Explainer-Why was northern China ravaged by floods?
By Ethan Wang and Ryan Woo
BEIJING (Reuters) - A Chinese river basin where 110 million people live has been hit by the worst floods since 1963 despite massive mitigation efforts, particularly during the rule of Mao Zedong, overwhelmed by the impact of global warming and outdated infrastructure.
Typhoon Doksuri, the most powerful storm in China this year, churned north in late July after making landfall in the south, bringing exceptional rainfall to the Hai river basin, a region that typhoons rarely hit, and precipitation that the Chinese capital has not seen since records began 140 year ago.
WHAT HAPPENED IN 1963?
Five rivers flow into the Hai river basin, the largest natural drainage system in northern China. The basin includes Beijing, Hebei province and the big port city of Tianjin.
In August 1963, the area was drenched by historic rainstorms, with 22 million people affected by flooding that killed 5,030 people and forced millions from their homes. More than 53.6 million acres of farmland, or 76% of the sown area, was inundated.
In response, Mao Zedong, the founder of modern China, ordered that millions work to bring the Hai river basin under "permanent control", raising thousands of kilometres of embankments and building new reservoirs and reinforcing old ones.
CURSE OF URBANISATION
Since then, China's urban population has soared, from just 16% of the population to 64% in 2022. The Hai basin is now home to 25 large and medium-sized cities.
Rapid urbanisation has meant the spread of impermeable concrete surfaces and reduced natural wetlands and marshes that had in the past absorbed rain.
Urban migration has brought a construction boom in low-lying areas, including in flood storage areas and near lakes and rivers.
China's Soviet-era urban drainage systems of shallow buried pipes leaves cities vulnerable to waterlogging during heavy rain, in contrast with cavernous underground storm "corridors" in cities such as Tokyo.
Since 2015, some 30 Chinese cities including Beijing and Tianjin have tested various flood mitigation systems, including permeable asphalt and pavements to slow water run-off but severe floods have raised doubts about their effectiveness.
CAUGHT BY SURPRISE?
Hebei's Zhuozhou, one of the cities hardest-hit by the recent deluge, was unprepared.
On July 29, China's National Meteorological Center issued its first red alert for heavy rain in 12 years, the highest level of a colour-coded warning system. But many Zhuozhou residents told state media they were not informed about the severity of the situation or told to evacuate, despite the rare warning.
On July 31, Hebei officials opened floodgates in seven low-lying flood storage areas, including two in Zhuozhou, in what officials said was an "inevitable" decision to prevent rivers bursting their banks and to protect cities downstream.
In Hebei, nearly 1 million people living in flood storage areas were relocated, with some telling media they were given just a couple of hours before floods roared into their villages.
The flood-control facilities built in the 1960s, along with increased water demand and prolonged dry weather meant that people gave little thought to the danger, said Ma Yang, vice president of civil and infrastructure for China at the AECOM infrastructure consulting firm.
Authorities should implement master drainage plans for cities and floodplain management based on a mapping of flood risks associated with rivers, Ma told Reuters.
Vulnerable cities include Xiongan, which President Xi Jinping has ordered be developed into an economic powerhouse serving Hebei, Beijing and Tianjin.
Xiongan is next to the Baiyangdian Lake, a natural flood storage zone.
(Reporting by Ethan Wang and Ryan Woo; editing by Robert Birsel)
