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Wed, May 03, 2000 - Page 2 News List

COA makes risky move in tackling barrier lakes

ENVIRONMENT Officials have alleviated pressure on one landslide dam lake that threatens to burst, but some Nantou County residents fear the excavation work will just increase the threat further downstream

By Chiu Yu-Tzu  /  STAFF REPORTER

Tuan Chin-hao, a professor of water resources at National Chung-hsing University, uses an aerial photograph to explain why a water channel was excavated between two barrier lakes in Nantou County. The lakes, formed during the 921 earthquake, are close to bursting their banks after recent rains, imperiling residents downstream.

PHOTO: LIN YOU-HUA, LIBERTY TIMES

Government officials yesterday took action to prevent a potential disaster in Nantou County posed by barrier lakes formed after last year's 921 earthquake.

The officials ordered the excavation of a shortcut waterway between two bodies of water that have built up behind temporary dams caused by mudslides, and which threaten to burst and release a torrent of water downstream.

Local residents, however, have criticized the sudden action as a careless strategy, whose consequences could have grave implications for their safety.

Officials from the Council of Agriculture's (COA) Soil and Water Conservation Bureau (水土保持局) were joined yesterday by academics in an inspection of the two barrier lakes, formed near Chiufenerh Mountain (九份二山), where the epicenter of the 921 quake was located.

Suspecting that torrential rainfall in central Taiwan has undermined the geological structure of nearby mountainous areas, officials made a crucial decision to dig a 30-meter-long waterway between the upper and lower lakes. A bulldozer was used to push debris, rock and mud aside, while other earthmoving equipment dug a channel in which to contain the water flow.

Officials said the temporary waterway would channel excess accumulated water in one of the lakes in the upper reaches of the Chiutsaihu River (韭菜湖溪) to the other, located along the Shetzuken River (澀子坑溪).

"We are digging slowly in order to keep the [water] system stable," said Tuan Chin-hao (段錦浩), a water resource professor at National Chung-hsing University.

"We are attending to the upper lake first because of its obvious instability. The upper lake is only 400 meters wide, while the lower one is 700 meters," Tuan said.

"The pressure on the banks of the lake can be reduced by making the lake shallower," said Li Kuo-cheng (李國正), Tuan's assistant, adding that the lower the water level, the less the threat of mudflows further downstream.

In addition to the water channel, fortifications built earlier by COA officials to prevent overflowing included dumping rocks along the lakes' edge to reinforce it, and building temporary earth dams.

However, residents criticized the actions carried out yesterday, saying it could endanger those living downstream.

"We're afraid that mudflows and landslides will be triggered by rising water in the lower lake," said Luo, a resident who pointed out that both the width and depth of the shortcut channel were increasing.

"What are we supposed to do if the lower lake collapses?" Luo said, citing concerns it may overflow because officials had apparently never thought of expanding the pipe that drains the lower lake.

Residents said that forecasts for continued rain issued yesterday by the Central Weather Bureau continue to present threats of further landslides.

Responding to pleas for help from residents, several legislators criticized the central government yesterday at a public hearing in Taipei. They said people living in the path of potential mudflows are being ignored as the central government prepares for its transfer of power.

"Chiufenerh Mountain is home to only one of more than 1,000 threatened communities in Nantou County," said DPP legislator Tsai Huang-liang (蔡煌瑯) from Nantou County, urging authorities not to neglect the peril.

"The priorities for the government are to evacuate more people and stockpile necessary goods for any refugees," said DPP legislator Lee Chun-yee (李俊毅).

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