alluvium vs alluvial sediment

alluvium and alluvial sediment both are nouns.

Word	Noun	Adjective	Verb	Adverb
alluvium	Yes	No	No	No
alluvial sediment	Yes	No	No	No

As nouns, alluvium and alluvial sediment are synonyms defined as:

alluvium and alluvial sediment: clay or silt or gravel carried by rushing streams and deposited where the stream slows down

Other synonyms of alluvium include alluvial deposit, alluvion.

alluvium (noun)	alluvial sediment (noun)
clay or silt or gravel carried by rushing streams and deposited where the stream slows down	clay or silt or gravel carried by rushing streams and deposited where the stream slows down