The formation section in the braided river Wikipedia says that very erodible soil causes braided rivers. Intuitively, a rising mountain range like the Pamirs would not be easily erodible.
The Yarkant changes so abruptly, I'm curious what special geological feature is at these straight/meandering-to-braided junctions.
The critical factor that determines whether a stream will meander or braid is bank erodibility. A stream with cohesive banks that are resistant to erosion will form narrow, deep, meandering channels, whereas a stream with highly erodible banks will form wide, shallow channels, inhibiting helical flow and resulting in the formation of braided channels.
Braid 1
Here's near the edge of the Pamir range.
Braid 2
Here's another braided section in the Pamirs, far upstream.
A source
There appears to be a glacier at a source of the Yarkant in Central Karakoram Park. If glaciers present/past explain braiding, why is it intermittent?
Minimal braiding in the Rockies
Mountainous braided rivers seem rare/mild elsewhere, like here in the Rockies in Missoula.