In navigation, the effect of the tidal current is often of more importance
than the changing depth due to the tide; in fact, many mariners speak of
"the tide" when they actually have the flow of the tidal current in mind.
Currents can be defined as the horizontal movement of water, and may
be classified as either tidal or nontidal.
Tidal Currents. These currents are caused by gravitational interactions
between the Sun, Moon, and Earth just like the vertical rise and fall
called tide, which we have discussed. Study the terms associated with
When the horizontal movement of water is
toward shore or up a tidal river or estuary, the
current is said to be flooding.
When the horizontal movement of water is away
from shore or down a tidal river or estuary, the
current is said to be ebbing.
The period of time where there is little or no
current is called the minimum before flood or
Duration of The interval of time in which a tidal current is
Duration of The interval in which the current is ebbing. In a
normal semidiurnal tidal current, the duration of
flood and duration of ebb will each be
approximately 6 hours, but can vary.
The direction of the current is called SET, and is
expressed in the direction TOWARD which the
The velocity of the current is called speed of
current and is sometimes referred to as drift.