alluvion

noun

1. Law. a gradual increase of land on a shore or a river bank by the action of water, whether from natural or artificial causes.
2. overflow; flood.
3. Now Rare. alluvium.

noun

1. 1. the wash of the sea or of a river
   2. an overflow or flood
   3. matter deposited as sediment; alluvium
2. law the gradual formation of new land, as by the recession of the sea or deposit of sediment on a riverbed