Severn River vs river

Severn River and river both are nouns.

Word	Noun	Adjective	Verb	Adverb
Severn River	Yes	No	No	No
river	Yes	No	No	No

Severn River (noun)	river (noun)
a river in England and Wales flowing into the Bristol Channel; the longest river in Great Britain	a large natural stream of water (larger than a creek)
a river in Ontario that flows northeast into Hudson Bay