We were there in May of '12 and the water was high, there had been a lot of rain. We went up the Holston a short distance (maybe a mile) to anchor for the evening. We had plenty of depth, I don't remember details. Its a pretty river with many waterfront homes. We found a pleasant anchorage and settled in for the night with plans to explore further in the morning. Right after dark we noticed a marked increase in the current. Our anchor held and we let out as much scope as we could. We came to realize that water was being released from a flood control dam upstream. It was a rather sleepless night, and we went back to the Tennessee in the morning.
We also drove along the Holston this spring and I noticed that is is unnavigable further upstream, but I didn't have much of an idea where I was.
We tend to go as far as we can in our exploring and often find interesting places.
I doubt you will experience the dam release and if you keep your eye on the river and the depth you might have an interesting journey.
We did not go up the French Broad.
If you do travel up the Holston or French Broad let us know what you find.
Bruce
Carpy