Tide is the vertical
motion of the water caused mainly by the gravitational effects of the sun and the moon. When there is no
vertical motion this is referred to as stand. Current, or more correctly, tidal stream is the horizontal flow
of the water. The current coming in from the sea is called a flood current while the current flowing out to
sea is the ebb current. When there is no horizontal movement this is referred to as slack, slack water or the
turn.
“Commonly used expressions like “flood tide” and “ebb tide” should be avoided, as
they confuse the horizontal motions of tidal currents with the vertical displacements of the tide” Oceanography of
the British Columbia Coast – Richard E Thomson Published by Department of Fisheries and
Oceans.
By using the Tide and Current Tables correctly you will be able to predict the depth at low
and high water and be able to use the current to your advantage.
One question many boaters ask is how are the Tables
arranged? One of the commercial books is arranged in alphabetical order while the Official Tables produced by
the Canadian Hydrographic Service are arranged in order from seaward. They start at the western entrance of
Juan de Fuca Strait, go down into Puget Sound and then northwards through the Strait of
Georgia.
AReferencePort is where the Tidal height has been measured
such as Fulford Harbour which is the Reference Port of the Southern Gulf Islands. There are tables of corrections
to theSecondary Ports. AReference Station gives the details of the currents and similarly there are tables of corrections to
theSecondary Stations.
It is critical to understand that the time of low
water stand and the time of the turn to flood do not normally occur at the same time. In the Sidney area, the
difference of the time of low water stand and the turn to flood in Sidney Channel can be 1 hour and 40
minutes or greater.Likewise
the time of high water stand and the turn to ebb do not correspond.
CHS has
announced they will not be printing the Tide and Current
Tables.
