"Tim" wrote
I'm sure blue water boating , flares would be
really convenient, that is, if not a necessity. But would such be
really needed for running rivers?

They aren't required equipment for us river runners. You could maybe try to
use a flare if you find yourself dead in the water mid channel at night with
a barge bearing down, but you're probably a lot better off deliberately
avoiding finding yourself in that position in the first place.