The Merriam Webster dictionary includes an adjective:
adjective al·lu·vi·al \ə-ˈlü-vē-əl\ geology : made up of or found in the materials that are left by the water of rivers, floods, etc.
noun al·lu·vi·on \ə-ˈlü-vē-ən\
1 : the wash or flow of water against a shore
3 : alluvium
4 : an accession to land by the gradual addition of matter (as by deposit of alluvium) that then belongs to the owner of the land to which it is added; also: the land so added.
and the verb:
verb al·lu·vi·ate \-vēˌāt, usually -ād + V\
: to cover with alluvium <an alluviated valley>
: to deposit alluvium
We would like to interpret is as the process that discovers nuggets of insight from a large body of data. Such as what they did in the old days when they panned for alluvial gold: