High end is a WAG, you could probably go as high as you wanted to.
A house very near the river on river-right provides a good 'way marker', indicating you are nearing the 3-mile mark on this run.
The river will swing left (to head northwest), then sharply right (east), and again left (northwest). This is followed by about a 1.5 mile 'loop' known as Gould Bend. It is roughly in this vicinity that the three main drops (which may merit scouting and/or portaging) exist.