Legal Definitions - tide

In a legal context, a tide refers to the natural, rhythmic rise and fall of ocean water levels, primarily caused by the gravitational pull of the moon and the sun. This definition specifically excludes changes in water levels caused by temporary factors like strong winds, storms, or seasonal weather patterns. Tides are crucial in law, particularly for determining the boundaries of coastal properties and public access rights along shorelines.

Specific measurements related to tides include:

• Mean High Tide (also known as Ordinary High Tide): This is the average height of all high tides over a specific, extended period, often measured over 18.6 years. It is a critical legal benchmark, frequently used to establish the boundary between privately owned upland property and the publicly owned tidelands or submerged lands.
• Mean Low Tide: This is the average height of all low tides over a fixed period.
• Mean Lower Low Tide: This is the average height of only the lower of the two daily low tides over a fixed period.
• Spring Tide: These are tides that are significantly higher than average (for high tides) or lower than average (for low tides). They occur when the sun, moon, and Earth are nearly aligned during a new moon or full moon, combining their gravitational forces.
• Neap Tide: These are tides that are lower than average (for high tides) or higher than average (for low tides). They occur during the first and last quarter moon phases, when the sun's gravitational pull partially counteracts the moon's, resulting in less extreme tidal ranges.

Examples:

• Coastal Property Boundaries: A homeowner purchases a beachfront lot, and their property deed specifies that the land extends "to the mean high tide line." This legal description means that the private ownership of the land ends at the average point where the high tide reaches. The area seaward of this line, including the wet sand and any submerged land, is typically considered public property. This consistent, legally defined tidal boundary prevents disputes that might arise if the property line were to shift with every unusually high wave or storm surge.

• Environmental Permitting for Coastal Construction: A company plans to construct a new marina. Before construction can begin, they must obtain permits from state and federal environmental agencies. These agencies often use the mean lower low tide line as a critical reference point to determine the extent of submerged lands that will be impacted by the marina's pilings and docks. This ensures that the construction complies with regulations designed to protect marine habitats that are only exposed during the lowest tidal cycles, and to prevent interference with navigation.

• Public Access Rights to Beaches: In many coastal states, the public has a legal right to access the "wet sand" portion of a beach. This right is often defined as the area between the mean high tide line and the water's edge. For instance, during a spring tide, when the high tide reaches exceptionally far up the beach, the visible dry sand area shrinks, but the public's right to access the wet sand remains legally defined by the consistent mean high tide line, regardless of the temporary water level. This ensures that public access is maintained on a predictable basis, not just when the tide is unusually low.