The “mushroom city” initiative was launched to increase flood resilience in China’s major cities and make better use of rainwater through infrastructure improvements.
China has been hit by devastating floods in recent weeks, inundating cities and causing death and damage to infrastructure, as well as raising questions about the effectiveness of its 2015 “mushroom city” initiative to reduce the risk of urban flooding.
The initiative was launched to increase flood resilience in major cities and make better use of rainwater through architectural, engineering and infrastructure improvements.
However, cities remain vulnerable to heavy rain. In July alone, floods and related geological disasters caused 142 deaths and disappearances, destroyed 2,300 homes and caused direct economic losses of 15.78 billion yuan ($2.19 billion), China’s Ministry of Emergency Situations said on Monday. The following is an explanation of the mushroom city scheme.
Why was the initiative launched?
China has long sought to improve the way it handles extreme weather and make highly populated cities less vulnerable to floods and droughts.
The “mushroom city” initiative was designed to make greater use of lower impact “nature-based solutions” to better distribute water and improve drainage and storage.
These solutions included the use of permeable asphalt, the construction of new canals and ponds, as well as the restoration of wetlands, which would not only alleviate waterlogging, but also improve the urban environment.
Disruptive urbanization has encased vast tracts of land in impermeable concrete, often along the banks of major rivers that traditionally served as floodplains. Since the wetlands were paved and the excess water had nowhere to settle, waterlogging and flooding were commonplace.
According to 2018 data, 641 out of 654 large and medium-sized cities in China were at risk of flooding and waterlogging, with 180 facing the risk of flooding every year.
What has been done so far?
Studies show that many of the local pilot initiatives launched so far have had a positive effect, as low-impact projects such as green roofs and rain gardens reduce water runoff.
However, implementation has so far been patchy. A total of 30 mushroom pilot cities were selected in 2015 and 2016. By last year, only 64 of China’s 654 cities had created legislation to implement guidelines for mushroom cities, researchers said in January.
The researchers said the government had so far paid “minimal attention” to the construction of mushroom cities and called for national legislation to be drawn up as soon as possible.
What are the limitations of mushroom cities?
Even if the mushroom city’s measures were implemented in full, they would not have been able to prevent this year’s disasters.
Zhengzhou in Henan province has been one of the most enthusiastic pioneers of mushroom city construction, allocating nearly 60 billion yuan to the program between 2016 and 2021. But in 2021, it failed to deal with its biggest rainfall on record.
Experts believe the mushroom city’s infrastructure can only handle 200 millimeters (7.9 in) of rain per day. During the worst rainstorm to hit Beijing at the end of July, rainfall at one station reached 745 millimeters over three and a half days. In July 2021, Zhengzhou recorded rainfall exceeding 200 mm in just one hour.
Authorities are also catching up on climate change. This year’s heavy rain has hit cities in the normally arid north, where the development of mushroom cities is less advanced.
