The river level shows 712.75, according to the web page - that's the lowest ever minus the 701.00 recording from 01-01-1950. Is it possible the record is related to too much revelry the night prior? Just thinking it wasn't read by a computer back then.
I think the river back then had a deeper channel running through the middle, and was dredged years before that to keep a channel open for traffic. As of right now, most of the areas in the river are less then 2 feet deep, except your deeper holes. There is not a chance it will ever drop another 10 feet. Today, the silt has filled in the main channel with many feet of sand, and has widened more then double in most areas.