alluvial

adj

1. (not-comparable)Pertaining to the soil deposited by a stream.

   “I am a working engineer from the Mount Magdalena district of Coolgardie. I don't want to take up your time with outside details so I will only say that about two years ago I had an opportunity of acquiring a share in a very promising claim—gold, you understand, both reef and alluvial.”

   “Soils are a prominent feature of floodplain environments, and we include them in this section because most of the available information on ancient soils pertains to alluvial examples, aside from those in Quaternary-Recent time.”

noun

1. (countable)A deposition of sediment over a long period of time by a river; an alluvial layer.
2. (countable, uncountable)Alluvial soil; specifically, in Australia, gold-bearing alluvial soil.