gradual formation of new land, by recession of the sea or deposit of sediment
<noun.process>
the rising of a body of water and its overflowing onto normally dry land
<noun.phenomenon> plains fertilized by annual inundations
clay or silt or gravel carried by rushing streams and deposited where the stream slows down
<noun.object>
Alluvion \Al*lu"vi*on\, n. [F. alluvion, L. alluvio, fr. alluere to wash against; ad + luere, equiv. to lavare, to wash. See {Lave}.] 1. Wash or flow of water against the shore or bank.
2. An overflowing; an inundation; a flood. --Lyell.
3. Matter deposited by an inundation or the action of flowing water; alluvium.
The golden alluvions are there [in California and Australia] spread over a far wider space: they are found not only on the banks of rivers, and in their beds, but are scattered over the surface of vast plains. --R. Cobden.
4. (Law) An accession of land gradually washed to the shore or bank by the flowing of water. See {Accretion}.