Legal Definitions - mean lower low tide

Mean Lower Low Tide refers to the average height of the lowest daily low tide observed over a specific, long-term period, typically 19 years. In many coastal areas, there are two high tides and two low tides each day. Often, one of these daily low tides is lower than the other. The "lower low tide" is the lower of these two. By averaging these lowest daily low tides over an extended period, scientists and surveyors establish a consistent baseline or datum. This datum is crucial for various purposes, including navigation, coastal engineering, and defining property lines.

• Example 1: Defining Coastal Property Boundaries

  Imagine a homeowner who owns a beautiful beachfront property. The legal boundary of their private land often extends down to the mean lower low tide line. Any land seaward of this line is typically considered public land or subject to public access rights.

  This illustrates how Mean Lower Low Tide serves as a fixed, legally recognized demarcation point, preventing private ownership from extending indefinitely into the ocean and preserving public access to the foreshore.

• Example 2: Nautical Charting and Safe Navigation

  A ship captain is navigating a large cargo vessel into a harbor known for its shallow areas. Nautical charts display water depths relative to the mean lower low tide. This means the depths shown on the chart represent the minimum water depth expected under normal tidal conditions.

  By using Mean Lower Low Tide as the reference, mariners can be confident that the charted depths are generally the shallowest they will encounter, providing a crucial safety margin and helping them avoid running aground, especially during the lowest tides.

• Example 3: Coastal Construction and Infrastructure Planning

  Engineers are designing a new pier for a bustling fishing village. They must consider the mean lower low tide when determining the appropriate foundation depth for the pier pilings and the height of the pier deck. This ensures the structure remains stable and accessible even during the lowest water levels, preventing boats from being stranded or the pier from being unusable.

  This demonstrates how Mean Lower Low Tide is a critical reference for ensuring that coastal infrastructure is built to withstand the full range of tidal fluctuations, preventing damage or inaccessibility during extreme low tides.