flowage vs filling

flowage and filling both are nouns.

Word	Noun	Adjective	Verb	Adverb
flowage	Yes	No	No	No
filling	Yes	No	No	No

As nouns, filling is a hypernym of flowage; that is, filling is a word with a broader meaning than flowage:

flowage (noun)	filling (noun)
the act of flooding; filling to overflowing	the act of filling something
a body of water that has been created by deliberately flooding an area	the yarn woven across the warp yarn in weaving
gradual internal motion or deformation of a solid body (as by heat)	(dentistry) a dental appliance consisting of any of various substances (as metal or plastic) inserted into a prepared cavity in a tooth
	a food mixture used to fill pastry or sandwiches etc.
	flow into something (as a container)
	any material that fills a space or container