beach erosion vs wearing away

beach erosion and wearing away both are nouns.

Word	Noun	Adjective	Verb	Adverb
beach erosion	Yes	No	No	No
wearing away	Yes	No	No	No

As nouns, wearing away is a hypernym of beach erosion; that is, wearing away is a word with a broader meaning than beach erosion:

beach erosion: the erosion of beaches
wearing away: (geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively

Other hypernyms of beach erosion include eating away, eroding, erosion, wearing.

beach erosion (noun)	wearing away (noun)
the erosion of beaches	(geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively