What does Mean Higher High Water (MHHW) measure?

Mean Higher High Water (MHHW) is used to determine the average height of the higher of the two daily high tides observed over a specific period, typically 19 years. This measurement is significant in maritime navigation and coastal management because it helps establish a consistent reference point for understanding tidal variations in a given area. By focusing on the higher high tide, MHHW takes into account the natural variations and influences that can affect tide heights, such as geographical features and atmospheric conditions.

In contrast, the other options do not correctly define MHHW. Average height of all tides would include both highs and lows, which would dilute the information needed for specific navigational purposes. The average height of the lower of the two daily low tides would not provide an accurate representation of higher water levels, which is crucial for safe navigation and infrastructure planning. Lastly, using the average height during slack water is not applicable, as slack water refers to the moment when the tide is not rising or falling, rather than a measurement of tidal heights. Thus, MHHW specifically provides a reliable estimate for higher tide conditions, which is essential for various nautical operations.