I am not sure if this way turns to a river when the heavy rainfall hit the hillside of the mountain or not. Heavy snowfall may carve the hillside but the smell of sulfur indicates that some landslide made this way.
The flow of water or snow that contains sulfur may keep the plants from growing up.
Do you remember the scenery from the peak of Mt. Iwao(nupri)? Strong wind seemed to try to blow us away from the peak on that day.