Page 21 - 2021PSF-ResilientCoastsForSalmon-NewLogo-Primer-Web

Photo by: Mitch Miller

TIDAL PREDICTIONS (7 DAYS)
4

3
HEIGHT (m) 2

1

0
9/10 9/11 9/12 9/13 9/14 9/15 9/16 9/17

DATE
Figure 4.2 – Example of a mixed semi-diurnal tide chart at Ladysmith for the week of September 10, 2021.
Each 24 hours period has two uneven high tides and two uneven low tides.
Source: Fisheries and Oceans Canada 2021

Tidal Cycle
When you visit the beach, the sea level appears to low tides are different from each other (Figure 4 .2) .
be changing — sometimes by the minute — this The area between the highest high tide and lowest
is a result of tides . Tides occur because of the low tide is called the intertidal zone . Here, there is a
gravitational pull from the sun and the moon, as well great diversity of life that has adapted to alternating
as the rotation of the earth . In British Columbia, our between the extremes of being submerged and
tidal pattern is called mixed semi-diurnal, meaning exposed . Many significant ecological processes occur
there are approximately two high tides and two low in the intertidal zone, such as forage fish spawning
tides each day and the height of the two high and and shorebird foraging .

BOTTOM LINE:

If left to play out naturally, the coastal physical and ecological processes

described above maintain dynamic and resilient shorelines that
can adapt to variable conditions. However, human made shoreline
armouring structures, including seawalls and rock riprap, interfere with

these processes. These are discussed further in the next section, Chapter 5.

20