For centuries, China’s response to its unruly rivers has been to try to restrain them with levees, dams and canals.
China’s National Climate Centre has records of natural disasters going back 500 years, and in almost every one of them there was a major flood.
Yet the rivers continue to burst and China’s rapid urbanisation is making things worse.
Former flood plains have become houses and factories, protected by ever-higher embankments.
So the government is trying a new approach.
On the northeastern fringe of Chongqing, around the giant new international exhibition centre, the rising district of Yuelai is designed as a “sponge city”.
China’s cities flood partly because most of the water-retaining land that used to absorb rainfall – grassland, woods and lakes – has been paved over, forcing rain to flow directly into poorly built or outdated sewage and drainage systems that can no longer cope.
The “sponge city” initiative, launched in 2015, is an attempt to reverse that – soak up heavy precipitation and release it slowly into the river and reservoirs.
Using features such as rooftop gardens, scenic wetland parks, permeable pavements and underground storage tanks, the plan is to eventually absorb or reuse 70 per cent of the rainwater that falls on four-fifths of China’s urban land.
Yuelai is one of the pilot sites approved by the central government. Its Exhibition Centre Park is set lower than the surrounding ground to collect rainwater, which is filtered by layers of aquatic plants.
Rain falling on rooftops is diverted to nearby parks, while sidewalks are made of absorbent materials.
It seems like a positive sign for Chongqing, built among mountains where two major rivers meet – the Jialing and the Yangtze.