Nat Hazards (2009) 48:59–72
DOI 10.1007/s11069-008-9248-0
ORIGINAL PAPER
Landslides impacting linear infrastructure
in west central British Columbia
M. Geertsema Æ J. W. Schwab Æ A. Blais-Stevens Æ M. E. Sakals
Received: 22 November 2007 / Accepted: 29 April 2008 / Published online: 22 May 2008
! Springer Science+Business Media B.V. 2008
Abstract Destructive landslides are common in west central British Columbia. Landslides include debris flows and slides, earth flows and flowslides, rock falls, slides, and
avalanches, and complex landslides involving both rock and soil. Pipelines, hydrotransmission lines, roads, and railways have all been impacted by these landslides, disrupting
service to communities. We provide examples of the destructive landslides, their impacts,
and the climatic conditions associated with the failures. We also consider future landsliding potential for west central British Columbia under climate change scenarios.
Keywords
Landslide ! Linear infrastructure ! Climate change ! British Columbia
1 Introduction
West central British Columbia (BC) is a rugged but sparsely populated portion of the
province (Fig. 1). Nevertheless, the area hosts important transportation corridors, linking
its communities and providing Canadian access to the orient. Infrastructure includes roads,
railways, hydrotransmission lines, and hydrocarbon pipelines. The cities of Kitimat and
Prince Rupert are important deep sea ports that are expected to undergo substantial growth
to meet the needs of growing Asian economies. Recently, major oil pipelines have been
proposed, connecting the North American network to a Pacific tidewater port at Kitimat.
The purpose of this article is to provide examples of various types of destructive
landslides that impact linear infrastructure in west central BC. The list is by no means
M. Geertsema (&)
Northern Interior Forest Region, BC Forest Service, 1011, 4th Avenue, Prince George,
BC, Canada V2L 3H9
e-mail: marten.geertsema@gov.bc.ca
J. W. Schwab ! M. E. Sakals
Northern Interior Forest Region, BC Forest Service, Smithers, BC, Canada V0J 2N0
A. Blais-Stevens
Geological Survey of Canada, 601 Booth Street, Ottawa, ON, Canada K1A 0E8
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Fig. 1 Landslides and linear infrastructure in west central BC. The landslides shown are described in the
text and represent a portion of actual landslides in the area. Numbers represent landslides that are listed in
Table 1
all-inclusive, and many more events have occurred that are not recorded here. We also
consider the impact of projected climate change on the incidence of future landslides.
2 Setting
The study area is located within the coast, Hazelton, and Skeena mountain ranges of
northwestern BC (Holland 1976; Mathews 1986). These mountains are part of the northwest trending geological zones within the Canadian Cordillera called the Coast-Cascades
Belt and the Intermontane Belt. The area consists of rugged mountains cut by deep valleys
containing glacial and post-glacial sediments. Most mountains have rounded, dome-like
tops from glacial overriding with relatively uniform elevations varying between 1,800 and
2,400 m. Higher peaks, up to 2,800 m, are more rugged as they were nunataks during the
last glaciation (Holland 1976; Clague 1984).
Topography strongly influences air temperature and precipitation in the area. Temperatures decrease with increasing elevation and distance inland. For example, in January,
the mean coastal temperature at Prince Rupert (52 masl) is 1.8"C. In comparison, roughly
350 km in-land in the Bulkley Valley at Smithers (515 masl), the mean temperature is 10.5"C. Moreover, mean July temperatures vary between 14 and 17"C in the valleys and
decrease by several degrees with elevation. The predominant flow of moisture-laden air
travels toward the east from the Pacific Ocean. Mean annual precipitation values for
coastal mountains exceed 2,500 mm and can be greater than 3,500 mm in some areas.
There is a marked decrease in precipitation toward the east. For example, in the Bulkley
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Valley, mean annual precipitation values range between 400 and 500 mm. The main
valleys of the study area lie within the Coastal Western Hemlock and Sub-Boreal Spruce
biogeoclimatic zones. At higher elevations, the Mountain-Hemlock, Engelmann SpruceSubalpine Fir, and Alpine Tundra zones occur (Meidinger and Pojar 1991).
On the coast, the bedrock lies within the Coast-Cascades Belt. It is mainly composed of
Paleozoic to early Tertiary granitic rocks and Proterozoic to Paleozoic high-grade metamorphic rocks. Toward the east, the bedrock is part of the Intermontane Belt, which
consists of sedimentary and volcanic rocks of Jurassic–Cretaceous age intruded by Cretaceous–early Tertiary felsitic to porphyritic plugs (Duffel and Souther 1964).
The surficial geology of the area was mapped and described by Clague (1984). During
the last glaciation the area was covered by the Cordilleran Ice Sheet. The types of sediments deposited were mainly cobbly to bouldery tills. During glaciation, the weight of the
ice sheet caused isostatic depression of the lithospheric crust. During deglaciation
(10–11 ka BP), the crust slowly rebounded, but at a much lower rate than the melting of the
ice sheet. This caused coastal river valleys to be inundated by marine waters. Glaciomarine
sediments, mainly laminated silts and clays, were deposited as glaciers melted and
retreated up the valleys. In areas where ice was at a standstill for an extended period of
time (e.g., Terrace), deltaic sands and gravels were deposited.
The northwest trending rugged topography poses serious challenges for linear development. Only certain valleys and passes are suitable for east–west oriented infrastructure.
Together with steep, unstable rock masses and weak soils, the terrain in west central BC
places constraints on development.
3 Methods
Landslide data in the study area have been compiled by the BC Forest Service research
program since the mid-1970s. Landslides were identified from earlier reports, aerial
photography, and satellite imagery. Their dimensions and travel angles were obtained from
field measurements and from orthorectified aerial imagery. Volumes were calculated from
field measurements and from detailed pre- and post-landslide digital elevation models.
Landslides were classified according to Cruden and Varnes (1996) and Hungr et al. (2001).
3.1 Landslide types impacting linear infrastructure
Numerous types of landslides are common in the varied terrain of west central BC. We
provide examples of a few of the landslides that have damaged linear infrastructure in the
region. We also make reference to a number of significant landslides that have not damaged infrastructure. Included are large rock slides, some of which transformed into debris
avalanches and/or flows, debris flows, debris slides and avalanches, earth flows in glacial
lake sediments, in colluvium and in till, and flowslides in sensitive glaciomarine sediments
and in glaciolacustrine deposits. We define slides as movements along one or several
discrete rupture surfaces and flows as movements with significant internal distortion and
many short-lived rupture surfaces (Cruden and Varnes 1996). Like Hungr et al. (2001), we
use the term avalanche for unconfined flows and flow for movements in channels. We use
earth flow in the traditional sense of a slow moving body of plastic earth with a lobate zone
of accumulation. We restrict the term flowslide to rapid translational movements in glaciomarine and glaciolacustrine clays. See Table 1 for landslide descriptions. The locations
of the described landslides and others are shown in Fig. 1.
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Table 1 Landslide data
Number
on map
Landslide name
Date
Latitude/longitude
Infrastructure
impacted
I. Landslides in rock
Rock slide
1
Fossil Bed
Prehistoric
54"300 N, 127"530 W
Forest road
2
Kitsequela
2006
55"050 N, 127"560 W
Highway
3
Cedarvale
2004
54"500 N, 128"200 W
Highway
4
Dungate
Prehistoric
54"200 N, 126"340 W
5
Buck Creek
Prehistoric
54"220 N, 126"360 W
Prehistoric
54"230 N, 126"220 W
Rock fall–avalanche
6
China Nose
Rock spread
7
Parrot 1
Ongoing
54"050 N, 126"180 W
8
Parrot 2
Prehistoric
54"040 N, 126"170 W
II. Landslides in rock and soil
Rock slide–debris avalanche
9
Sutherland
2005
54"220 N, 124"550 W
Rock slide–debris avalanche–debris flow
10
Harold Price
2002
55"040 N, 126"570 W
Rock slide–debris flow
11
Zymoetz
2002
54"240 N, 128"130 W
Road, pipeline
12
Howson I
1991
54"330 N, 127"440 W
Pipeline
13
Howson II
1999
54"310 N, 127"460 W
Pipeline
14
Chicago Creek
*4000 BP
55"110 N, 127"380 W
Indian village
15
Bishop Bay
2002
53"280 N, 128"510 W
III. Landslides in soil
Debris slides–avalanches–flows
16
Kaien Island
(2 events)
1908, 1957
54"170 N, 130"160 W
Road
17
Kaien Island
(3 events)
1957, 1974, 1985
54"180 N, 130"180 W
Road, power line
18
Kaien Island
([5 events)
1891, 1917,
1974, 1978
54"150 N, 130"200 W
Rail
19
Porcher Island
(2 events)
1998, 2002
54"000 N, 130"200 W
Power line
20
Port Simpson
(13 events)
2002
54"290 N, 130"210 W
Road and power line
21
Inverness
([5 events)
1891,1917, 1935,
1972, 1978
54"120 N, 130"140 W
Building, roads, rail
22
North Pacific
Cannery
(2 events)
2002
54"110 N, 130"130 W
Road
23
Inverness Cannery
([5 events)
1891, 1917, 1962,
1978, 2002
54"100 N, 130"100 W
Building, rail, roads
24
Twidledee
2005
54"130 N, 130"060 W
Highway
25
Work Channel
2005
54"160 N, 129"570 W
Pipeline
26
Green river
1917
54"120 N, 130"000 W
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Table 1 continued
Number
on map
Landslide name
Date
Latitude/longitude
Infrastructure
impacted
Debris flow
27
Hotspring
1978
54"100 N, 129"520 W
28
Legate I & II
2004
54"430 N, 128"150 W
Highway
29
Legate III
2007
54"430 N, 128"150 W
Highway
Earth flow
30
Bulbous toe
Ongoing
54"370 N, 127"210 W
Transmission line
31
Morice I
1984
54"150 N, 126"500 W
Public road
32
Morice II
1984
54"140 N, 126"500 W
Public road
33
Morice III
1984
54"130 N, 126"500 W
Public road
34
Kitsequecela
Ongoing
55"040 N, 127"500 W
Highway
Ongoing
54"380 N, 127"250 W
35
Telkwa River
Flowslide–glaciolacustrine
36
Houston Tommy
(3 events)
Prehistoric, 1950
54"160 N, 126"580 W
37
Cheslaslie
Ongoing
53"270 N, 125"430 W
Forest road
Flowslide–glaciomarine
38
Khyex
2003
54"170 N, 129"480 W
Pipeline
39
Mink
1994
54"260 N, 128"400 W
Rail
40
Lakelse N
1962
54"230 N, 128"320 W
Highway
41
Lakesle S
1962
54"240 N, 128"310 W
Highway
Historic
54"080 N, 125"500 W
Washout-flow
42
Tchesinkut Creek
Non-landslide alluvial fans
43
Hunter Creek
1991
54"130 N, 128"120 W
Forest road, bridge
44
Gosnell
1990s
54"070 N, 127"390 W
Forest road, bridge
45
Gosnell-Burnie
54"100 N, 127"450 W
Fig. 2 Plot of landslide runout
(height over length (H/L)) versus
volume for select landslides in
west central BC. Note the low
H/L ratios for glaciomarine
landslides
Travel angles of landslides discussed below are plotted in Fig. 2. The travel angle, a
measure of the vertical difference of the lowest and highest points on a landslide (H) as a
ratio of the length of the travel path (L), is a useful metric to aid in landslide risk zonation.
In the study area the lowest travel angles range from 1.4" for glaciomarine flowslides up to
a minimum of 9.9" for rock slides that entrain soil.
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The landslides damage infrastructure in two main ways. (1) Most commonly infrastructure is in the landslide runout zone and is struck by moving debris. (2) Occasionally,
infrastructure is placed on unstable ground and is moved suddenly or episodically as the
main body of the landslide moves. Where rock slides, debris flows, and debris slides
described here resulted in damage to infrastructure, it was always the result of the first case,
where objects were struck by moving material. In contrast, earth flows and flowslides
damaged infrastructure located in the zone of depletion by carrying it along during
movement. See Cruden and Varnes (1996) for landslide terminology.
Landslides also can have varying causes and triggers. Examples of causes can be
inherent weakness in material, valley deepening, glacial debuttressing, road construction,
and excavation. Triggers can be rainfall, snowmelt, site loading, and seismic activity.
Shallow landslides such as debris slides and flows are often triggered by intense rainfall.
Deep-seated landslides such as large rock slides, earth flows, and flowslides tend to have
longer hydrological response times (Egginton 2005).
3.1.1 Complex rock slides and avalanches
Six large rock slides have occurred in west central BC since 1978, five of which occurred
since 1999, and four since 2002 (Fig. 1; Table 1). Three of the six rock slides severed
natural gas pipelines. All of the rock slides had relatively long runouts with travel distances
up to 4.3 km and travel angles as low as 9.9" (Geertsema and Cruden 2008).
The 1999 Howson rock slide (Fig. 3a) occurred at 03:00 h PDT on 11 September. The
rock slide traveled 2.7 km, entraining till and colluvium. It ruptured a natural gas pipeline
and formed a lake. The initial rockslide involved 0.9 Mm3 and the entrained volume is
estimated to be 1.5 Mm3 (Schwab et al. 2003). It had a travel angle of 25.6" (Geertsema
and Cruden 2008). The initial movement involved toppling and cliff collapse onto a
glacier. The debris traveled over the glacier and dropped into a steep sided valley, where it
entrained soil and transformed into a debris flow.
On 8 June 2002, a rock slide involving 1.6 Mm3 transformed into a debris flow,
damming the Zymoetz River, and severing a natural gas pipeline (Fig. 3b; Schwab et al.
2003; Boultbee et al. 2006). The landslide traveled 4.3 km with an average travel angle of
16.3" (Geertsema and Cruden 2008). McDougal et al. (2006) demonstrated the importance
of entrainment of fine-grained sediment along the debris flow portion of the landslide. An
estimated 0.5 Mm3 of debris, including blocks up to 7 m in diameter, dammed the river,
causing flooding 1.5 km upstream. Although the dam was overtopped almost immediately,
it is still an obstruction to river flow. Access to a 3,000-km2 watershed was blocked for
more than 1 year due to the flooding of a major forest road.
The remaining rock avalanches did not damage infrastructure but occurred near areas of
potential development. Two of these large rock slides also occurred in 2002 (Geertsema
et al. 2006a). The Harold Price and Bishop Bay landslides occurred near Smithers and
southeast of Prince Rupert on the outer coast, respectively (Fig. 1). The Harold Price
landslide (Fig. 3c) initiated in what appeared to be a rock glacier in a cirque basin sometime
between 22 and 24 June 2002. Interstitial ice was found in the main scarp. After travelling
1.3 km the rock slide transformed into a debris avalanche entraining till and colluvium. The
debris avalanche channelized into a debris flow of 2.2 km from its source. The total travel
distance of the landslide was 4 km with a travel angle of 9.9" (Geertsema and Cruden 2008).
The volume was estimated to be 1.6 Mm3. The Bishop Bay landslide (Fig. 3d) is less
precisely dated (Geertsema et al. 2006a). It probably initiated as a rockfall. The landslide
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Fig. 3 Large, long runout rock slides in west central BC. See Fig. 1 for locations. (a) The 1999 Howson
rock slide entrained till and colluvium, severing a natural gas pipeline (1). Note the hydrotransmission line
(2) and the landslide dammed lake (3). (b) The 2002 Zymoetz rock slide transformed into a channelized
debris flow, dammed the Zymoetz River, flooded an important Forest Service Road for more than a year, and
ruptured a pipeline. The landslide traveled 4 km. (c) The 2002 Harold Price rock slide transformed into a
debris avalanche and then into a channelized debris flow, traveling more than 4 km. (d) The 2002 Bishop
Bay rock slide on the outer coast traveled 1.1 km. (e) The 2005 Sutherland rock slide transformed into a
debris avalanche and traveled 1.6 km
traveled 1.1 km over a vertical range of 370 m and entrained sandy, bouldery till derived
from granodiorite. It had a travel angle of 18" (Geertsema and Cruden 2008).
On 13 July 2005, a complex rock slide–debris avalanche occurred near Sutherland River
(Blais-Stevens et al. 2007), 40 km west of Fort St. James, British Columbia (Fig. 3e). The
landslide impact was powerful enough to leave a seismic signal at the Fort St. James
seismic station. The rapid landslide traveled 1.6 km at a travel angle of 11.3" (BlaisStevens et al. 2007) and involved 3 Mm3 of volcanic rock and soil. The landslide
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bifurcated in the runout zone. Pre-slide deformation was evident on aerial photographs, and
the slide site had been heavily impacted by mountain pine beetle.
3.1.2 Debris flows and floods
Debris flows and floods are common destructive landslides in west central BC. They typically initiate in steep source areas, travel through gullies, and deposit on fans in the valley
bottoms. Debris flows intergrade to debris floods (hyperconcentrated flows) and floods, with
decreasing sediment concentrations. Many fans in west central BC are the product of all
three processes (Wilford et al. 2003). All three processes can destroy infrastructure.
An example of a fan that is traversed by a major highway and subject to episodic debris
flows (Fig. 4) is near Legate Creek (Fig. 1; Table 1). Two debris flows closed the highway
at separate times in July and August 2004 with volumes of 7,000 and 20,000 m3,
respectively. On 28 May 2007, a much larger debris flow (2.7 km long and *250,000 m3)
crossed the highway, killing two people. Scars on trees record the 1978 event as well as an
earlier event in the 1920s.
Large fans at Hunter Creek (east of Kitimat), Gosnell Creek (West Houston), and
Sinclair creek (west of Smithers) (Fig. 1; Table 1) routinely wash out roads during flood
periods and cause considerable road maintenance issues. Debris and water floods are more
common on these large fans than debris flows, but linear infrastructure placed on these
landforms still requires careful hydro-geomorphological assessment.
Fig. 4 A debris flow at Legate
Creek (east of Terrace) crossed
the highway twice in 2004 and
once in 2007. The 2007 event
pictured here resulted in two
fatalities. Photo courtesy: Ralph
Ottens, BC Forest Service
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3.1.3 Debris slides and avalanches
Shallow, rapid debris slides, and avalanches occur throughout west central BC but are
particularly common on the coast in shallow soils draping steep bedrock (Figs. 1 and 5;
Table 1). These landslides typically initiate during intense rainstorms, after certain antecedent conditions met including soil moisture, total storm rainfall, rainfall intensity, and
snowmelt input (Jakob et al. 2006). Debris slides and avalanches close roads and rail lines
on an almost annual basis and occasionally sever natural gas pipe lines and hydrotransmission lines (Septer and Schwab 1995).
Because the west side of the Coast Range is much wetter than the east side, more
shallow landslides occur near Prince Rupert than east of the mountains. In October 2002,
an intense storm triggered more than 12 debris avalanches that took out the power to a
small community north of Prince Rupert and also disrupted road and rail service. Similar
landslides removed power poles serving a small community on Porcher Island south of
Prince Rupert in 1998 and in 2001. Landslides often occur in clusters and are triggered by
storms. Major historical storms that triggered debris avalanches and flows, impacting rail
and more recently road transportation, occurred in the Prince Rupert area in the years of
1917 1957, 1978, and 1988 (Schwab 2002) and in 2002 and 2005.
3.1.4 Earth flows
Earth flows occur in a variety of materials ranging from till and lake sediment to colluvium
(Fig. 1; Table 1). Rapid, low gradient earth flows can intergrade to the clay flowslides of
Hungr et al. (2001) and tend to occur only in advance phase lake sediments, buried by till
Fig. 5 Storm-triggered shallow
debris avalanches initiated during
a 2002 rainstorm in a clearcut
above the North Pacific Cannery
near Prince Rupert
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Fig. 6 An advancing lobe of the ‘‘Bulbous Toe’’, an earth flow west of Smithers involves fine textured
colluvium and is traversed by a hydrotransmission line (1). One of the towers requires periodic adjustment
(Geertsema et al. 2006a). The slower moving earth flows in west central BC can occur in
all these materials.
Slow moving earth flows reactivated along the Morice River road following road
upgrades in the 1970s and a major wild fire in 1983. These landslides covered areas from
10 ha to over 100 ha in size. Millions of dollars were spent stabilizing the slopes and
repairing a 15-km section of the road. The failures occurred in till and glaciolacustrine
sediment covered with till.
A large landslide, referred to informally as the Bulbous Toe, in the Telkwa River valley
(Fig. 6) underwent rapid movement in prehistoric time (BC Forest Service, unpublished
data). In the historic period a portion of the landslide continues to advance as a slowmoving earth flow of 2.3 km in length. A major transmission line traverses the landslide,
and adjustments are periodically required for one of the towers. About 30 cm/year of
movement over the past 10 years has occurred along the tower. The prehistoric landslide
involved more than 150 Mm3 of material including colluvium derived from tuffaceous
volcaniclastic rock. Other locations within the Telkwa valley and within the volcanic rocks
of the Telkwa formation are also experiencing landslide movement and sagging slopes
(Kitnayakwa River, Schwab and Kirk 2003).
3.1.5 Flowslides
Large flowslides involving sensitive glaciomarine sediments have destroyed a railway, a
highway, and a pipeline in the western portion of the study area (Fig. 1; Table 1). They
tend to move along nearly horizontal gradients, on slopes of up to 3".
Septer and Schwab (1995) gave a brief account of a flowslide south of Terrace that
occurred during rail bridge construction across Alwyn Creek. The landslide occurred at
Mile 6.6 on the Canadian National railway line between Terrace and Kitimat and was
reported in the Terrace Standard on 24 June 1953. The landslide buried bulldozers and
other construction equipment and resulted in the construction of an s-shaped trestle.
Landslide dimensions were not measured.
Two separate flowslides at Lakelse Lake ruptured the highway between Terrace and
Kitimat in May and June 1962 (Clague 1978; Geertsema and Schwab 1997). Both landslides debouched into Lakelse Lake, carrying vehicles and equipment with them. Loading
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Fig. 7 The 2003 Khyex landslide ruptured a natural gas pipeline (arrows), disrupting service to Prince
Rupert for 10 days. The landslide occurred primarily in glaciomarine sediments
from a spoil berm associated with highway construction was the likely trigger in both
cases. The landslides were not retrogressive, since they were triggered, where the highway
crossed them, near the mid points of the zones of depletion. They involved about 11 and
15 Mm3, respectively, and traveled extremely rapidly (Ministry of Transportation,
unpublished data) up to 3 km at gradients of at most 1.4" (Geertsema and Cruden 2008).
A large flowslide occurred around January 1994 at Mink Creek (Table 1) and was
classified by Geertsema et al. (2006b) as a retrogressive earth flow–earth spread. The
landslide, involving 2.5 Mm3 of glaciomarine sediment, traveled 1.6 km at 1.7" (Geertsema and Cruden 2008). The landslide dammed Mink Creek, creating a lake over 1.2 km
long extending to beyond a railway tressle (Geertsema and Torrance 2005).
In November 2003, a large flowslide on Khyex River ruptured a natural gas pipeline
(Fig. 7), disrupting service to Prince Rupert for approximately 10 days (Schwab et al.
2004a, b). The landslide involved 4.7 Mm3 of material and was 1.85 km long from crown
to tip with a travel angle of 2.6" (Geertsema and Cruden 2008). The river was dammed
over a distance of 1.7 km, and water was backed up for 10 km.
A series of large, rapid, low gradient flowslides near Houston involve areas of up to
100 ha. A 40-ha flow along Houston Tommy Creek that occurred in the 1950s involved
more than 15 Mm3 of material (Fig. 1; Table 1). The landslides were up to 1.2 km long
with travel angles as low as of 6.5" (Geertsema and Cruden 2008). These landslides have
not impacted linear infrastructure but occur adjacent to developed areas.
3.1.6 Bedrock spreads
The Nechako plateau situated south and east of Houston is an area of flat and gently
dipping Tertiary lava flows that cover older volcanic and sedimentary rocks and intrusive
rocks of upper Jurassic and Cretaceous age. Much of the bedrock is obscured by deep
glacial drift. Spreading is occurring along 2.5 and 1.3 km west facing scarps in the Parrot
Creek valley involving possibly up to 150 and 50 Mm3 of material, respectively (Fig. 1;
Table 1).
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4 Future hazard regimes
Landslides in mountainous terrain are strongly influenced by climatic factors, including
precipitation and temperature (Evans and Clague 1994). Catastrophic landslides at high
elevations may be especially responsive to increases in temperature. Researchers have
suggested that recent melting of glaciers in BC has debuttressed rock slopes adjacent to
glaciers, causing deep-seated slope deformation and catastrophic failure (Holm et al.
2004), and Howson Range (Schwab et al. 2003; Fig. 3a).
Alpine permafrost may be degrading under the present warmer climate, decreasing the
stability of slopes (Harris et al. 2001). Recent large rock avalanches in the European Alps
have been attributed to the melting of mountain permafrost, and this phenomenon may also
play a role in initiating landslides in northern BC, as in the case of the Harold Price
landslide (Fig. 3c).
The Mink Creek flowslide near Terrace occurred after nearly a decade of increasing
temperature and precipitation. Geertsema and Schwab (1997) provided evidence for an
increase in flowsliding 2,000–3,000 years ago in the Terrace area under wetter climatic
conditions. Almost all global circulation models predict warmer and wetter conditions in the
future for the Terrace area (Fig. 8); thus more such landslides may be expected in this area.
Large scale climate changes also have implications for forest insects and pathogens.
More than 80% of the mature lodgepole pine in BC is expected to succumb to the mountain
pine beetle within the next decade (Eng et al. 2005). These changes to the forest are
expected to have widespread hydrological impacts to the landscape and may predispose
slopes to accelerated landsliding.
Fig. 8 Annual climate change scenarios for 2020, 2050, and 2080 for Terrace, BC, with respect to a 1961–
1990 global climate model baseline. The points represent the results of 58 different global circulation
models, generally predicting a progressively warmer and wetter climate for Terrace. The data were obtained
from the Canadian Institute for Climate Studies web site (http://www.cics.uvic.ca) and is modified from
Geertsema et al. (2006b)
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5 Conclusions
Linear infrastructure is at continued risk from a variety of landslide types in west central
BC. The landslides range from shallow debris slides and flows to massive rapid, rock
slides, and slow moving earth flows and rapid flowslides. The risk is likely to rise under
scenarios of a warmer and wetter climate as the pressure for more infrastructure increases.
More research is required to assess future hazards. Remote sensing techniques could be
employed to assess slope deformation that often precedes catastrophic failure. Detailed
slope deformation and runout models should continue to be developed to predict slope
behavior and to better delineate hazard and risk zones in valleys and corridors.
Acknowledgments Dr. Theo van Asch and Dr. Brent Ward provided helpful reviews that improved our
manuscript. Earlier comments from Frank Maximchuck, Gord Hunter, and Jonathan Fannin are also much
appreciated.
References
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