I wonder if use of flumes to construct rapids to drive turbines would be less environmentally damaging than dam construction. I'm way out of my field of expertise here, but that's one reason I started this blog. That is so I can ask stupid, but hopefully ultimately instructive questions. Anyway, it seems to me that beside the drowning of large areas, that Dams also seriously influence downstream transport of suspended sediments. This can have dire consequences for many riverine systems and associated fringing ecosystems and deltas (see for example issues surrounding the Narmada River in India. But what if we just diverted part of the river to a series of large flumes that created rapids sufficient to drive turbines? Seems that this would have less of an impact on sediment transport. I realize that these might be somewhat less efficient, but that could be largely overcome by building more of them. It might help out many of our anadromous fishes too.