I think you can throw a small hydro electric generator in a river without anybody noticing, and maybe generate a couple 1000 watts. If you want to start building a hydro electric dam that would generate the type of power you are talking about you would 100% need local approval, state approval, and federal approval. Think of a community board, the state assembly, and the EPA. It would take millions of dollars and probably about 5 -10 years to get all of the approvals needed.
Regulation is the Fing best!!!
Alas this.. the gov is the worst.
You can't even collect rain in rain barrels in many places.
Shame solar and wind are so expensive.. They really have made it impossible to create power, on purpose I would assume.