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Figure 7.2 – Coastal squeeze occurs where structures like seawalls impede the natural shoreline to adjust to rising sea
levels. Natural shorelines leave room for vegetation and tidal zones to move landward.
Illustration by: Holly Sullivan

Saltwater Intrusion

As seawater moves landward over time and floods
low lying areas more often, a phenomenon called
saltwater intrusion can occur . Saltwater intrusion is
the movement of salty water into freshwater aquifers .
Because saline water has a higher mineral content
than freshwater, it is denser and has a higher water Salmon will experience a reduction in
pressure . As a result, saltwater can push inland
beneath the freshwater . This will impact the water food resources such as vital Pacific
quality of groundwater, making it unsuitable for sand lance, as a result of loss of critical
drinking or irrigation . Those in coastal areas that rely spawning habitats for forage fish.
on well water will need to secure alternative sources
of water if they become affected .

Coastal Squeeze
When shorelines are hard armoured with seawalls Reducing the amount of armoured shoreline
and riprap, it prevents habitats from naturally migrating and preventing future armouring is critical to
landward with sea level rise (Figure 7 .2) . As sea levels the ecological resilience of BC’s coasts . The fact
rise, the high-water line is restricted by these remains that sea levels are rising, and protecting
structures and coastal processes are impeded . This our communities is a priority . The good news is
reduces intertidal habitat and eventually can cause that there are sustainable approaches for coastal
a complete loss of intertidal areas and the associated protection that can protect our homes from climate
species . This is known as coastal squeeze . change related damage in the near term while
Forage fish, an important food source for salmon, minimizing our impacts on valuable shoreline
rely on intertidal habitat for spawning . Where coastal ecosystems!
armouring structures are in place, their critical For more information and interactive maps about
spawning areas will be squeezed out . The populations sea level rise in Southern Vancouver Island follow
of forage fish will suffer as will the entire food chain if this link: Surging Seas: Seeing Choices.
natural coastal processes and habitats are not intact .
To learn more about forage fish, see Chapter 2 .

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