stormwater drain vs storm drain

stormwater drain and storm drain both are nouns.

Word	Noun	Adjective	Verb	Adverb
stormwater drain	Yes	No	No	No
storm drain	Yes	No	No	No

As nouns, stormwater drain and storm drain are synonyms defined as:

stormwater drain and storm drain: a system of watercourses or drains for carrying off excess water

Other synonyms of stormwater drain include drain system, drainage well, storm sewer.

stormwater drain (noun)	storm drain (noun)
a system of watercourses or drains for carrying off excess water	a system of watercourses or drains for carrying off excess water