-snip-
Welp, I walled off an out of place ramp leading out of the river near the falls and my dwarves are no longer interested. The merchants, however, still jump right in the river and walk off of the fall. Some of the animals spend a season or two fighting the current before they're swept away. I'm considering making the river wagon accessible, but I'm not sure I can keep my dwarves away if there is an access point that close to the falls and thus the socks. Nor am I sure about wagons' arrogance towards water. And gravity.
In my first attempt to do this my masons were busy building and, fed up with the situation, I decided to wait and see. 6 dwarves in the span of what was probably 4 seconds. Their deaths were unreasonably clean so I decided to save scum and lost a couple hours of work. After going right to patching the problem area, a child decided he was prepared for the drop. Wall patched and the child still fighting the current, I saved and walked away with a win/win.
Also, I concluded the issue with my dwarves was because I diverted the flow of the river(4 wide) for a moat(2 wide) and led that off the cliff, too, because waterfalls are cool. At the time, I didn't see much of an influence in the flow in the river so I counted myself lucky. Turns out ~4-6 spaces up the river from the fall were influenced enough to keep them filled at 2-4, and a ramp near that area allowed for opportunity during pathing. My dwarves, seeing this opportunity, decided to try to stockpile/eat/wear the goods at the bottom.
The merchants still jump into the river at 7/7 so that's not my problem. Now to work out how to get that loot... Can dwarves scuba if they have the proper swimming skill?