Importance of Tides

Tides are not just a spectacle of the ocean; they are a predictable, measurable force that human activity has learned to use. Because tides are caused by the known positions of the earth, moon, and sun, their timing and height can be calculated accurately well in advance. This predictability is the foundation of their practical value.

The most direct beneficiaries are navigators and fishermen. Knowing exactly when the tide will rise or fall lets them plan their departures, arrivals, and fishing trips around the movement of water rather than against it. Tidal flows are therefore of great importance in navigation, guiding ships safely through channels that might otherwise be too shallow.

Tidal height matters most at harbours located near rivers or within estuaries. These entrances often have shallow 'bars' — ridges of sand or silt — that can block ships and boats from entering. A high tide raises the water level enough to clear these bars, allowing vessels to pass safely. Without this lift, many harbours would be inaccessible for large parts of the day.

Tides also do essential environmental work. They help in desilting — carrying away the sediments that accumulate in river estuaries — and in removing polluted water from the same areas. Each tidal cycle flushes the estuary, keeping it cleaner and deeper than it would otherwise be. …