The Theme
Climate warming is expected to cause warming of the oceans and
the partial melting of glaciers and ice-caps, resulting in a global
rise in sea level. By the end of this century, the global mean sea-level
rise could amount to 0.09 to 0.88 metres (Intergovernmental Panel on Climate Change 2001). In Canada,
where the total coastline exceeds 203 000 kilometres, sea level
rise is a significant issue.
This map shows the sensitivity of the coastlines of Canada to the
expected rise in sea level, due to climate warming. Sensitivity
here means the degree to which a coastline may experience physical
changes such as flooding, erosion, beach migration, and coastal
dune destabilization. It is measured by a sensitivity index, which
is a modified version of the coastal vulnerability index of Gornitz
(1990). This sensitivity index is obtained by manipulating scores
of 1 to 5 attributed to each of seven variables: relief, geology,
coastal landform, sea-level tendency, shoreline displacement, tidal
range, and wave height.
Sensitivity Projection
As shown in the map, sensitivity index scores range from 0.8 to
56.7. Two major regions of high sensitivity are identified: 1) Atlantic
Canada (much of the coasts of Nova Scotia, Prince Edward Island,
and New Brunswick); and 2) parts of the Beaufort Sea coast. Small
areas of high sensitivity occur in Quebec, Newfoundland and Labrador,
and British Columbia.
As sea level rises, storm surges will inflict greater damage on
communities located close to the level of the ocean. A reminder
of this was the flooding of Charlottetown, Prince Edward Island
by a storm surge in January 2000. Other communities at risk include
Placentia in Newfoundland and Labrador, and even downtown Halifax.
The lowlands at the head of the Bay of Fundy are also at risk from
storm surges. This area was devastated in the great storm surge
of 1869, the so-called 'Saxby Tide'. With accelerated sea-level
rise, the dykes will be breached by some of the high tides by the
middle of the century.
The other large area of high sensitivity is the Beaufort Sea, where some of the most rapid coastal erosion rates in Canada are found. The problem is exacerbated by
the thawing of permafrost in beach sediments. Storm surges commonly cause flooding in this region. Settlements such as Tuktoyaktuk will undoubtedly experience
further difficulties in the coming years. An additional concern in this region is that the extent and duration of sea ice will be reduced as the climate warms, thus
allowing storms to flood and erode the coast more frequently. Note that coastal erosion is restricted to summer months, and cannot occur in winter when the ocean is
frozen.
A rising sea level will result in more coastal erosion in this century. However, when compared with Europe and Japan, where expenditures on coastal protection are in
the many billions of dollars, Canada is fortunate in having low population densities and small amounts of infrastructure at risk. Awareness of the expected sea-level
rise and coastal erosion, which have been occurring for many thousands of years, should ensure that future developments are set back from threatened areas.
Photos of Canadian Coasts
Photographs A to L illustrate the diversity of Canadian coasts
and the wide range of impacts that might be expected.
Photograph A: Prince Patrick Island, Northwest Territories. This
low, ice-congested, sandy coastline is moderately sensitive to sea-level
rise (score 9.6), particularly to inundation and coastal retreat.
If the extent and duration of open water increases (due to global
warming), additional effects could include overwashing and development
of barrier beaches. Photo by R.B. Taylor. GSC 1998-038-A
[D] Click for larger version, 31 KB Photograph A. Prince Patrick Island, Northwest Territories
Photograph B: Bylot Island, Nunavut. This part of Bylot Island has a
low sensitivity overall (score 3.6). However, unlike the high, rocky
coast in the background, the low barrier beach could migrate landward
due to more frequent overwashing, particularly if the duration and
extent of ice cover decreased. The backbarrier lowland (right) is
vulnerable to inundation. Photo by R.B. Taylor. GSC 1998-038-B
[D] Click for larger version, 27 KB Photograph B. Bylot Island, Nunavut
Photograph C: Devon Island, Nunavut. A small percentage of eastern Arctic
coasts consist of tidewater glaciers. These are sensitive not only
to sea-level rise, but also to increases in open water extent and
duration which could increase calving rates and change coastal configuration.
This region has a moderate sensitivity (score 8.0). Photo by R.B. Taylor. GSC 1998-038-C
[D] Click for larger version, 27 KB Photograph C. Devon Island, Nunavut
Photograph D: Placentia, Newfoundland and Labrador. This is an example of a high sensitivity
location within a region assessed to be at low risk overall (score
3.2). The low, gravel beach-ridge plain has been inundated several
times in recent years during storms. This could occur more frequently
in the future. Photo by D.L. Forbes. GSC 1998-038-D
[D] Click for larger version, 41 KB Photograph D. Placentia, Newfoundland and Labrador
Photograph E: Îles-de-la-Madeleine, Quebec. At least three
nearshore bars dissipate wave energy on this dune coast (score 33.8).
Similar coasts exist throughout the southern Gulf of St. Lawrence.
Impacts could include dune instability, changes in configuration
of nearshore bars, and erosion of beaches. Photo by E.H. Owens. GSC 1998-038-E
[D] Click for larger version, 41 KB Photograph E. Îles-de-la-Madeleine, Quebec
Photograph F: Story Head, Nova Scotia. This region is highly sensitive
(42.8). The low, curving barrier beach in the photo retreats 8 metres
annually, and will soon become detached from the eroding drumlin
remnant in the foreground, exposing a sheltered inlet to Atlantic
storm waves. Accelerated sea-level rise will result in more frequent
changes at the outer coast, accompanied by the formation of new
barriers, and inundation of coastal marshes. Photo by J. Shaw. GSC 1998-038-F
[D] Click for larger version, 26 KB Photograph F. Story Head, Nova Scotia
Photograph G: Pointe aux Outardes, Quebec. Holocene deltas along
Quebec's North Shore are pockets of moderate sensitivity in an otherwise
low sensitivity region. Future sea-level rise would result in increased
coastal erosion and coastal mobility in these areas. Photo courtesy of J.-C. Dionne.
[D] Click for larger version, 49 KB Photograph G. Pointe aux Outardes, Quebec
Photograph H: North Richibucto Beach, New Brunswick. The gulf coast of New Brunswick
has moderate to high sensitivity levels - this area has a score
of 16.0. This low, sandy barrier beach could experience increased
rates of overwashing, retreat, and inlet migration. Erosion of peat
cliffs and inundation of backbarrier marshes could also be expected.
Photo courtesy of E.A. Bryant.
[D] Click for larger version, 37 KB Photograph H. North Richibucto Beach, New Brunswick
Photograph I: Northeast Graham Island, British Columbia. This is
one of two regions of high sensitivity in British Columbia - the
score is 24.8. The sandy bluffs in this photo are retreating up
to 12 metres annually, supplying sediment to prograding beaches
elsewhere in the region. Photo by C.L. Amos. GSC 1998-038-G
[D] Click for larger version, 46 KB Photograph I. Northeast Graham Island, British Columbia
Photograph J: Beaufort Sea coast, Yukon Territory. These 5 metre-high
bluffs at Kay Point are retreating due to thawing of ice wedges,
undercutting of polygons, and block slumping. The sensitivity score
of this region is 11.7. If open water duration increased, the coast
would be exposed to waves much higher than those that exist today.
Photo by D.L. Forbes. GSC 1998-038-H
[D] Click for larger version, 39 KB Photograph J. Beaufort Sea Coast, Yukon Territory
Photograph K: Toba Inlet, British Columbia. Like much of British
Columbia's coast, this fiord, surrounded by mountains rising above
1800 metres, is at low risk of modification by a sea-level rise.
The sensitivity index here is 1.9. Nevertheless, there could be
impacts, including inundation of the numerous bayhead deltas in
the region. Photo courtesy of J.P.M. Syvitski.
[D] Click for larger version, 27 KB Photograph K. Toba Inlet, British Columbia
Photograph L: West coast of Hudson Bay, Manitoba. This low coast
with sandy beaches, raised beaches, and coastal marshes is moderately
sensitive. The effects of global sea-level rise would be mitigated
by ongoing crustal rise here and elsewhere in Hudson Bay. Photo courtesy of I.P. Martini.
[D] Click for larger version, 32 KB Photograph L. West Coast of Hudson Bay, Manitoba
Data Source
J. Shaw, R.B. Taylor, D.L. Forbes, M.-H. Ruz, and S. Solomon. 1998.
Sensitivity of the Coasts of Canada to Sea-level Rise. Geological
Survey of Canada Bulletin 505. Ottawa.
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