Trapped subway passengers tell of desperation

In Beijing, which was hit hard by unprecedented torrential rains on July 21, 2012, resulting in 79 deaths, authorities have taken measures to prevent possible disasters.

Last month, when heavy rain was forecast in the capital, many such measures were taken, such as shutting down subway lines, encouraging people to work from home and closing schools and parks.

Zhang Jin, an associate researcher of climate change at Zhengzhou University, wrote in an article that people should be prepared for the possibility of disasters.

"Torrential rain usually occurs in coastal cities, but Zhengzhou usually has very little rainfall," she wrote, adding that as a professional, she had not initially realized the danger on Tuesday.

"The tragedy in Zhengzhou shows that inland cities usually know little about urban flood disasters," she said.

Zhengzhou is one of the major Chinese cities that has spearheaded a "sponge city" program, which aims to absorb and capture rainwater for use and to control floods.

The city was chosen to pilot the program in 2016. It plans to build 73 storage ponds with a total capacity of 820,000 cubic meters and extend its rainwater drainage pipe network to 2,576 kilometers.

Lyu Hongliang, an expert with the China Academy of Urban Planning and Design, said Zhengzhou's urban flooding prevention and control capability corresponds to a city of its size.

"If the capability is designed in accordance with extreme weather at the time, it will result in serious waste," he was quoted as saying by Chinese financial media outlet Yicai.

However, Lyu stressed that it is important to design a city's disaster mitigation capability "someway beyond what is usually required".

He suggested allocating some areas especially for urban development disaster prevention and control efforts.

In addition to strengthening the drainage pipe network, more natural drainage channels, or spillways, should be built in newly urbanized areas, he said.

Zuo Qiting, a professor at Zhengzhou University's School of Water Conservancy and Engineering, said the sponge city program alone is not sufficient to cope with urban flooding as severe as that seen in Zhengzhou.

In addition to improving flood control infrastructure as much as possible and stepping up early warning systems, Zuo suggested holding more emergency drills as precautionary measures to tackle urban flooding on the scale witnessed in the city.