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Friday, December 3, 2021

The man turning cities into giant sponges to embrace floods


Yu Kongjian can remember the day he nearly died in the river.

The White Sand Creek, swollen by rain, had flooded the rice terraces in Yu’s farming commune in China. Yu, who was only ten years old at the time, dashed to the river’s edge.

The earth beneath his feet suddenly collapsed, sweeping him into the floodwaters in an instant. The river’s flow was slowed by willow and reed banks, allowing Yu to grab the vegetation and pull himself out.

“I am certain that if the river had been smoothed out with concrete flood walls, I would have drowned,” he tells the BBC.

It was a watershed moment that would affect not only his life, but also the rest of China.

Yu Kongjian, one of China’s most prominent urban design thinkers and Dean of the prestigious Peking University’s college of architecture and landscape, is the man behind the sponge city concept of flood management, which is being implemented in a number of Chinese cities.

It’s an idea he believes other cities can adopt, even as some question whether sponge cities can truly work in the face of more extreme floods caused by climate change.

White Sand Creek as Yu remembers it, in a picture taken in 1984

‘Don’t fight the water’

What if a flood was something we welcomed rather than feared? Prof Yu’s sponge city revolves around this concept.

Traditional flood water management often entails constructing pipes or drains to remove water as quickly as possible, or reinforcing river banks with concrete to prevent them from overflowing.

A sponge city, on the other hand, seeks to soak up rainfall and slow down surface run-off.

It attempts to do so in three ways. The first is at the source, where a city tries to contain water with many ponds, much like a sponge with many holes.

The second method is through the flow, in which, rather than trying to channel water away quickly in straight lines, meandering rivers with vegetation or wetlands slow water down – just like the creek that saved his life.

This has the additional benefit of creating green spaces, parks, and animal habitats, as well as purifying surface run-off with plants that remove polluting toxins and nutrients.

The third component is the sink, where the water drains into a river, lake, or sea. Prof. Yu advocates for the surrender of this land and the avoidance of construction in low-lying areas. “You can’t fight the water; you’ve got to let it go,” he says.

Tianjin’s Qiaoyuan park has been held up as an example of sponge city principles in action

While similar concepts exist elsewhere, the sponge city is notable for using natural processes to solve the city’s problems, according to National University of Singapore sustainable design expert Dr Nirmal Kishnani.

“Right now, there is a disconnect… but the thinking is that we must find our way back to seeing ourselves as part of nature.”

Much of the concept is influenced by ancient farming techniques Prof Yu learned as a child growing up in Zhejiang, China’s eastern coastal province, such as storing rainwater in ponds for crops. It has earned Prof Yu and his landscaping company Turenscape numerous awards.

“Nobody would drown, even in the midst of the monsoon season. We simply coexisted with the water. When the floods came, we adapted to the water “he claims.

He moved to Beijing at the age of 17, where he studied landscaping before going on to Harvard to study design.

When he returned to China in 1997, the country was in the grip of a construction frenzy that continues to this day.

Prof Yu began advocating an urban design philosophy based on traditional Chinese concepts after being appalled by its “grey, lifeless infrastructure.”

Besides sponge cities, for instance, he calls for natural rustic landscaping or a “big feet revolution”, in opposition to overly manicured parks which he likens to the outdated Chinese practice of binding women’s feet.

He believes that China’s coastal cities, as well as other places with similar climates, have adopted an unsustainable model for city development.

“The technique developed in European countries is incapable of adapting to the monsoon climate. These cities fail because they have been colonised by Western culture and have adopted their infrastructure and urban design “he claims.

He was initially met with opposition from the establishment, some of whom were irritated by his outspoken criticism of Chinese engineering, including national pride projects such as the Three Gorges Dam.

This, combined with his Harvard education and Western accolades, earned him accusations of being a traitor and “Western spy” undermining China’s development.

Prof. Yu, who considers himself a product of the Cultural Revolution, regards this notion as absurd.

“I’m not a Westerner; I’m a Chinese traditionalist,” he jokes. “We have thousands of years of experience, and we have a solution that you cannot overlook. We must stick to our Chinese ways.”

In lobbying for sponge cities, he has deftly appealed to Chinese officials’ patriotism, aided by media coverage of his ideas following high-profile flooding disasters in Beijing and Wuhan in recent years.

It was profitable. Following President Xi Jinping’s approval, the government announced a multi-million yuan plan with an ambitious goal: by 2030, 80 percent of China’s municipal areas must have sponge city elements and recycle at least 70 percent of rainfall.

A magic bullet?

Around the world, more places are struggling to cope with more extreme rainfall, a phenomenon scientists have linked to climate change. As temperatures rise with global warming, more moisture evaporates into the atmosphere, causing heavier rain.

And they say it will only get worse: in the future, rainfall will be more intense and severe than previously expected

But with heavier storms is the sponge city really the answer?

Some experts are not sure.

“Sponge cities may be good for mild or small rainstorms, but with the very extreme weather we are seeing now, we still need to combine it with infrastructure such as drains, pipes, and tanks,” says Faith Chan of the University of Nottingham Ningbo, a flood management expert.

He also points out that in many dense cities where space is at a premium, some of Yu’s ideas, such as providing land for floodplains, may be difficult to implement.

Despite spending millions of yuan, China continues to experience catastrophic flooding.

Last summer, a series of floods killed 397, affected 14.3 million, and contributed to $21.8bn in economic losses, according to UN estimates.

Prof Yu, on the other hand, insists that ancient Chinese wisdom cannot be wrong, and that these failures are the result of local officials executing his idea incorrectly or piecemeal.

He cites the Zhengzhou flood earlier this year as a prime example. Because the city had paved over its ponds, there was insufficient water retained upstream when the rain began.

He claims that the main river had been channelled into concrete drains, causing water flow to accelerate “like a flushed toilet.” Hospitals and other critical infrastructure were constructed on low-lying land.

“A sponge city can withstand any flood; if it can’t, it isn’t a sponge city. It must be tenacious “he claims.

Another question has been raised about whether or not the sponge city concept is truly exportable.

Prof Yu claims that flood-prone countries such as Bangladesh, Malaysia, and Indonesia could benefit from the model, and that Singapore, the United States, and Russia have begun to implement similar concepts.

However, much of the success of the sponge city’s spread throughout China is arguably due to its centralised government and large state coffers.

Prof Yu claims that if done correctly, a sponge city would cost “a quarter” of the cost of conventional solutions. He claims that building on higher ground and allocating land for flooding, for example, would be less expensive than constructing a pipe and tank system.

Many of Turenscape’s projects are now aimed at repairing flood infrastructure, which costs millions of dollars, and this money could have been saved if officials had followed sponge city principles in the first place, he claims.

Using concrete to manage a flood is thus analogous to “drinking poison to quench your thirst… it is a short-sighted approach,” he says.

“To adapt to climate change, we must change our way of life. They will fail if they do not follow my solution.”

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