I don't see how this could be a waterfall. There is a finished riverbed with dirt right below it, suggesting water won't be flowing into the river from here. Above the wooden structure, there is no bridge for the railroad. Most importantly, the rockwork is practically done. I can't imagine at this late stage they'd pour more concrete, erect more steel, and install more scaffolding. My best guess is these are temporary, to be used during landscaping.