The dams in the Grand River are classified as low-head dams. Low-head dams have unfortunately earned the nickname of “drowning machines” due to the dangerous recirculation of current that results from the water flowing over the dams and hitting the river bottom. This “keeper hydraulic” is very dangerous and extremely difficult to escape. These dams also span the entire width of the river and the keeper hydraulic captures large woody debris and other material making a dangerous situation even worse. Unfortunately, there have been injuries and deaths as a result of these low-head dams in the Grand River.
For a very technical, but informative explanation of the science behind these dangerous structures, check out this video from Practical Engineering:
Drowning Machine: The Dangers of Low-head Dams