We didn’t want to run the spillway, but
we were deterred by no-trespassing signs on the portage route. This would eventually be a pretty big concrete and earth fill dam, but when we arrived, the spillway had not been closed, and the river was running through the four gates.
I crept close to the edge in my c-1, and it looked like clear runout. What should have warned me off was that the haystacks in the runout were rather small, suggesting that something [the hole] was slowing the water.
Once I was committed to the drop, I saw the backwash of the hole, which was about as wide as the length of my boat. Fortunately for me, the C-1 submarined (I could feel it scrape bottom), and by getting the boat cocked toward my paddle side, I was able to drag it free with a series of hard strokes.
The guy behind me, in a Blue Hole with a truck tube for flotation, apparently did not appreciate my difficulty, because he came on through. The backwash stopped and turned his bow, and then for many anxious minutes, it was Maytag time. He slipped out, and later his truck tube came loose and the boat endered out.
This spillway was NOT as difficult as the low head dams I have seen.