Accretion in law refers usually to the slow addition of land next to water due to the water’s movement or the increase of beneficiary’s share of a trust due to the actions of another beneficiary.
Accretion from natural causes (also referred to as alluvion) adds soil, sand, and other types of earth to the part of a person’s property that borders water. While this occurs very slowly, a piece of property may grow a lot overtime and may increase its value. Any addition to one’s property by accretion becomes that person’s legal property. This is in contrast with avulsion where the original owner of the moved earth continues to own it. Avulsion occurs where large parts of a person's property suddenly moves away due to natural events such as flooding.
Accretion in estates occurs where a beneficiary to a trust receives more than their original share of the trust. Often, this occurs because one of the other beneficiaries does not take their share or does not fulfill a requirement for them to receive their share of the trust.
[Last updated in November of 2021 by the Wex Definitions Team]