This may be one of the best views of really big boulders being floated in a debris flow I have ever seen. The rocks are floated because the specific gravity of the fluid becomes so high due to the presence of greater than 50% by volume of sediment in the flowing fluid. The best part of the film is about one and half minutes into the clip.
The footage is from northern Pakistan and was via Dave's Landslide Blog. Dave had a another video suggestion that I had put up in July on Yosemite thanks to Sam Crawford.
Debris flows a big risk to alluvial fan areas in Washington State and numerous debris flows have routinely damaged property whenever we get big rain falls.