Many have. Beavers get washed away all the time.

Erosion say this word. Look it up. Tell me is there more erosion or less erosion by water going over the top? It gets heat and it freezes on the surface in weather as well.

Conceptually how do dams work? By letting the water flow over them?

The gulags mined, they felled trees, they made roads and railroads. These transport the food, make the tractors. Yes? Come on. You're not very funny.