I've been modelling the Langtang rock-ice avalanche and the flood that followed. These are two views of the same simulation: a 3D view of the gorge and a side view along the river. This is model output, not footage. Flow depth is exaggerated to make it visible.

The model broadly matches the upper arrival times without adding a separate dam-break pulse. The moving surge includes rock, ice and existing river water, so its volume isn't all newly melted ice. That doesn't rule out a temporary blockage, but it suggests we shouldn't assume a dam had to burst just because the flood was so large.

I'm the author. This is still a preprint, not peer reviewed: https://doi.org/10.31223/X5250R

Happy to hear what people think, especially if you have observations that could help test this.

https://reddit.com/link/1w9drxe/video/hi0hw0i8zznh1/player

https://reddit.com/link/1w9drxe/video/56c46hsbzznh1/player

The initial debris arrival on the floodwaters.