ORIGINAL PAPER

Landslides impacting linear infrastructurein 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. Land-slides include debris flows and slides, earth flows and flowslides, rock falls, slides, andavalanches, and complex landslides involving both rock and soil. Pipelines, hydrotrans-mission lines, roads, and railways have all been impacted by these landslides, disruptingservice to communities. We provide examples of the destructive landslides, their impacts,and the climatic conditions associated with the failures. We also consider future land-sliding 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 theprovince (Fig. 1). Nevertheless, the area hosts important transportation corridors, linkingits communities and providing Canadian access to the orient. Infrastructure includes roads,railways, hydrotransmission lines, and hydrocarbon pipelines. The cities of Kitimat andPrince Rupert are important deep sea ports that are expected to undergo substantial growthto meet the needs of growing Asian economies. Recently, major oil pipelines have beenproposed, 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 destructivelandslides 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 3H9e-mail: marten.geertsema@gov.bc.ca

J. W. Schwab ! M. E. SakalsNorthern Interior Forest Region, BC Forest Service, Smithers, BC, Canada V0J 2N0

A. Blais-StevensGeological Survey of Canada, 601 Booth Street, Ottawa, ON, Canada K1A 0E8

123

Nat Hazards (2009) 48:59–72DOI 10.1007/s11069-008-9248-0

all-inclusive, and many more events have occurred that are not recorded here. We alsoconsider 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 ofnorthwestern BC (Holland 1976; Mathews 1986). These mountains are part of the north-west trending geological zones within the Canadian Cordillera called the Coast-CascadesBelt and the Intermontane Belt. The area consists of rugged mountains cut by deep valleyscontaining glacial and post-glacial sediments. Most mountains have rounded, dome-liketops from glacial overriding with relatively uniform elevations varying between 1,800 and2,400 m. Higher peaks, up to 2,800 m, are more rugged as they were nunataks during thelast glaciation (Holland 1976; Clague 1984).

Topography strongly influences air temperature and precipitation in the area. Tem-peratures 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, roughly350 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 anddecrease by several degrees with elevation. The predominant flow of moisture-laden airtravels toward the east from the Pacific Ocean. Mean annual precipitation values forcoastal 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

Fig. 1 Landslides and linear infrastructure in west central BC. The landslides shown are described in thetext and represent a portion of actual landslides in the area. Numbers represent landslides that are listed inTable 1

60 Nat Hazards (2009) 48:59–72

123

Valley, mean annual precipitation values range between 400 and 500 mm. The mainvalleys of the study area lie within the Coastal Western Hemlock and Sub-Boreal Sprucebiogeoclimatic zones. At higher elevations, the Mountain-Hemlock, Engelmann Spruce-Subalpine 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 ofPaleozoic to early Tertiary granitic rocks and Proterozoic to Paleozoic high-grade meta-morphic rocks. Toward the east, the bedrock is part of the Intermontane Belt, whichconsists of sedimentary and volcanic rocks of Jurassic–Cretaceous age intruded by Cre-taceous–early Tertiary felsitic to porphyritic plugs (Duffel and Souther 1964).

The surficial geology of the area was mapped and described by Clague (1984). Duringthe last glaciation the area was covered by the Cordilleran Ice Sheet. The types of sedi-ments deposited were mainly cobbly to bouldery tills. During glaciation, the weight of theice 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 theice sheet. This caused coastal river valleys to be inundated by marine waters. Glaciomarinesediments, mainly laminated silts and clays, were deposited as glaciers melted andretreated up the valleys. In areas where ice was at a standstill for an extended period oftime (e.g., Terrace), deltaic sands and gravels were deposited.

The northwest trending rugged topography poses serious challenges for linear devel-opment. 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 BCplaces constraints on development.

3 Methods

Landslide data in the study area have been compiled by the BC Forest Service researchprogram since the mid-1970s. Landslides were identified from earlier reports, aerialphotography, and satellite imagery. Their dimensions and travel angles were obtained fromfield measurements and from orthorectified aerial imagery. Volumes were calculated fromfield 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. Weprovide examples of a few of the landslides that have damaged linear infrastructure in theregion. We also make reference to a number of significant landslides that have not dam-aged infrastructure. Included are large rock slides, some of which transformed into debrisavalanches and/or flows, debris flows, debris slides and avalanches, earth flows in glaciallake sediments, in colluvium and in till, and flowslides in sensitive glaciomarine sedimentsand in glaciolacustrine deposits. We define slides as movements along one or severaldiscrete rupture surfaces and flows as movements with significant internal distortion andmany short-lived rupture surfaces (Cruden and Varnes 1996). Like Hungr et al. (2001), weuse the term avalanche for unconfined flows and flow for movements in channels. We useearth flow in the traditional sense of a slow moving body of plastic earth with a lobate zoneof accumulation. We restrict the term flowslide to rapid translational movements in gla-ciomarine and glaciolacustrine clays. See Table 1 for landslide descriptions. The locationsof the described landslides and others are shown in Fig. 1.

Nat Hazards (2009) 48:59–72 61

123

Table 1 Landslide data

Numberon map

Landslide name Date Latitude/longitude Infrastructureimpacted

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 W5 Buck Creek Prehistoric 54"220 N, 126"360 W

Rock fall–avalanche

6 China Nose Prehistoric 54"230 N, 126"220 WRock spread

7 Parrot 1 Ongoing 54"050 N, 126"180 W8 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 WRock slide–debris avalanche–debris flow

10 Harold Price 2002 55"040 N, 126"570 WRock 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 WIII. 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 PacificCannery(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

62 Nat Hazards (2009) 48:59–72

123

Travel angles of landslides discussed below are plotted in Fig. 2. The travel angle, ameasure of the vertical difference of the lowest and highest points on a landslide (H) as aratio 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 toa minimum of 9.9" for rock slides that entrain soil.

Fig. 2 Plot of landslide runout(height over length (H/L)) versusvolume for select landslides inwest central BC. Note the lowH/L ratios for glaciomarinelandslides

Table 1 continued

Numberon map

Landslide name Date Latitude/longitude Infrastructureimpacted

Debris flow

27 Hotspring 1978 54"100 N, 129"520 W28 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

35 Telkwa River Ongoing 54"380 N, 127"250 WFlowslide–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

Washout-flow

42 Tchesinkut Creek Historic 54"080 N, 125"500 WNon-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

Nat Hazards (2009) 48:59–72 63

123

The landslides damage infrastructure in two main ways. (1) Most commonly infra-structure 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 themain body of the landslide moves. Where rock slides, debris flows, and debris slidesdescribed 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 flowslidesdamaged infrastructure located in the zone of depletion by carrying it along duringmovement. See Cruden and Varnes (1996) for landslide terminology.

Landslides also can have varying causes and triggers. Examples of causes can beinherent 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 havelonger 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 occurredsince 1999, and four since 2002 (Fig. 1; Table 1). Three of the six rock slides severednatural gas pipelines. All of the rock slides had relatively long runouts with travel distancesup 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. Therock slide traveled 2.7 km, entraining till and colluvium. It ruptured a natural gas pipelineand formed a lake. The initial rockslide involved 0.9 Mm3 and the entrained volume isestimated to be 1.5 Mm3 (Schwab et al. 2003). It had a travel angle of 25.6" (Geertsemaand Cruden 2008). The initial movement involved toppling and cliff collapse onto aglacier. The debris traveled over the glacier and dropped into a steep sided valley, where itentrained 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 of16.3" (Geertsema and Cruden 2008). McDougal et al. (2006) demonstrated the importanceof entrainment of fine-grained sediment along the debris flow portion of the landslide. Anestimated 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 formore than 1 year due to the flooding of a major forest road.

The remaining rock avalanches did not damage infrastructure but occurred near areas ofpotential development. Two of these large rock slides also occurred in 2002 (Geertsemaet al. 2006a). The Harold Price and Bishop Bay landslides occurred near Smithers andsoutheast of Prince Rupert on the outer coast, respectively (Fig. 1). The Harold Pricelandslide (Fig. 3c) initiated in what appeared to be a rock glacier in a cirque basin sometimebetween 22 and 24 June 2002. Interstitial ice was found in the main scarp. After travelling1.3 km the rock slide transformed into a debris avalanche entraining till and colluvium. Thedebris avalanche channelized into a debris flow of 2.2 km from its source. The total traveldistance 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 lessprecisely dated (Geertsema et al. 2006a). It probably initiated as a rockfall. The landslide

64 Nat Hazards (2009) 48:59–72

123

traveled 1.1 km over a vertical range of 370 m and entrained sandy, bouldery till derivedfrom 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). Thelandslide impact was powerful enough to leave a seismic signal at the Fort St. Jamesseismic station. The rapid landslide traveled 1.6 km at a travel angle of 11.3" (Blais-Stevens et al. 2007) and involved 3 Mm3 of volcanic rock and soil. The landslide

Fig. 3 Large, long runout rock slides in west central BC. See Fig. 1 for locations. (a) The 1999 Howsonrock 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 channelizeddebris flow, dammed the Zymoetz River, flooded an important Forest Service Road for more than a year, andruptured a pipeline. The landslide traveled 4 km. (c) The 2002 Harold Price rock slide transformed into adebris avalanche and then into a channelized debris flow, traveling more than 4 km. (d) The 2002 BishopBay rock slide on the outer coast traveled 1.1 km. (e) The 2005 Sutherland rock slide transformed into adebris avalanche and traveled 1.6 km

Nat Hazards (2009) 48:59–72 65

123

bifurcated in the runout zone. Pre-slide deformation was evident on aerial photographs, andthe 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 typ-ically initiate in steep source areas, travel through gullies, and deposit on fans in the valleybottoms. Debris flows intergrade to debris floods (hyperconcentrated flows) and floods, withdecreasing sediment concentrations. Many fans in west central BC are the product of allthree 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 debrisflows (Fig. 4) is near Legate Creek (Fig. 1; Table 1). Two debris flows closed the highwayat 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 anearlier event in the 1920s.

Large fans at Hunter Creek (east of Kitimat), Gosnell Creek (West Houston), andSinclair creek (west of Smithers) (Fig. 1; Table 1) routinely wash out roads during floodperiods and cause considerable road maintenance issues. Debris and water floods are morecommon on these large fans than debris flows, but linear infrastructure placed on theselandforms still requires careful hydro-geomorphological assessment.

Fig. 4 A debris flow at LegateCreek (east of Terrace) crossedthe highway twice in 2004 andonce in 2007. The 2007 eventpictured here resulted in twofatalities. Photo courtesy: RalphOttens, BC Forest Service

66 Nat Hazards (2009) 48:59–72

123

3.1.3 Debris slides and avalanches

Shallow, rapid debris slides, and avalanches occur throughout west central BC but areparticularly 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 ante-cedent conditions met including soil moisture, total storm rainfall, rainfall intensity, andsnowmelt input (Jakob et al. 2006). Debris slides and avalanches close roads and rail lineson an almost annual basis and occasionally sever natural gas pipe lines and hydrotrans-mission lines (Septer and Schwab 1995).

Because the west side of the Coast Range is much wetter than the east side, moreshallow 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 asmall community north of Prince Rupert and also disrupted road and rail service. Similarlandslides removed power poles serving a small community on Porcher Island south ofPrince Rupert in 1998 and in 2001. Landslides often occur in clusters and are triggered bystorms. Major historical storms that triggered debris avalanches and flows, impacting railand more recently road transportation, occurred in the Prince Rupert area in the years of1917 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 ofHungr et al. (2001) and tend to occur only in advance phase lake sediments, buried by till

Fig. 5 Storm-triggered shallowdebris avalanches initiated duringa 2002 rainstorm in a clearcutabove the North Pacific Cannerynear Prince Rupert

Nat Hazards (2009) 48:59–72 67

123

(Geertsema et al. 2006a). The slower moving earth flows in west central BC can occur inall these materials.

Slow moving earth flows reactivated along the Morice River road following roadupgrades in the 1970s and a major wild fire in 1983. These landslides covered areas from10 ha to over 100 ha in size. Millions of dollars were spent stabilizing the slopes andrepairing a 15-km section of the road. The failures occurred in till and glaciolacustrinesediment 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, unpublisheddata). In the historic period a portion of the landslide continues to advance as a slow-moving 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 ofmovement over the past 10 years has occurred along the tower. The prehistoric landslideinvolved more than 150 Mm3 of material including colluvium derived from tuffaceousvolcaniclastic rock. Other locations within the Telkwa valley and within the volcanic rocksof 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, ahighway, and a pipeline in the western portion of the study area (Fig. 1; Table 1). Theytend 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 thatoccurred during rail bridge construction across Alwyn Creek. The landslide occurred atMile 6.6 on the Canadian National railway line between Terrace and Kitimat and wasreported in the Terrace Standard on 24 June 1953. The landslide buried bulldozers andother 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 andKitimat in May and June 1962 (Clague 1978; Geertsema and Schwab 1997). Both land-slides debouched into Lakelse Lake, carrying vehicles and equipment with them. Loading

Fig. 6 An advancing lobe of the ‘‘Bulbous Toe’’, an earth flow west of Smithers involves fine texturedcolluvium and is traversed by a hydrotransmission line (1). One of the towers requires periodic adjustment

68 Nat Hazards (2009) 48:59–72

123

from a spoil berm associated with highway construction was the likely trigger in bothcases. The landslides were not retrogressive, since they were triggered, where the highwaycrossed them, near the mid points of the zones of depletion. They involved about 11 and15 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 wasclassified by Geertsema et al. (2006b) as a retrogressive earth flow–earth spread. Thelandslide, involving 2.5 Mm3 of glaciomarine sediment, traveled 1.6 km at 1.7" (Geert-sema and Cruden 2008). The landslide dammed Mink Creek, creating a lake over 1.2 kmlong 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 crownto tip with a travel angle of 2.6" (Geertsema and Cruden 2008). The river was dammedover 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 to100 ha. A 40-ha flow along Houston Tommy Creek that occurred in the 1950s involvedmore than 15 Mm3 of material (Fig. 1; Table 1). The landslides were up to 1.2 km longwith travel angles as low as of 6.5" (Geertsema and Cruden 2008). These landslides havenot 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 gentlydipping Tertiary lava flows that cover older volcanic and sedimentary rocks and intrusiverocks of upper Jurassic and Cretaceous age. Much of the bedrock is obscured by deepglacial drift. Spreading is occurring along 2.5 and 1.3 km west facing scarps in the ParrotCreek valley involving possibly up to 150 and 50 Mm3 of material, respectively (Fig. 1;Table 1).

Fig. 7 The 2003 Khyex landslide ruptured a natural gas pipeline (arrows), disrupting service to PrinceRupert for 10 days. The landslide occurred primarily in glaciomarine sediments

Nat Hazards (2009) 48:59–72 69

123

4 Future hazard regimes

Landslides in mountainous terrain are strongly influenced by climatic factors, includingprecipitation and temperature (Evans and Clague 1994). Catastrophic landslides at highelevations may be especially responsive to increases in temperature. Researchers havesuggested that recent melting of glaciers in BC has debuttressed rock slopes adjacent toglaciers, 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 thestability of slopes (Harris et al. 2001). Recent large rock avalanches in the European Alpshave been attributed to the melting of mountain permafrost, and this phenomenon may alsoplay a role in initiating landslides in northern BC, as in the case of the Harold Pricelandslide (Fig. 3c).

The Mink Creek flowslide near Terrace occurred after nearly a decade of increasingtemperature and precipitation. Geertsema and Schwab (1997) provided evidence for anincrease in flowsliding 2,000–3,000 years ago in the Terrace area under wetter climaticconditions. Almost all global circulation models predict warmer and wetter conditions in thefuture 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 mountainpine beetle within the next decade (Eng et al. 2005). These changes to the forest areexpected to have widespread hydrological impacts to the landscape and may predisposeslopes 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 circulationmodels, generally predicting a progressively warmer and wetter climate for Terrace. The data were obtainedfrom the Canadian Institute for Climate Studies web site (http://www.cics.uvic.ca) and is modified fromGeertsema et al. (2006b)

70 Nat Hazards (2009) 48:59–72

123

5 Conclusions

Linear infrastructure is at continued risk from a variety of landslide types in west centralBC. The landslides range from shallow debris slides and flows to massive rapid, rockslides, and slow moving earth flows and rapid flowslides. The risk is likely to rise underscenarios 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 beemployed to assess slope deformation that often precedes catastrophic failure. Detailedslope deformation and runout models should continue to be developed to predict slopebehavior 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 ourmanuscript. Earlier comments from Frank Maximchuck, Gord Hunter, and Jonathan Fannin are also muchappreciated.

References

Blais-Stevens A, Geertsema M, Schwab JW, van Asch Th, Egginton VN (2007) The 2005 Sutherland Riverrock slide–debris avalanche, central British Columbia. In: 1st International landslide conference, Vail

Boultbee N, Stead D, Schwab JW, Geertsema M (2006) The Zymoetz River rock avalanche, June 2002,British Columbia, Canada. Eng Geol 83:76–93

Clague JJ (1978) Terrain hazards in the Skeena and Kitimat River basins, British Columbia. GeologicalSurvey of Canada Paper 78-1A, pp 183–188

Clague JJ (1984) Quaternary geology and geomorphology, Smithers-Terrace-Prince Rupert area, BritishColumbia. Geological Survey of Canada, Memoir 413, 71 pp

Cruden DM, Varnes DJ (1996) Landslide types and processes. In: Turner AK, Schuster RL (eds) Specialreport 247: landslides investigation, mitigation. National Research Council, Transportation ResearchBoard, Washington D.C., pp 36–75

Duffel S, Souther JG (1964) Geology of the Terrace map-area, British Columbia (103 I E 1/2). GeologicalSurvey of Canada, Memoir 329

Egginton VN (2005) Historical climate variability from the instrumental record in northern British Columbiaand its influence on slope stability. M.Sc. thesis, Simon Fraser University, Burnaby, 130 pp

Eng M, Fall A, Hughes J, Shore T, Riel B, Hall P, Walton A (2005) Provincial level projection of the currentmountain pine beetle outbreak: an overview of the model (BCMPB v2) and results of year 2 of theproject. Ministry of Forests Report, 51 pp

Evans SG, Clague JJ (1994) Recent climatic change and catastrophic geomorphic processes in mountainenvironments. Geomorphology 10:107–128

Geertsema M, Cruden DM (2008) Travels in the Canadian Cordillera. In: Locat J, Perret D, Turmel D,Demers D, Leroueil S (eds) Proceedings of 4th Canadian conference on geohazards, Quebec City,pp 383–390

Geertsema M, Schwab JW (1997) Retrogressive flowslides in the Terrace-Kitimat, British Columbia area:from early post-deglaciation to present and implications for future slides. In: Proceedings of 11thVancouver geotechnical society symposium, Vancouver, pp 115–133

Geertsema M, Torrance JK (2005) Quick clay from the Mink Creek landslide near Terrace, BritishColumbia: geotechnical properties, mineralogy, and geochemistry. Can Geotech J 42:907–918

Geertsema M, Clague JJ, Schwab JW, Evans SG (2006a) An overview of recent large catastrophic landslidesin northern British Columbia, Canada. Eng Geol 83:120–143

Geertsema M, Cruden DM, Schwab JW (2006b) A large rapid landslide in sensitive glaciomarine sedimentsat Mink Creek, northwestern, British Columbia, Canada. Eng Geol 83:36–63

Harris C, Davies MCR, Etzelmuller B (2001) The assessment of potential geotechnical hazards associatedwith mountain permafrost in a warming global climate. Permafr Periglac Process 12:145–156

Holland SS (1976) Landforms of British Columbia. British Columbia Department of Mines and PetroleumResources, Bulletin 48, 138 pp

Holm K, Bovis MJ, Jakob M (2004) The landslide response of alpine basins to post-Little Ice Age glacialthinning and retreat in southwestern British Columbia. Geomorphology 57:201–216

Nat Hazards (2009) 48:59–72 71

123

Hungr O, Evans SG, Bovis MJ, Hutchinson JN (2001) Review of the classification of landslides of the flowtype. Environ Eng Geosci 7:221–238

Jakob M, Holm K, Lange O, Schwab JW (2006) Hydrometeorological thresholds for landslide initiation andforest operation shutdowns on the north coast of British Columbia. Landslides 3. doi:10.1007/s10346-006-0044-1

Mathews WH (1986) Physiographic map of the Canadian Cordillera. Geological Survey of Canada,Map 1701A

McDougal S, Boultbee N, Hungr O, Stead D, Schwab JW (2006) The Zymoetz River landslide, BritishColumbia, Canada: description and dynamic analysis of a rock slide–debris flow. Landslides 3:195–204

Meidinger DV, Pojar JJ (1991) Ecosystems of British Columbia. B.C. Ministry of Forests Special ReportSeries, no. 6, 330 pp

Schwab JW (2002) Dendrochronology of debris flows on British Columbia north coast districts. In: JordanP, Orban J (eds) Terrain stability and forest management in the interior of British Columbia: workshopproceeding May 23–25, 2001. Nelson British Columbia Canada. Research Branch, British ColumbiaMinistry of Forests, Victoria, B.C. Technical Report 003, p 217

Schwab JW, Kirk M (2003) Sackungen on a forested slope, Kitnayakwa River. British Columbia Ministry ofForests, Prince Rupert Forest Region. Extension Note 47, 6 pp

Schwab JW, Geertsema M, Evans, SG (2003) Catastrophic rock avalanches, west-central B.C., Canada. In:3rd Canadian conference on geotechnique and natural hazards, Edmonton, AB, pp 252–259

Schwab JW, Blais-Stevens A, GeertsemaM (2004a) The Khyex River flowslide, a recent landslide near PrinceRupert, British Columbia. In: 57th Canadian geotechnical conference, Quebec City, 1C, pp 14–21

Schwab JW, Blais-Stevens A, Geertsema M (2004b) The Khyex River landslide of November 28, 2003,Prince Rupert British Columbia, Canada. Landslides 1:243–246

Septer D, Schwab JW (1995) Rainstorm and flood damage: Northwest British Columbia 1891–1991. B.C.Ministry of Forests, B.C. Land Management Report 31, 196 pp

Wilford DJ, Sakals ME, Innes JL (2003) Forestry on fans; a problem analysis. For Chron 79:291–296

72 Nat Hazards (2009) 48:59–72

123