I guess a bunch of cairns got built near Fayette Station rapid on Bridge Day a couple of weekends ago. There are five in this picture and one in front of the big one that's out of the frame. You can see three of them pretty clear in the background and if you look hard you can spot the fourth one. It'll be interesting to see how they fare the next couple of days. If I had to guess, I'd say they won't do very well.