Riñihuazo

During the Great Chilean earthquake, several landslides near Tralcán Mountain blocked the outflow of Riñihue Lake at (39°46′43″S 72°27′03″W / 39.77861°S 72.45083°W / -39.77861; -72.45083).

The blocked San Pedro River, which drains the lake, passes through several towns and the city of Valdivia before finally reaching Corral Bay.

To avoid the destruction of the city, several military units and hundreds of workers from ENDESA, CORFO, and MOP started an effort, called the Riñihuazo, to control the lake.

Twenty-seven bulldozers were put into service, but they had severe difficulties moving in the mud near the dams, so dykes had to be constructed with shovels.

By 23 May, the main dam had been lowered from 24 to 15 meters, allowing 3 cubic kilometers of water to leave the lake gradually, but still with considerable destructive power.