CHAPTER 2
TIDES AND CURRENTS Tides and currents will have an important influence on just about every aspect of sailing—especially when you are planning a course to sail, avoiding obstructions and docking or landing at a mooring.
A tide table (partially shown, right) gives you daily information regarding the predicted times of high and low tides and the heights of the tides.
Tides are defined as the vertical movement of water caused by the gravitational pull of the Earth and the Moon. We describe tides as being high or low, and they occur daily and at regular intervals. On the U.S. East Coast and West Coast, there are typically two high and two low tides each day, but the difference in water height can vary depending on location. A tide that is going out or dropping is said to be ebbing, while an incoming tide is flooding. The period in between, with very little water movement, is known as slack. With a watch, a tide table and a chart, you can determine the depth of the water in which you are sailing at any time. Most freshwater lakes do not have tides.
Current is the horizontal flow of water and is described in terms of the direction and speed the water is moving. Current can be caused either by water flowing from a higher elevation to a lower elevation like a river, or by ocean tides going out (ebbing) and coming in (flooding).
These photos, taken at the same location, show the difference between high and low tide. Consulting a tide table and a chart will help you avoid running aground during a low tide.
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Current is affected by water depth. Deep water will increase the speed of current or tide; shallow water will reduce the velocity of current. It is important to know the direction and speed of current when you are sailing. Looking at certain indicators—such as a floating object, a fixed mooring, channel marker or docks—are good ways to determine current. Current flowing past these objects can create a swirl or “wake” that moves in the direction of the current, making the stationary object appear as if it were moving.
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