale and with that political savviness.”
Yu’s office walls display maps of China that document elevation, watersheds and flood paths, as well as biodiversity, desertification, ecological security, soil erosion and cultural heritage. For his big plan, Yu can use them along with geographic information system (GIS) and satellite imagery to track China’s landscape changes as urbanization spreads, as estuaries and deltas silt up, as water starts to move differently across landscapes and cityscapes. He can isolate priority areas where projects will have the biggest impact. Kirkwood says this is like applying acupuncture to the human body. Yu “has the understanding that doing a piece of work in one area will have an effect in another area,” he says. Compared with most landscape architects, Kirkwood says, Yu is “thinking much more holistically.”
Custom solutions needed
Yu’s house, a duplex of side-by-side apartments where he and his sister live, is a personal testament to his ideas. Between the two apartments is a living wall Yu built of porous limestone. Water captured from the roof dribbles down its face, from which maidenhair ferns and philodendrons sprout. The green wall cools the two homes enough that they do not need air-conditioning, he says, although he concedes that it gets a bit warm in summer.
Decks off the bedrooms are watered with roof-caught rain, stored in tanks under plant beds. Yu’s deck smells great, emanating whiffs of rosemary, lemongrass and Chinese chrysanthemums. It even has a tiny creek in which goldfish swim. On the other side of the wall, his sister’s deck has terraced beds replete with lettuce and chard. “We collect 52 cubic meters of stormwater [annually], and I grow 32 kilograms of vegetables,” Yu says proudly.
The ideas engineered into Yu’s house are widely applicable to buildings, but each sponge city design must be unique, factoring in the site’s local climate, soil and hydrogeology. “Every patient needs a different solution,” as Yu says. There is a danger that, in their haste, Chinese planners will ignore this fact. If they do, the broad ambition for sponge cities may falter, says Chris Zevenbergen, an expert in urban flood-risk management at the IHE Delft Institute for Water Education in the Netherlands and a visiting professor in Nanjing and Chengdu. The tendency to hurriedly pursue cookie-cutter solutions in erecting cities over the past 20 years did not allow builders time to understand imperfections in design and adjust. That is why so many cities have ongoing problems with floods, he says. Copycat implementation of sponge cities could lead to similar problems. Xi’s program has strict deadlines, which may not provide time to monitor performance and adjust if necessary, Zevenbergen says.
A paper written by Chinese government research institutes in 2017 expressed similar concerns. To provide guidance, the government has formed a committee that is composed of civil engineers, economists and landscape architects, including Yu.
The sponge city vision faces other challenges. It will take private investment to fully implement the national plan. But Yu worries that companies might find pipes or dikes—things they can charge for—more attractive than sponge cities’ embrace of natural systems.
The stakes for the grand vision go beyond tempering floods and drought. Xi also wants sponge cities to deal with another big water issue China faces: pollution. Nutrients, heavy metals, pesticides and microplastics taint surface waters in China, according to Randy Dahlgren, a scientist at the University of California, Davis, who specializes in soil and water chemistry and has worked in Zhejiang province. “If they can get this water to infiltrate into the ground, a huge number of these potential contaminants will be retained within the wetlands systems, buffers, detention basins and bioswales,” he says.
Wetlands cannot just be built and forgotten, however. Phosphorus, heavy metals and some nitrogen can accumulate in the plants and return to the soil when those plants die. “You really need to be harvesting those plants,” Dahlgren says. They can be made into biomass fuels and incinerated, although some pollutants such as metals gather in the ash, which must be disposed of. “It does take active management of wetlands to make them an effective sink for a lot of pollutants,” he says. Planners should also be cautious about “trading a surface-water pollution issue for a groundwater pollution issue,” where impurities could persist for tens of years to several centuries.
If the planners get it right, though, the payoff could be huge. Sponge city techniques are already reducing pollution in places such as Philadelphia. Like many U.S. cities, its stormwater runs through sewage-treatment plants, which overflow in big storms, pushing untreated sewage into rivers. With its Green City, Clean Waters initiative, the city is reclaiming land along the banks of local creeks and rivers to absorb excessive rainfall and building parks that can flood when necessary. Philadelphia also gives incentives to landowners for creating rain gardens, green roofs, urban farms and porous pavement. These techniques allow stormwater to percolate into the ground, reducing the volume entering the sewage system. Five years in, the city had “greened” 339 hectares, enough to reduce pollution from sewer overflows by more than 5.7 million cubic meters annually.
State of flux
Natural water-management systems are not static or predictable like gray infrastructure: nature is messy. Water rises and falls. Plants sprout, live and die. Mud is exposed. Although these spaces can be beautiful—perhaps more beautiful than, say, a dam—residents might not always like what they see. For sponge cities to spread, people will have to accept a dynamic environment.
Yu calls this shift “big feet aesthetics,” a counterreference to when Chinese considered the bound, tiny feet of aristocratic women to be beautiful because they were useless, a sign that the women were too rich to work. “Now we need to find big feet attractive,” he says. “We need to change our aesthetic to find useful green infrastructure beautiful.”
Educators will need a change in perspective as well. Despite the national promotion of sponge cities, China’s schools are still training engineers using 20th-century principles, Yu says. “We are fighting so hard to try to get people to think in an ecological way.” The hubris of believing that people can control water with concrete will be increasingly exposed as more of those kinds of projects fail, unable to buffer the knock-on impacts from rapid population growth, urban sprawl and climate change. Although sponge cities will likely not protect everyone from these challenges, their advocates think their resilience can temper extremes better than the concrete alternatives. Plus the multiple benefits they bring can make the lives of humans and other species healthier and happier.