What are China's 'quake lakes" and why are they dangerous?

Question

What are China's 'quake lakes" and why are they dangerous?

Answer 1

tons of rocks and soil falling down from mountain during mudslide due to the quake underneath, gradually accummulate and block the original  riverbed. Quake lakes(reservoire) therefore take into shape.

With more water from upperstream coming into the reservoire, villages nearby can be submerged. The daily increase is about 1.5meters. The solution to this is to clear the riverbed, free of blocks. Locals need to be transferred too.