accretion
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 over time and 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.