Wearing away: Falls of Foyers

These are the lower Falls of Foyers by Loch Ness. I was struck on my previous visit by the V-shaped notch at the top of the falls. The total height of the waterfall is given as 62 metres. It's hard to photograph the whole thing. I think that the notch must be about 20 metres deep. I have reasoned that water cannot have flowed down here until after the last Ice Age given that glaciers must have been carving the edges of the Great Glen at that point. So water can only have been flowing this way for about 10000 years. 20000mm divided by 10000 years would mean a rate of attrition of 2mm per year. That's not unreasonable.
The falls really impressed a visiting Robert Burns who wrote a poem on the spot: