Yup. Indeed. A group I'm part of had a fatality in a canoe race back in 1991 because of exactly this. It happened in a channelized stretch of river where the dam stretched wall to wall.
The vertical eddy is called a "keeper" around here. The way to escape? Swim to the bottom of the river. Totally counterintuitive and hard in a panic situation.
His death led to some legislation here in Massachusetts about inspecting, marking, and, where feasible, removing these "roll dams."
It also led to race judges making sure racers do the portage and don't try to shoot the dam to save a few minutes.
The vertical eddy is called a "keeper" around here. The way to escape? Swim to the bottom of the river. Totally counterintuitive and hard in a panic situation.
His death led to some legislation here in Massachusetts about inspecting, marking, and, where feasible, removing these "roll dams."
It also led to race judges making sure racers do the portage and don't try to shoot the dam to save a few minutes.