Beijing Floods

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Posting Date: July 24, 2012, 5:00:00 AM

On Saturday, July 21, a heavy storm in China delivered as much as 18 inches of precipitation to parts of the country in and near the capital of Beijing (population 20 million). Almost seven inches of rain fell in the capital—the most since records were first kept, in 1951. According to a senior engineer from the Ministry of Transport, it rained as much in a single day in Beijing as it normally rains in six months. The 20-hour storm started July 21 and lasted until the early morning hours of the following day, Sunday, July 22. It left 37 people dead, 25 of whom drowned (the remainder died in collapsed buildings or due to electrocution). The heavy rain also flooded 700 homes, collapsed over 30 roads or bridges, and disrupted transportation at Beijing’s Capital International Airport, where more than 500 flights out of China were canceled. In total, authorities evacuated nearly 57,000 people in China. The areas hardest hit by the weekend storm were in the outskirts of the capital, in the district of Fangshan, a suburb about 40 kilometers from downtown Beijing. Fangshan received 16 inches of precipitation at popular tourist spots such as its scenic Shidu Nature Park. Meanwhile, Fangshan’s Qinglonghu village, home to a large population of migrant workers from surrounding provinces, experienced the heaviest deluge of all: 18.4 inches of rain. In the town of Zhoukoudian, 60 kilometers southwest of downtown Beijing, several bridges were washed out by floodwaters. Heavy rain also proved damaging and deadly elsewhere in China. Near Beijing, in Heibei province, 15 people were killed and 19 remain missing. In Sichuan province, in the west, six fatalities resulted from landslides. Fatalities also resulted in Shanxi province in the north, in the neighboring Shaanxi province, and in Yunnan province, in the south. According to a report by the Beijing Daily newspaper on the Beijing government website, economic damage from the weekend’s storm reached at least 10 billion yuan (USD 1.6 billion). Meanwhile, due to the many cars submerged in flooded roadways, more than 13,000 vehicle insurance claims have already been submitted to the Beijing branch of the China Insurance Regulatory Commission.

Meteorological Conditions

The deluge in and near the capital was part of a larger storm system across the country that has caused the evacuations of at least 567,000 people and killed 95 since Friday, July 20. The heavy rain was caused in part by a slow-moving cold front that was partly fed by moisture from Typhoon Vicente, a storm located well to the south, near Hainan province. (According to the Japan Meteorological Agency’s 1800 UTC advisory today, Vicente has maximum sustained winds of 105 miles per hour and is roughly 85 miles south of Hong Kong, in the open ocean). The heavy rainfall over the weekend was also a result of a favorable Madden-Julian Oscillation (MJO)—identified on satellite imagery as enhanced regions of convection, or cloudiness; favorable MJOs can further enhance precipitation. Notably, the large-scale flow responsible for this slow moving front is little changed from the one responsible for the floods in Japan last week.

China’s Flood Defenses

In the aftermath of the record-breaking flooding, questions are being raised about the quality of the capital’s flood drainage systems, on which the weekend’s storm put tremendous stress. On Sunday, in response to public concern, China’s finance ministry announced that 120 million yuan (USD19 million) had been allocated to Beijing, as well as to Tianjin (a nearby coastal city) and to the neighboring province of Hebei. The funds are for repairing “flood-damaged water conservancy facilities” and “supporting flood control in these areas.” Since the late 1940s, China has continued to strengthen flood control measures. To that end, more than 280,000 km of embankments, 86,000 reservoirs, and 97 key flood retention areas have been completed. The Chinese government claims that major rivers and lakes are capable of withstanding a 100-year return period flood event, while major sea dikes defend up to the 50-year level. Medium and smaller rivers are said to be able to withstand normal floods (Ministry of Water Resources, the People’s Republic of China). As a result, China is better protected against the truly catastrophic floods of the past; however, flooding is increasing along the smaller rivers and lakes because of China’s increasing population, whereby urbanization without strict land management continues to cause significant flood losses.

Exposure at Risk

China has a diverse commercial/industrial building stock, which continues to change as older structures are replaced with ones that are engineered for wind and water resistance. Commercial and industrial buildings are generally more resistant to wind and water damage than residential buildings. Residential wood-frame building is expected to sustain more damage than a residential masonry building. Concrete construction is less vulnerable to flood than steel or masonry. Commercial and apartment buildings usually have stronger foundations than residential buildings, and are thus better able to resist flood loads. Flood vulnerability also varies by building height. Because damage is usually limited to the lower stories of a building, high-rise buildings will experience a lower damage ratio—the ratio of the repair cost and the total replacement value of the building—than low-rise buildings because a smaller proportion of the building is affected. The flooding is also expected to take its toll on agriculture. As of today, July 23, the crop area affected in Hebei province (the neighbor to Beijing) is 132,730 hectares; the total damaged area is 12,540 hectares. While crop insurance is now offered across all provinces and for many crop types, participation remains relatively low because many challenges remain in the pricing and administration of insurance products and in effective risk diversification.

Forecast

Today, Monday, the worst of the rainfall appears to have passed. The Beijing’s airport is operating normally; traffic has also resumed to normal. Even so, hard-hit areas were still feeling the effects of the weekend’s floods; local residents in Qinglonghu, for example, had not returned to their homes for fear they would collapse. Losses from this storm would have been greater had the soils been fully saturated. Should another storm hit this area soon, the soil’s inability to absorb water could become a serious issue. AIR will continue to monitor the situation and will provide updates if warranted.

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Posting Date: July 24, 2012, 5:00:00 AM