Two men can chop down even a thick, sturdy rosewood tree in an hour. Then it requires teams of 15 or 30 or 50 to pull the logs through the muddy up-and-down of the vine-covered woodland.

The recent rain had churned up the waterfall into a muddy whirlpool.

Where 50-kilogram king salmon once fought their way up waterfalls to lay their eggs in gravel beds, there now are only concrete walls holding back still water and deep beds of muddy deposits.