dam vs dam up

dam is a noun but dam up is not a noun.

Word	Noun	Adjective	Verb	Adverb
dam	Yes	No	Yes	No
dam up	No	No	Yes	No

As verbs, dam and dam up are synonyms defined as:

dam (noun)	dam up (noun)
female parent of an animal especially domestic livestock
a barrier constructed to contain the flow of water or to keep out the sea
a metric unit of length equal to ten meters

dam (verb)	dam up (verb)
obstruct with, or as if with, a dam	obstruct with, or as if with, a dam