A project aimed at absorbing torrential rain water
"Sponge Cities" in China... a pioneering program that was disrupted by an unprecedented flood
Sponge Cities is an ambitious and costly project.
From the source
The Chinese government has invested billions of dollars in the Sponge Cities Program.
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Meteorologists warn of the possibility of hurricanes and floods in the future.
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The amount of water that fell was unexpected.
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Water resources management and flood control are very political issues in China.
From the source
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China's multibillion-dollar "sponge cities" program to mitigate urban floods using natural means faced its biggest test last week, and the weather showed the shortcomings of the innovative project.
On July 20, the landlocked city of Zhengzhou, one of the 30 cities involved in the Sponge Cities Program, was flooded by sudden torrential rain, causing massive floods in the subway system, highways, and across the city and the surrounding area. Huge amounts of rain fell in four days.
“The Zhengzhou incident is very rare and very unfortunate,” says Faith Chan, a professor of environmental sciences at the University of Nottingham-Ningbo in China, who researches sponge city projects.
The China Sponge City program aims to use sidewalks, parks, green roofs, urban wetlands, and other innovations to absorb water during storms, then filter that water and gradually release it like a sponge.
The Chinese government has invested more than $12 billion in the program, since 2014, to help cities create sponge layers on 20% of their areas, with the goal of retaining 80% of rainwater each year, or reusing it, by 2030. The program is an attempt by China to strike a balance between urban construction and environmental requirements, efforts that may provide a model for other flood-prone countries.
Although Zhengzhou has spent more than $80 million since 2016, building green belts, flexible roads with water, and collecting wells, to reduce flooding caused by heavy rains or floods from major rivers, the intensity of the rains last week inundated the region. Designed to absorb quickly.
“For this type of rain, the soil will saturate very quickly,” Chan says. “The Sponge City program is a good program, but it can only withstand a light or big storm,” which comes once every 30 years, she says.
The task ahead for China's government is not to abandon the most sustainable, environmentally friendly approach to stormwater absorption and recycling, but to pay greater attention to extreme weather conditions and uncertainty.
concrete jungle
The basis of the increasing risk of floods caused by climate change lies in the country's unprecedented urbanization, and since 1978 the number of urban residents in China has increased fivefold, to 900 million, and thus 64% of the population of 1.4 billion now lives in cities. Because highways and other buildings and infrastructure clear the land and reduce green spaces, surface flooding has emerged as the most serious urban water problem, with floods affecting dozens of Chinese cities each year.
Urban drainage systems in most Chinese cities are insufficient to cope with the increasing risks of urban flooding in light of climate change.
In July last year, more than 20 million urban residents were affected by floods in 24 provinces, according to a research paper prepared by Chinese scientists.
The problem also prompted a rethinking of the traditional flood control infrastructure in China, with 97,000 dams built since the 1950s.
Experts say the government's focus on building dams and dikes to prevent river floods has been less effective in ensuring that thriving cities are protected, especially when the rains are heavy.
Dams are often seen as flood mitigation tools, but as dams increase in size, they tend to complicate flood controls because The inability to predict climate change.
Barlow notes that two dams in Inner Mongolia collapsed due to heavy rains in mid-July.
harmonious relationship
Peking University Professor of Landscape Architecture, Yu Kongjian, is the principal architect of the Sponge City concept.
During the World Economic Forum in 2019, Kongjian described the previous approach to flood prevention as “completely wrong,” explaining, “I think we can use concrete to guide the river, we can use dams to protect the city from floods, and we can drain all the water.” “Structures like this cause flooding as well. Those gray infrastructures are actually fatal to the natural system, which we have to rely on for our sustainable future.”
Congjian believes that the sponge city contributes to a more harmonious relationship between humans and nature, which actually gives water more space to collect in urban areas, such as gardens that dry up in some seasons, or become ponds, or shallow channels in rainy seasons.
"Floods are not an enemy, we can make friends with them," says the Chinese expert.
But the amount of rain in Zhengzhou, the capital of Henan Province, located on the arid North China Plain, shocked the city and swallowed its features.
Despite the red alerts from meteorologists, 12 million people continued to go to work and school as usual when torrential rain fell, roads and parts of the subway system inundated, with about 500 people trapped for hours, amid rising waters.
Travelers cling to trees and lampposts, as water flows in huge quantities across the city, and the death toll has reached 73, according to state media.
The flood cut off electricity, drinking water, internet and phone connections in the city and outlying areas, affecting 13 million people, and forcing more than a million Chinese from their homes.
Big losses
About 182,000 hectares of agricultural crops, and thousands of pigs and other livestock on surrounding farmland, have been wiped out in the area known as China's "breadbasket", increasing the total economic damage estimated at more than $10 billion.
Experts said the recent flood highlighted the need to tackle the problem of waterlogging in cities.
In this, the director of the Institute of Public and Environmental Affairs in Beijing, Ma Jun, says, “It is clear that we need to deal with this much more seriously,” continuing, “for this to happen sometimes requires some kind of real big catastrophe,” noting that there is a “gap” in the response of the city administration. He says: "We should not waste any crisis and take that as a lesson, and the general trend of intense and heavy rain is clear."
sensitive issue
As Zhengzhou struggles to recover, the growing threat of floods is hitting the political nerve in China. The ruler's mandate since ancient times has been linked to the state's ability to "arrange water resources" through flood control, and dynasties fell when they failed in this task.
The legends of the origin of China center around the great Yu, the founder of the first Xia dynasty, who, according to legend, dug river basins in the North China Plain, where the Yellow River now flows through Zhengzhou.
“Throughout history and in the 20th century, water resource management and flood control have been very political issues in China,” says Sabrina Habich Sobegala of the Institute of Chinese Studies at the Free University of Berlin.
Reflecting this sensitivity, Chinese President Xi Jinping issued "Important Instructions" on July 21, a day after the Zhengzhou flood, demanding that authorities prioritize flood prevention, "identify hidden dangers", and improve the precipitation early warning system.
Chinese flood control officials and meteorologists have warned that more heavy rains, typhoons and floods are likely in August, including in major cities such as Beijing and Tianjin.
They pledged to intensify monitoring of rivers and reservoirs, and to provide early warnings of catastrophic weather to allow timely evacuations, according to state media reports.
ambitious goals
The goals set by the government for water-sucking sponge cities are "very ambitious" and may eventually be adjusted, says Faith Chan, professor of environmental sciences at the University of Nottingham-Ningbo in China, explaining that challenges such as financial constraints and a lack of public participation due to China's policy approach. From top to bottom, slowed down the implementation.
However, environmental experts believe that the catastrophic rains in Zhengzhou, and elsewhere, will help raise awareness in China about the growing risks of climate change and the need to act in this context.
• 97 thousand dams have been built in China since the fifties of the last century.
• 900 million people live in cities in China.
Experts say the government's focus on building dams and dikes to prevent river floods has been less effective in ensuring that thriving cities are protected, especially when the rains are heavy.
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