[Fraxinus]

I suppose braided streams only occur when the water is able to cut through the soil because nothing holds it together or when it is rushing through with such force it simply uproots all vegetation in its way.

My understanding of such things is that a Braided stream is a sign of a depositing stream. The braided pattern is independant of vegetation. Alluvial fans in the west have braided stream beds, these occour where the run-off reaches soil (as opposed to rock) and can seep in reducing the volume of the flow and the carrying capacity of the stream. Most of the rivers crossing the great plains once had braided streams.

[stormer]

Geomorphologists call the braiding “anastomosis” (not to be confused with the medical term). It is strong evidence of flood or flashiness (large variation in discharge) in streams. The pattern is common in rivers whose source freezes in the winter and then releases it water in a well defined event. Arctic rivers and those feed by glaciers often show this type of pattern where (primarily) gravels are redistributed (smaller material is washed away). The Scablands of eastern Washington (as seen the satellite photos someone posted earlier) are off the scale examples of these. First identified by a fellow named J Harlan Bretz as evidence of flooding, he was laughed off because nobody believed you could have a flood that big, and he was unable to provide a mechanism for it. It was only after aerial photographs became available and evidence from ancient lake shores in Montana indicated he was right all along.