First, I should tell you that the rate of recession of the Canadian Horseshoe Falls is caused by the volume of water flowing over them. The more the water that flows over the falls, the more the recession. That’s because the water at the top of the falls wears away the heavy top layer of Dolostone, which eventually falls into the river below.
Prior to the early 50’s and before the diversion of water upriver to be used to create water power(hydro) at plants below the falls at Queenston and Lewiston the flows was much heavier that it is today resulting in a recession rate estimated by some people at 30 centimetres(one foot )per year.
Today half the water that can go over this falls is diverted at all times. During the colder winter months another 25 % is also diverted so only one-quarter flows over all falls. This has resulted in a much slower rate of diversion.
Some articles that I have read say the recession rate is now about 30 centimetres (one foot) in ten years.
Personally I think it a lot less. I’ve been hanging around the falls for the past 60 years and when I look at the brink of the falls at Table Rock I see very little recession. If it did recede 60 feet over these past years we would have had to move this wall backwards many times and Gull Island above the falls most likely would have disappeared. It’s my belief that recession of the Canadian Horseshoe Falls has been about 15 centimetres (6 inches) over the past 60 years.
There is relatively no recession of the American Falls due to the fact only 10 per cent of the water of the upper Niagara River is going over this falls.
All this said I’d like to be able to find someone who could accurately tell me about this recession.