alluvial sediment vs alluvium

alluvial sediment and alluvium both are nouns.

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

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

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

Other synonyms of alluvial sediment include alluvial deposit, alluvion.

alluvial sediment (noun)	alluvium (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