Alluviation is the gradual shifting of land boundaries caused by the depositing of gravel and sediment by a moving body of water. Alluvion is the actual sediment deposited on the land (e.g. a bank or shore). Under common law, land altered by alluviation is typically considered to change any boundaries originally determined by the body of water, thereby increasing the owner’s property. In the 1836 Supreme Court case of The Mayor, Alderman and Inhabitants of New Orleans v. The United States, the Court held that while a landowner obtains land increased by alluviation, they can also lose land decreased by alluviation.
[Last updated in June of 2021 by the Wex Definitions Team]