I know the Trisuli valley a little. And we've seen these kinds of outburst floods in the Himalayas before, though not this big. That valley is an ancient trade route- the way comes from the Newar city-states (now the Kathmandu conurbation), to Nuwakot on the Trisuli, along up past Betravati to Kyirong, and then on to other parts of Tibet. There were dozens of villages, monasteries, shrines, and markets along there, thousands of years of settlements and rituals and fields and forests.
Sometimes it feels like a slow process - the butterflies diminish year on year, the sea takes away a bit more of the golf course; and sometimes the actual speed of change is made horribly clear.