The hook
Where land touches water — or where the public's right meets the private's — boundaries follow rules that are centuries older than the country itself. Riparian rights along rivers, littoral rights along oceans and lakes, sovereign land grants to the states, eminent domain. These show up on the PS exam and in real practice constantly.
Memorize these
Concepts that show up on the exam
Riparian rights
Rights of an owner whose land borders a flowing watercourse (river, stream). Includes access, use of water, and ownership to the OHWM (or the thread, depending on navigability).
Littoral rights
Rights of an owner whose land borders a non-flowing body of water (lake, ocean, large pond). Same general concept as riparian but the seaward bound is typically the OHWM or mean high tide.
Navigable waters
Waterways usable by commerce. Bed is owned by the STATE (sovereign land). Private ownership stops at the OHWM. Federal courts decide what's navigable for commerce purposes; states may have broader definitions.
Non-navigable waters
Smaller streams not used in commerce. Riparian owners often own the bed to the thread of stream (centerline). State law varies.
Ordinary high water mark (OHWM)
The line on the bank that the water reaches at its ordinary high stage. Identifiable by physical evidence: vegetation, soil characteristics, debris line.
Accretion / reliction
Slow, imperceptible addition of land by water (accretion = soil deposit; reliction = water recession). The riparian owner gets the new land.
Avulsion
Sudden, perceptible change in a watercourse — a flood cuts a new channel. Boundaries DON'T move with avulsion. The original boundary line stays where it was.
Sovereign rights
Powers retained by the government in land that was originally federal/state-owned: navigable water beds, tidelands, public roads, eminent domain.
Eminent domain
Government power to take private property for public use upon payment of just compensation. Surveyor often hired to define the take area.
| Change in watercourse | Type | Effect on boundary |
|---|---|---|
| River slowly deposits silt over decades | Accretion | Riparian owner gains the new land — boundary follows the water |
| Lake gradually recedes | Reliction | Riparian owner gains the exposed bed — boundary follows |
| Flood suddenly cuts a new channel | Avulsion | Boundary STAYS at the old water line — does NOT follow the new course |
| Owner intentionally fills the streambed | Artificial | No transfer of ownership — the bed remains state-owned (if navigable) |
Try it before you peek
Worked example
The problem
A landowner's deed describes the eastern boundary as "thence northerly along the west bank of the Smith River." Over the past 50 years, the river has slowly migrated 30 feet east through accretion. A 2024 flood then cut a new channel 80 feet WEST of the original location, abandoning the old riverbed. Where is the eastern boundary today?
Don't fall for these
What trips people up
Assuming "to the river" means the centerline
Whether the boundary stops at the OHWM or extends to the thread of stream depends on NAVIGABILITY. Navigable → OHWM (bed is state-owned). Non-navigable → often to the thread. State law varies — research the specific watercourse.
Treating slow + sudden the same
Accretion (slow) MOVES boundaries; avulsion (sudden) does NOT. A surveyor who applies the wrong rule will hand a parcel several acres of land that doesn't belong to it.
Forgetting the public trust doctrine
Even in states where private owners hold to the OHWM, the PUBLIC retains rights to navigation, fishing, and recreation in the water itself. A "no trespassing" sign on the riverbank doesn't bar passage on the water.
Test yourself
How well did it stick?
A quick 5-question check on Common Law Boundary Principles. See where you stand and what to review.