Wife and I visited when the American falls were shut off.  We walked on the rocks that usually were pounded by water when the falls were wet.  Thing I remember was they had many lawn sprinklers keeping the face of the falls, keeping the rocks wet while no water was tumbling over the edge.

We didn't know it was happening when we left, were disappointed at first, then realized we could see something not many would see for many years, and enjoyed our visit.  Went back twenty years later to see both falls operating normally.