China's 'sponge cities' not built to withstand extreme weather events

Design strategy based on rainfall levels in the 30 years prior to 2014, says one expert

BEIJING - Flooding has affected at least 30 million people in China so far this year, with at least 20 deaths in the past few days, raising questions about the country's preparation for catastrophic weather fuelled by climate change.

China has invested billions of dollars in recent years to protect against extreme rainfall after a 2012 flood in Beijing killed 79 people and prompted President Xi Jinping to call for building "cities like sponges".

The idea is simple: Using rooftop gardens, permeable pavements, underground storage tanks and other sponge-like features to soak up heavy precipitation and then slowly release it into rivers or reservoirs.

Since then, dozens of Chinese cities from Beijing in the north to Chongqing further south have pledged to make the transformation.

But the rising death toll in northern China since Saturday has sounded the alarm on whether these tactics are fit for purpose as rising global temperatures supercharge more more intense intense rainfall events. It is becoming increasingly difficult for communities, from Vermont villages to London neighbourhoods, to keep up with the fast changes in precipitation.

Take Daxing airport, a major aviation hub on the outskirts of Beijing. Its scenic lakes, water storage tanks and drainage systems are designed to absorb rainwater that can fill roughly 1,300 Olympic-size swimming pools. Despite being the first in the country to be deemed a "sponge airport", part of its runways were still swamped as the capital battled record rain.