Water Boundaries: Riparian and Littoral Rights, Accretion, Reliction, Erosion, and Avulsion
Two vocabularies
Riparian rights attach to land bordering a stream or river; littoral rights attach to land bordering a sea, lake, or pond. In most states, title to the beds of navigable waters passed to the state on equal footing, and the upland owner's boundary is either the ordinary high water mark or the thread (middle) of the stream, depending on state law and navigability. Non-navigable stream beds generally pass to the riparian owner to the thread.
Slow versus sudden change
Accretion is the gradual, imperceptible addition of land by natural action; the boundary moves and the new land belongs to the upland owner without any deed or payment. Reliction (dereliction) is the gradual exposure of bed by receding water and generally follows the same rule. Erosion is gradual loss, and the boundary follows the water. Avulsion is a sudden, perceptible change of channel; the boundary stays where the water was, and the avulsed owner does not gain or lose land. Artificial additions and government channel work usually do not count as accretion.
Meander lines
The meander line is not a boundary. It is a survey line run to compute the area of the fractional upland parcel; the water itself is the boundary unless the description plainly calls a fixed line. This is the single most commonly tested water-boundary trap.
Worked example
A river gradually shifts 60 feet toward a downstream owner over 30 years; that owner loses 60 feet. In year 31 the river jumps a new channel overnight across the upstream neighbor's field. The boundary remains the old channel location; the field does not change ownership. Gradual means move, sudden means stay.
Other traps
Accreted land is not acquired by adverse possession and needs no conveyance. A boundary that follows an ambulatory water line is a moving boundary that can be described by reference to the water, not to a monument.