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Tidal range is the difference in height between high tide and low tide. Tides are the rise and fall of sea levels caused by gravitational forces exerted by the Moon and Sun , by Earth's rotation and by centrifugal force caused by Earth's progression around the Earth-Moon barycenter .
Some height values on charts, such as vertical clearances under bridges or overhead wires, may be referenced to a different vertical datum, such as mean high water springs or highest astronomical tide (HAT) (for "HAT" see tidal range). Tide tables give the height of the tide above a chart datum making it feasible to calculate the depth of water ...
Mean high water springs (MHWS) – The average of the two high tides on the days of spring tides. Mean high water neaps (MHWN) – The average of the two high tides on the days of neap tides. Mean sea level (MSL) – This is the average sea level. The MSL is constant for any location over a long period.
Tide heights at intermediate times (between high and low water) can be approximated by using the rule of twelfths or more accurately calculated by using a published tidal curve for the location. Tide levels are typically given relative to a low-water vertical datum, e.g. the mean lower low water (MLLW) datum in the US. [2]
The tidal range in the Bay of Fundy is about 16 metres (52 ft); the average tidal range worldwide is only one metre (3.3 ft). Some tides are higher than others, depending on the position of the moon, the sun, and atmospheric conditions.
In many parts of the world the tides approximate to a semi-diurnal sine curve, that is there are two high- and two low- tides per day. As an estimate then each period equates to 1 hour, with the tide rising by 1, 2, 3, 3, 2, finally 1 twelfths of its total range in each hour, from low tide to high tide in about 6 hours, then the tide is ...
That could mean high tides are as much as half a foot higher in the next few years, he said. For the highest tides of the year, King Tides, that could make a big difference in low-lying places ...
A tidal prism is the volume of water in an estuary or inlet between mean high tide and mean low tide, [1] or the volume of water leaving an estuary at ebb tide. [2]The inter-tidal prism volume can be expressed by the relationship: P=H A, where H is the average tidal range and A is the average surface area of the basin. [3]