SCIENCE REVIEW 1987 - Bedford Institute of Oceanography

which covered the landscape. The liner
material, silt and clay, was carried offshore
into deep basins or moved into estuaries by
tidal action. Sands and gravels were
incorporated into beaches and as the sea
level rose, beaches retreated landwards,
often over-riding the muddy sediments
deposited in estuaries and lagoons. Evidence
of the sea-level rise can also be found
offshore. Scientists working a short distance
off the coast in late 1987 used
geophysical methods to pinpoint the
location of bodies of former estuarine
deposits. Specific targets were identified for
coring operations to obtain samples for
studies of sea-level change and other
aspects of seabed geology. One of the cores
recovered on this cruise contained freshwater
peat, 8800 years old, at a depth of
20 m below present sea-level. Estuarine
sediment at a depth of 45 m was dated at
just under 11,000 years before present, and
contained pollen which showed a shrubtundra
environment.
It is expected that the additional global
sea-level rise will accelerate rates of change
at the coastline in this region. Coastal bluffs
which now have average retreat rates of
1 m per year (Taylor et al, 1985) may
erode faster. To keep pace with the
anticipated rise, many beaches may expe-
Fig. 1 This beach at Storey Head, on Nova Scotia’s Atlantic coast, is being monitored by coastal
geologists based at the Atlantic Geoscience Centre. It has been moving landwards at an average rate
of about 8 metres per year. Here the rise of sea level due to global change would add to the existing
regional subsidence of 30 cm per century. Beaches such as this may be destroyed From Forbes et al
(in review).
rience rapid landward migration or may
even be destroyed. Figure 1 shows the
dramatic changes at Story Head, one of a
number of beaches monitored by coastal
geologists based at the Bedford Institute of
Fig, 2 The settlement of Neil’s Harbour on Cape Breton Island after a storm surge in October 1983.
Total damage in the region was estimated to cost $2.7 million The projected sea-level rise would
increase the incidence of such events. Photo courtesy of R. B. Taylor.
Oceanography. It is possible that the rise
may exceed the rate of vertical accretion of
the salt marshes which fringe the numerous
estuaries in the region, eliminating this
important habitat.
Direct human impact
What about the direct impact on human
populations? Along the predominantly
rural Nova Scotia coastline, property loss
will continue and buildings will be threatened,
but these have long been accepted
hazards (Figure 2). Throughout the Maritimes
there are examples of settlements
which may be placed under increased risk.
For example, in southern Newfoundland
the town of Placentia (Figure 3), built on a
gravel beach-ridge plain (Shaw and
Forbes, 1987), is already susceptible to
flooding associated with extreme tides,
storm surges and high rainfall. A future sealevel
rise would increase the likelihood of
flooding (coastal protection structures are
now under consideration for the town).
The impact on human structures will be
greatest in large coastal urban areas. Some
studies have already been completed on the
possible effects in such locations. For
example, it has been concluded that a one
metre sea-level rise at Saint John, New
Brunswick, would cause an increase in the
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