PS Boundary Law & Riparian Rights 2 — Questions and Answers
Question 1: Under the doctrine of accretion, who owns land gradually deposited by a river along a riparian owner's bank?
- The state government
- The riparian landowner (Correct answer)
- The adjacent upstream owner
- The federal government
Correct answer: The riparian landowner
Under accretion, land gradually and imperceptibly added to a riparian owner's bank by water action becomes the property of that riparian owner.
Question 2: When a river suddenly changes course due to a flood, cutting off a parcel, this event is legally known as:
- Accretion
- Reliction
- Avulsion (Correct answer)
- Erosion
Correct answer: Avulsion
Avulsion is the sudden, perceptible shift of a watercourse, and under avulsion doctrine the boundary remains at the old channel location.
Question 3: The term 'reliction' in boundary law refers to:
- A river changing course overnight
- Land exposed by the permanent withdrawal of water (Correct answer)
- The gradual deposit of sediment
- A court-ordered boundary reestablishment
Correct answer: Land exposed by the permanent withdrawal of water
Reliction (or dereliction) is the gradual recession of water that permanently exposes new land, which accrues to the adjacent riparian owner.
Question 4: In the prior appropriation doctrine used in western US states, water rights are based on:
- Ownership of land adjacent to the water
- First in time, first in right (Correct answer)
- Equal sharing among all users
- Federal allocation by the Bureau of Reclamation
Correct answer: First in time, first in right
Prior appropriation allocates water rights by priority of use — the first person to put water to beneficial use holds senior rights over later appropriators.
Question 5: A navigable river serves as a boundary between two states. The boundary line is most commonly located at:
- The low-water mark on either bank
- The thread of the stream (thalweg) (Correct answer)
- The high-water mark on either bank
- The center of the river measured horizontally
Correct answer: The thread of the stream (thalweg)
For navigable interstate rivers, the boundary is typically the thalweg — the line following the deepest channel or main navigable channel.
Question 6: Under common law riparian doctrine, a landowner whose property borders a non-navigable stream owns to:
- The high-water mark on the near bank only
- The low-water mark on the near bank only
- The center thread of the stream (ad medium filum aquae) (Correct answer)
- Only the land above the ordinary high-water mark
Correct answer: The center thread of the stream (ad medium filum aquae)
At common law, adjacent owners of a non-navigable stream each own to the center thread of the stream (ad medium filum aquae), subject to the other owner's equal rights.
Question 7: Which of the following best describes the 'ordinary high-water mark' as used in defining public vs. private ownership of tidal lands?
- The highest tide ever recorded at that location
- The line reached by the average of all high tides (Correct answer)
- The line reached by the mean high water of spring tides
- The line of vegetation marking the upper beach
Correct answer: The line reached by the average of all high tides
The ordinary high-water mark is established by the average (mean) of all high tides over a 19-year tidal epoch, not just spring or extreme tides.
PS Boundary Law & Riparian Rights 2
Under the doctrine of accretion, who owns land gradually deposited by a river along a riparian owner's bank?