1 In property law, the gradual increase in land through natural processes; for example, the creation of land caused by the deposit of sediment on a shoreline of a river or ocean. The new land becomes the property of the owner of the property to which it is attached. See also alluvion, reliction, and avulsion. 2In succession law, the increase in an heir or legatee's interest in property when a co-heir or co-legatee dies before the property vests, rejects his inheritance or legacy, fails to com...