Thawing ice triggers Yellow River flood

Published: Tuesday 15 April 2008

The Yellow River: Disaster wai (Credit: REUTERS)More than 13,000 people were evacuated after sections of the main embankment of China's Yellow River collapsed on March 19. The collapse occurred along the river's southern bank in Ordos city in the Inner Mongolia Autonomous Region.

A 450-metre stretch of the embankment first crumbled in the evening, leading to an immediate evacuation of people from six villages. Another 30-metre section of the embankment collapsed the next morning, Niu Shaoyun, deputy director of the flood control headquarters in Hangji Banner, Ordos city, told the state media Xinhua. "About 40 km of the embankment is in danger of further erosion as the river level continues to rise by nearly five centimetres an hour," said Niu. As on March 20, icy waters were flowing through the breaches at 1,450 cubic metres per second, and some other sections of the embankment were holding water at dangerous levels.

About 210 km of the 720 km-long Yellow River in Inner Mongolia began to melt on March 11, after a full thawing of the upper stretch in Ningxia Hui Autonomous Region. To alleviate the flood caused by ice blockage, authorities diverted water from the river through a drainage canal to the nearby Wuliangsu Lake on March 10. Chinese artillery troops also blasted the Qingshuihe section, downstream of the collapsed section, to clear accumulating ice blocks. However, as the river continued to thaw, poorly maintained dams in the region worsened the situation.

Floods resulting from ice thaws are regular phenomena in China. When an ice run flows into a frozen section, it gets blocked. If the blockage persists, water levels rise and cause flooding and dams burst. This year, however, the river's ice flow is the heaviest in 40 years. The watercourse in the region currently holds 50 per cent more water than a normal year. Authorities say ice thawing, which generally finished by the end of January, might continue beyond March. They blame it on the worst snow storms in China this year, which brought rain, sleet and wet snow, with temperatures dipping below -140C. Now that the snow has started melting rapidly, China might experience the worst floods resulting from ice thaw.

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