MAKING A SPLASH: Residents catch fish on a flooded road in Xiamen, Fujian Province, after a torrential rain brought by a tropical storm on July 19 (FENG XIAOFEI)

People in many cities across China have experienced disruptions due to urban drainage failures since the beginning of summer.

Kunming, capital of southwest China's Yunnan Province, was forced to grapple with urban flooding after the heaviest rainfall of the year hit the city on July 18. During the next three days, flooding of local roads submerged cars and taxis and rendered more than 200 inundated buses unusable.

In the wake of a tropical storm that swept southeast China's Fujian Province, the coastal city of Xiamen, was severely flooded on July 19. In some areas of the city, water reached waist-high levels, while pedestrians caught fish that had escaped from ponds and aqua farms.

While reading such reports, citizens in Beijing may be reminded of the city's most deadly rainstorm from one year ago. The heaviest rain in six decades struck the capital on July 21, 2012. The 16 hours of nearly constant downpour wreaked havoc on Beijing's infrastructure and left 79 people killed in rain-triggered disasters and accidents.

The primary reason for urban flooding is that drainage systems often lag behind overall urban development, said Xu Ke, a senior engineer with the Beijing Tsinghua Tongheng Urban Planning and Design Institute.

He said that another major cause is that some roads are built higher following maintenance projects, leaving lower-lying roads more vulnerable to flooding in heavy rainfall.

Mounting risks

In recent years, frequent urban drainage failures have forced governments of many cities to establish emergency plans.

Rainstorms brought by typhoon Krosa slammed Hangzhou, capital of east China's Zhejiang Province, in 2007. Streets were flooded to such an extent that many residents resorted to using canoes for transportation.

Starting in 2008, the local government began raising standards for drainage pipelines used in new projects and applying these in old city areas. Meanwhile, for identified vulnerable areas, municipal authorities have established an emergency plan to designate personnel and pumps to key spots during downpours to prevent waterlogging.

But this method has shown only limited effectiveness. During a rainstorm on June 24, Hangzhou was still paralyzed by floods in spite of drainage workers being assigned at 18 key stretches of roads and 14 residential communities beforehand.

The failure of Hangzhou's emergency drainage plan during this year's flood season highlights the need for a national effort to solve this problem once and for all. In April, the State Council issued a notice on upgrading urban drainage facilities. Accordingly, China will achieve a drainage network upgrade to separate rainwater from wastewater within the next five years and build sound urban drainage systems within the next 10 years.

On June 18, the Ministry of Housing and Urban-Rural Development (MOHURD) issued a guideline for local urban governments to formulate plans on improving their drainage systems. It says that by 2017 drainage facilities in downtown areas across the 36 largest cities would be upgraded to handle torrential rain occurring once every 50 years; drainage facilities in downtown areas of all other prefecture-level cities would be able to withstand heavy rain occurring once every 30 years, and drainage facilities of all other downtown areas would be able to cope with heavy rain occurring once every 20 years.

According to a survey conducted by the MOHURD in 2010, between 2008 and 2010, 62 percent of cities in China experienced severe flooding at least once; 137 cities reported this problem three times or more and real estate or other facilities were submerged more than 12 hours in 57 cities.

Data from the Office of State Flood Control and Drought Relief Headquarters show 258 cities in China suffered from heavy inundation during 2010, mostly caused by urban flooding in the wake of torrential rains.

Cheng Xiaotao, Executive Deputy Director of the Water Hazard Research Center under the Ministry of Water Resources, told newspaper China Business News that urban flooding has posed a more prominent threat to cities in China than externally sourced floods while laws, regulations and emergency plans on flood control have yet to differentiate responses to both types of disaster. "A clear understanding of the different causes for such water hazards is the key to reducing urban flooding," he said.