What term refers to the average of all high tides over a period of 18.6 years used as a boundary for submerged and upland properties?

The term that refers to the average of all high tides over a period of 18.6 years is "Mean High Tide." This concept is essential in surveying and property delineation, particularly in coastal areas. It serves as a critical boundary reference between submerged lands (below the Mean High Tide) and uplands (above the Mean High Tide). The 18.6-year period is significant because it accounts for the variations in tidal patterns due to astronomical influences, providing a comprehensive view of tidal behavior over time.

Understanding Mean High Tide is crucial for landowners, surveyors, and legal professionals involved in property disputes or coastal management, as it helps determine property rights and responsibilities concerning erosion, accretion, and land use. The other terms do not effectively capture this specific average over a lengthy duration or their role in defining property boundaries.