Satellite images of the Beichuan area of Sichuan, released by Taiwan's National Space Organisation in the days after the 12 May earthquake, showed huge landslides.
The river running down from the mountains and through the devastated town of Beichuan was blocked by earth (seen as brown). Roads were covered and buildings swept away.
Blocked rivers formed about 30 lakes in the earthquake zone, like the one illustrated here upstream of Beichuan. Lakes like this pose a serious flood risk to people living downstream. Creating channels to drain the lakes before any flooding can occur is a key task for the Chinese authorities.
Chinese soldiers use missiles and other explosives to open drainage channels
Troops have used explosives and even missiles to blast channels to relieve the water pressure building up in Tangjiashan - the largest of the lakes caused by the earthquake and its aftershocks.
Two "massive blasts" on Monday evening widened a bottleneck in the drainage channel allowing the water to be released.
The water was sent towards the deserted town of Beichuan, prompting authorities to evacuate residents and seal it off. The town is to be rebuilt elsewhere, according to reports.
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