Quick post here 'cause I'm terribly curious about this story, link sent by Capt. J.P.
Low-head dams are frequently called (at least by those in the know) as "drowning machines". A full technical description can be found in reports like this.
When I saw that article, the first thing that sprang to mind was "I wonder if a spillway like that might feature the same sort of hydraulics".
E.B. Klassen at Kayak Yak has now posted some pictures showing the bottom of the spillway and I am seriously wondering if there are any whitewater-savvy people who might be able to look at that & weigh in as to whether that was just silly, or flat-out dangerous.
I'm not usually one to jump on the "What a bunch of idiots" bandwagon, but that looks, to my non-whitewater-trained eye, like that might have been pretty hazardous.