'Sponge City' program set to soak up urban floodwater

Learning harsh lessons

In recent years, a number of cities, including Beijing, have learned difficult lessons in urban flooding during the rainy seasons.

On July 21, 2012, Beijing was inundated by its heaviest rainstorm in 60 years. The downpour resulted in 79 deaths, caused economic losses estimated at 10 billion yuan ($1.61 billion), crippled the transportation network and left thousands of homes flooded.

This year, the Beijing Municipal Authority has taken to using social media, including popular sites such as Sina Weibo and WeChat, to warn residents of possible flooding. The authority will also expand the monitoring of flooded roads to the city's suburbs.

According to Zhang, the development of an effective early warning system is the most effective measure to reduce losses and casualties caused by urban flooding.

"The coordination of government departments is key. Flood prevention requires input from multiple government departments, so we must formulate an effective plan that will enable them to share information and coordinate effectively," he said.

Greater and more-effective information sharing would also enable the emergency services and equipment to be directed to the areas where they are most needed, he added.

In Wuhan, the capital of Hubei province, the waters of the Yangtze River, which flows through the city, have risen higher than ground level during the flood season, which has left the city's old drainage systems unable to cope, said Zhang Wenchun, head of the Luojiahu Pump Station under the Wuhan Water Resources Bureau. "We had to put all our 11 pumps to work when rainstorms have occurred," he said.

The local water resources authorities have identified all the sections of road within the city where the storm water run-off converges and stagnates.

"One of our most important jobs is to send out timely warnings to residents to stay away from those sections (of road)," said Zhang Yuntian, director of the Flood Control Information Center at the Wuhan Water Resources Bureau.

He said the bureau has employed the police video surveillance system to monitor water levels on roads so residents can be given accurate information about conditions.

Green drive

One of the most effective measures to increase the efficiency of storm drains in cities would be to reduce the storm-water runoff and raise the levels of water filtration and conservation in urban areas, experts said.

To solve the problem of urban flooding once and for all, the central government has decided to push forward the "Sponge City" program, which in part borrows the experiences of low-impact development from the United States and Canada in recent years.

Central government departments, including the Ministry of Housing and Urban-Rural Development and the Ministry of Water Resources, have selected 16 cities and districts across the country, including Xiamen, Wuhan and Gui'an New Area in Guizhou province, to be testing grounds for the program.

The program will allow at least 60 percent of rainwater to soak into the ground, rather than being discharged into rivers, according to a guide-line released by the Ministry of Housing and Urban-Rural Development in November. The level of filtration could be further raised in some areas with low levels of precipitation to increase the use of rainwater.

The project includes the development of residential communities with storage ponds, filtration pools and wetlands, plus roads and squares built with permeable materials that will allow storm water to soak into the ground more effectively, according to the guideline.

"It would require a major shift in ideas about urban construction. Rainwater should be regarded as a resource, rather than a burden to be dealt with. Concepts of urban construction should shift from the destruction of the ecosystem to its renewal," Chen Zhenggao, minister of housing and urban-rural development, told a work conference in May. Su Yonghong, an official with the administrative committee of Guizhou's Gui'an New Area, one of the 16 testing areas for the project, said it would have greater significance in older urban areas that are prone to flooding.

"If the urban runoff cannot be effectively filtered into the ground, the floods that ensue will cause the direct loss of life and property," he said.

Su said he believes low-impact development represents the future of the country's urbanization drive. "It (the dealing with storm water) is an issue of public security, thus it should be a mandatory requirement when new urban areas are being planned and built," he said.

However, he warned that funding such a program could be a major problem because it would require massive infrastructure investment.

According to Chen, the government minister, the program will require investment of 100 million yuan to 150 million yuan for each square kilometer under development.

The high levels of required funding will pose challenges for local authorities, and even though the central government will provide each city with a subsidy of 400 million yuan to develop the Sponge City project, to complete the entire program in the Gui'an New Area would require total investment of 4.6 billion yuan, he said.

"We hope the central government can provide more financial support for the program, and develop criteria to evaluate cities' ability to prevent urban flooding, so that more of them will be motivated to develop programs such as this," he said.

Contact the writer at xuwei@chinadaily.com.cn