Legal Definitions - mean high tide

The term mean high tide refers to the average height of all high tides observed over a specific, long-term period, typically 18.6 years. This measurement establishes a consistent and legally recognized line along coastlines and tidal waterways. It serves as a crucial reference point for defining property boundaries, regulatory jurisdiction, and the demarcation between private land and public trust lands (such as submerged lands or tidelands). Essentially, it represents the average boundary where the sea typically meets the land at its highest point.

• Example 1: Defining Coastal Property Boundaries

  Imagine a homeowner who owns a piece of land along the oceanfront. When the property was surveyed and legally described, its seaward boundary was specified as the mean high tide line. This means that while the water level fluctuates daily with the tides, the legal edge of their private property is not the highest point the water ever reaches, nor the lowest, but rather the calculated average of all high tides over nearly two decades.

  How it illustrates the term: This example shows how mean high tide provides a stable, legally recognized boundary for private property. It prevents the property owner from claiming land that is regularly submerged by the average high tide and ensures that public access rights, which often extend to this line, are preserved.

• Example 2: Environmental Regulation and Permitting

  A developer plans to construct a new pier extending into a bay. Before construction can begin, they must obtain permits from state and federal environmental agencies. These agencies often have jurisdiction over "navigable waters" and "wetlands," which are frequently defined as areas seaward of or regularly inundated by the mean high tide line. The agencies will use this specific line to determine the extent of their regulatory authority and whether the proposed pier will impact public resources or protected habitats.

  How it illustrates the term: Here, mean high tide acts as a jurisdictional marker. It defines the geographical scope within which environmental laws and regulations apply, ensuring that development in sensitive coastal areas is properly reviewed and managed to protect public trust resources.

• Example 3: Public Access Rights to Beaches

  In many coastal states, the public has a right to walk along the wet sand area of beaches, even if the adjacent dry sand is privately owned. This public access right often extends up to the mean high tide line. If a group of beachgoers is walking along the shoreline, they are generally considered to be on public land as long as they remain below this average high water mark, regardless of whether the tide is currently high or low.

  How it illustrates the term: This example demonstrates how mean high tide clarifies the boundary between private property and public access areas. It provides a consistent reference point for where the public's right to traverse the beach begins, even though the actual water line changes throughout the day.