How much does Niagara Falls erode each year?
Studies to determine how much erosion was taking place were started in 1842. Between that year and 1905 erosion took place at the rate of 1.16 meters, or 3.8 feet per year, at Horseshoe Falls. Between 1906 and 1927 the erosion rate declined to .70 meters, or 2.3 feet per year. The decline was due to water being diverted for hydro electric generation.
Currently remedial efforts are underway to reduce the erosion even more. It is estimated that erosion is reduced to less than 1 foot per year due to those efforts. At American Falls the flow rate of 10,000 cubic feet per second is insufficient to cause any major erosion.
As it stands today, American Falls has an erosion rate of about 3 to 4 inches per year. The biggest factor for the American falls is the fact that it has cracks at the Crestline in the top cap rock layer. Underneath that is a softer shale layer. The lifting action of water coming through these cracks cause them to become larger and along with the freezing and thawing each year, the rock structure continues to weaken until that part finally cracks and falls off. The flow at American Falls isn't strong enough to erode the rocks at the bottom of the Fall.