al·lu·vi·um 
(ə-lvē-əm)
(ə-lvē-əm)n. pl. al·lu·vi·ums or al·lu·vi·a (-vē-ə)
Sediment deposited by flowing water, as in a riverbed, flood plain, or delta. Also called alluvion.
[Medieval Latin, flood, from neuter of Latin alluvius, alluvial, from alluere, to wash against; see ALLUVION.]