I don't know much about Cataract, but you might notice that the gage site has a disclaimer reading "Provisional Data Subject to Revision." After a major debris flow/ sedimentation event, the shape of the bottom can change, throwing off the gage calculations. The USGS people go out to re-survey the bottom at each gage on a regular basis, and then recalculate the data as needed. This is according to my husband Mike, who is a hydrologist.
Also, the water seems to act differently when it is so heavily loaded with sediment, especially where swirlies are concerned. Mike says this is due to density currents down below. It can look like "Big Water" even when it isn't.