China Quake Lake Floods Beichuan, Town Must Relocate (quake update 10)

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China Quake Lake Floods Beichuan, Town Must Relocate (quake update 10)

Agriculture Development Bank of China branch in Beichuan after earthquake

photo: unknown via Wikipedia

More than 80% of buildings in Beichuan were badly damaged during the earthquake on May 12, including this bank. Extensive damage and recent flooding from the Tangjiashan quake lake forced Beichuan residents to abandon their town. Chinese officials plan to rebuild the city in another location.

ABANDONED TOWN: Chinese troops blasted through the earthen dam holding back water on the Tangjiashan quake lake. Although pressure was relieved, the lake continued to fill faster than it drained and flooded Beichuan.

by Thea Deley
Informify Staff Writer
June 11, 2008

The government had already evacuated Beichuan, a town so damaged by the May 12 quake that residents must now abandon it. Meanwhile aftershocks continued to shake the region.

Sichuan Earthquake: Quick Facts

Quake Hit:		May 12, 2008
Magnitude:		7.9 (USGS)
Recent Aftershocks:		5.0 (June 8), 5.0 (June 9)
# Confirmed Dead:		69,142
# Still Missing:		17,551
# Left Homeless:		5.2 million
# Threatened by Quake Lakes:		1 million
# Evacuated From Quake Lake Areas:		250,000
Rate Water Filling Tangjiashan Quake Lake		1.8 million gallons/minute

Tangjiashan Quake Lake Floods Beichuan

Water from the Tangjiashan quake lake broke free from its makeshift dam and flooded Beichuan Tuesday. The government had evacuated residents last week just in case.

Chinese troops worked for almost a week, digging and blasting through rocks and mud that blocked the Jianjiang River and formed the lake. They hoped to divert the water through two drainage channels.

Soldiers broke the debris dam Monday night when they set off two large blasts Monday night. At first, the lake's water level fell 40 feet. But water continued to flow into the lake faster than it drained:

Water flowed in at 1.8 million gallons/minute
Water drained out at 792,500 gallons/minute

Soon afterward, the rushing water widened the drainage channels and caused the top of the dam to crack. Soldiers and engineers had to be rescued by helicopter.

The sudden rush of water flooded Beichuan as former residents, soldiers and volunteers watched from higher ground.

Residents Must Abandon Beichuan

The May 12 earthquake damaged the town of Beichuan more than almost any other city:

15,000 people died
80% of buildings collapsed or irreparably damaged

The Chinese government told Beichuan residents they must abandon their destroyed and unsafe town. They hope to rebuild it somewhere else.

Aftershocks...Still

Both Sunday and Monday 5.0-magnitude aftershocks shook the region around Tangjiashan lake. Chinese authorities said the aftershocks didn't rupture the lake's barrier, however.

Question for Readers:

Do you think the Chinese government is doing the right thing by forcing Beichuan residents to abandon their town and rebuild elsewhere?

Tangjiashan is one of 30 "quake lakes" around Sichuan province. Last month's earthquake created the lakes:

Rocks, mud and debris shook loose and fell into the Jianjiang River.
These landslides formed a barrier that dammed the river.
Water continued to flow into the dammed area from the river and rain.
The river flooded its banks and formed a lake.
Water continues to flow into the lake, building tremendous pressure on the makeshift earthen dam, and threatening to burst through and flood the valley below.

Aftershocks threaten swollen China 'quake lake' (Reuters, 6/9/08)

Quake lake drains into ruined Chinese town (International Herald Tribune, 6/10/08)