We entered the Au Sable river on several different locations; however, our favorite stretch was the launch at the loud dam and then pull-out at the "whirlpool". The water was crystal clear and teaming with fish especially the salmon. The salmon were making their way up the river to spawn with spectacular leaps. The river varies in flow speed from lazy to approximately five mile per hour.
I would get a map from from one of the ranger stations in Mio or Oscoda which cost $6.00.