here. And there is a second video here that shows how the floodwater entered the Colorado as a foamy mess. These are amazing images. I have heard estimates that National Canyon had a peak flow of about 15,000 cubic feet per second, making it almost as large as the Colorado River on that day.
here. I have heard no estimates of the discharge on this flood but it is quite a bit smaller that what came down National. Anyone who would have been caught in the narrows in Fern Glen Canyon however, would not have cared one bit if this flood was somewhat smaller - the amount of runoff is impressive and deadly.
Flash floods are common in landscapes that contain widespread bare rock exposures with few soils. They are the mechanism by which the canyons are created and facilitate the deep dissection that makes the Colorado Plateau and Grand Canyon so wonderful. With the advent of cheap but high quality electronics, more of these events are now visible to us. Watching the majesty and power of these events stirs the soul.
Addendum - 12/12/12: I became aware of this footage of the Red Canyon flood at Hance Rapid today! Here it is.