Climate change: China’s ‘sponge cities’ struggle to absorb flooding from severe storms despite billions of dollars in investment

These disasters have raised questions about the effectiveness of China’s climate resilience strategy against extreme rainfall, the “sponge city” initiative launched nationwide in 2015. Experts say the basic idea of ​​making cities better able to absorb excess rain is sound. But the rollout so far has turned out to be something of a damp squib. For this effort to truly hold water, infrastructure must be deployed more quickly. Still, that in itself won’t protect us from the most serious effects of climate change, experts say.

China’s State Council (Cabinet) announced the Sponge City concept in 2015. Similar to the concept of “low-impact development” in the United States and Canada, this approach calls for increasing green and blue spaces such as trees, wetlands parks, and parks. Lakes placed between traditional infrastructure such as roads and buildings. This mimics the natural water cycle and allows cities to absorb rainwater and drain or utilize it.

The government hoped that this approach would not only strengthen the country’s drainage and water management system to better prevent flooding in urban areas, but also make it a driver of economic growth. Former Premier Li Keqiang said in the 2017 Annual Report on Government Work: “We will promote the construction of sponge cities and ensure that urban areas are not only superficial but also substantial.”

The council has set ambitious targets for 80 per cent of urban areas to become sponge cities and to recycle at least 70 per cent of rainfall by 2030. As of May 2023, the government has identified 60 cities as pilot cities and is providing each city with subsidies ranging from 700 million yuan to 1 billion yuan.

According to state media, from 2016 to 2020, cities engaged in more than 33,000 sponge city projects, ranging from residential communities to parks, across 90 cities in 13 provinces, with a total investment of 1.6 trillion yuan. Reached.

Developers are also participating.

The concept is “incorporated into all of our developments, especially our mixed-use districts,” said Michael Long, director of New World Development’s sustainability group.

“For New World, we believe the sponge city concept will continue to be an important aspect of our strategic approach to climate resilience and resource conservation. [other] It’s about aspects of protecting the natural environment and how they are integrated into business decisions, from new investments to development design and asset management. ”

Canton First Estate in Foshan is a mixed-use project by developer New World China, the mainland Chinese real estate arm, spanning villas, serviced apartments and a golf course, with drainage improvements such as rainwater collection and filtration basins. It is included. Permeable pavement.

The development will be able to handle up to 4.45 million cubic meters of rainwater and gray water a year, and can withstand a once-in-50-year heavy rain event, Long said.

Despite these efforts, China’s cities remain vulnerable. Last July, cities and provinces in northeastern China, including Beijing, Tianjin, and Hebei province, were hit by extremely heavy rains and flooding due to Typhoon Doxuri. At least 1.3 million people were affected and more than 200,000 homes were damaged, according to the Beijing municipal government.

In September, Typhoon Saola hit Hong Kong and then the southern Chinese provinces of Fujian and Guangdong, displacing more than 800,000 people and canceling hundreds of flights. According to the Fujian provincial government, the incident caused the province about 870 million yuan in direct economic losses.

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Floods hit southern Thailand after heavy rains, affecting tens of thousands of people

Floods hit southern Thailand after heavy rains, affecting tens of thousands of people

Such losses raise questions about whether Sponge City’s infrastructure really works to protect the city from flood damage, after billions of yuan of investment and nearly a decade of construction.

According to water and engineering experts, sponge city mitigation is a reasonable approach to increasing resilience to heavy rains. Impermeable surfaces in urban areas, such as concrete, brick, and steel, reduce infiltration and increase the risk of flooding during storms. Sponge city infrastructure can improve a city’s ability to absorb and store water.

“China’s actions to deal with floods and heavy rains, especially the ‘sponge city’ initiative, are important strategies to proactively deal with the challenges of modern urban development and climate change,” said Li Junqi, vice president of Beijing University of Civil Engineering. he said. architecture.

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Li said many cities that have adopted the concept, such as Shanghai and Wuhan in Hubei province, have experienced less flooding during heavy rains than before.

However, such infrastructure can only manage a certain amount of rainwater. And experts say climate change is causing extreme events beyond what sponge cities can handle.

“Those who think the Sponge City initiative has failed tend to think there is a silver bullet to solving water risks,” said Mark Fletcher, global water business leader at engineering consultancy Arup. “But there is no silver bullet in the fight against uncertainty and climate change.”

For example, according to statistics from the Shenzhen Municipal Water Bureau, as a result of investing more than 2.3 billion yuan in sponge city projects from 2016 to 2022, Shenzhen is now protected from major floods that occur once every 100 to 200 years. It is said that it became Year.

However, Hong Kong authorities say September’s storm was a “once in 500 years” event.

“The challenge we face is so much uncertainty around climate change,” Fletcher said. “We’re doing some really good work on water resilience right now, like Sponge City, but as we’re seeing more and more larger and more extreme events, we’re probably going to take it to the next level like ‘Sponge City Plus.’ Maybe it’s time to move on.”

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Hong Kong flooded by ‘once in 100 years’ storm

Hong Kong flooded by ‘once in 100 years’ storm

Fletcher says it’s important to incorporate non-structural measures, such as effective forecasting and early warning systems, into urban flood protection efforts.

He said leveraging advanced technologies such as artificial intelligence and big data throughout the urban planning, forecasting and early warning process will help build resilience at different layers. For example, cities can focus on infrastructure development in problem areas or quickly redeploy people and equipment to minimize damage if flooding is imminent. He said governments need to educate the public about risks and protection methods to improve community resilience, rather than just focusing on infrastructure resilience.

Fiona Siu, director of technical services and sustainability and facilities management, said Swire Properties has incorporated the sponge city concept into projects such as Taiku Place in Hong Kong and Saviavasa in Jakarta. In the Taiku Place redevelopment project, green space has been expanded to approximately 35 percent of the site area, while in Jakarta’s luxury project, the green area is 45 percent.

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Henderson Land, Link REIT and San Hung Kai Properties have also introduced similar concepts in residential, commercial and urban regeneration projects.

However, experts say sponge city technology has not been standardized enough in urban development.

Entera Benz, founder and CEO of climate risk analysis firm Intensel, said: “There have been several user cases in mainland China about where and how to build sponge cities, but my In my opinion, it didn’t catch on.” “That hasn’t become a common standard for how we build cities.”

Governments and financial institutions should direct more investment into developing nature-based solutions that are essential to combating climate change but remain under-invested in, such as sponge city projects. It is.

In fact, a report released by the World Resources Institute in 2021 found that China faces a significant funding shortfall for climate-resilient infrastructure, with an annual funding gap of nearly 500 billion yuan over the next five years. .

The report examined the return on investment for three types of climate-resilient infrastructure, including water-saving irrigation facilities, sponge city construction, and grey-green seawalls. According to his calculations, he could earn between 2 and 20 yuan per investment over 30 years.

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Experts also stress the importance of halting climate change to avoid more frequent and severe natural disasters in the first place.

“Just by combining [climate] “Can mitigation through adaptation minimize the negative effects of climate change and ensure sustainable development of human society?” said Tsinghua University professor and director of the Institute for Climate Change and Sustainable Development. said Mr. Li Zheng. “Both are essential.”