Rocks in the Rockies?
If you look closely a little above the river shore, you can see a line of rocks. These long runs of piled up rock are commonly seen along Rocky Mountain streams. To me, they were very strange and mysterious for a long time. It never occurred to me that they were done with dredges. Many of the streams involved are not much wider than what you could jump across. It turns out that back in the placer mining days, huge dredges were packed in, a piece at a time, and assembled on site. They would then make their own dam and reservoir. After dredging a site and making the mysterious piles, they move the dam downstream in successive steps, mining as they go. One such dredge still floats in the impoundment at Breckenridge. It's large enough to accomodate The Dredge Restaurant. Very good food, and for me the solution to the mystery.