The problem becomes one of how spread out the energy is.

Sure the water in that creek might be falling hundreds of meters, or even kilometers, but without a dam the height differential at your generator is only going to he a few metres at best. Enough to power the lighting, fridge, and washing machine in the houses that the creeks happen to run by, but not much else.

With the advent of long lasting perovskites and (hopefully) some less polluting battery technologies you're not even better off cost-wise.

You might be able to do something with a long pipe parallel to the creek to get more head, but then you're going to spend a lot of your energy on wall friction unless it's very wide.