When an ice run flows to a frozen section, it can become blocked. If the blockage persists, water levels may rise and cause floods and dam bursts, threatening lives and property.

At least half of the buildings in Dujiangyiang will need rebuilding and the dam there is a big potential problem too - if it bursts, our sanctuary down river will be flooded within minutes.

And when the dam bursts, all you can do is swim.