1

The Use of Dendrochronology to Determine Avalanche

Frequency Along the Avalanche Path East of Balu Peak, Within

the Balu Pass Trail, Roger's Pass, BC.

Allison Dick, Donald Mcfarlane, and Robyn McGregor

Geography 477: Field Studies in Physical Geography

Instructor: Dan Smith

University of Victoria: Department of Geography

December 2011

2

Abstract

Glacier National Park in British Columbia is an area of steep mountainous terrain and heavy

snowfall. This results in frequent avalanche activity which can lead to the destruction of property and the

loss of human life. Research focused on determining the potential for avalanches and the frequency of

avalanche events can help to mitigate this risk. Dendrochronology (the study of tree rings), can be used as

a basis for this research. By analyzing a specific avalanche path along the Balu trail in Glacier National

Park using dendrochronological techniques, an avalanche history could be determined. This information

was then used in conjunction with weather station climate data to attempt to ascertain an avalanche

activity pattern, and hopefully aid in the prediction of future avalanche events.

3

Table of Contents

Abstract ..............................................................................................................................................2

Table of Contents …...........................................................................................................................3

List of Figures …................................................................................................................................3

List of Tables ….................................................................................................................................4

Acknowledgements ….......................................................................................................................5

1. Introduction…....................................................................................................................(6)

1.1 Introduction....................................................................................................................(6)

1.2 Background - Glacier National Park .............................................................................(7)

1.3 Avalanche Characteristics ….........................................................................................(8)

1.4 Avalanche Risk ….........................................................................................................(10)

1.5 Dendrochronology …....................................................................................................(11)

2. Site Area …........................................................................................................................(13)

2.1 The Balu Pass Tail …...................................................................................................(13)

2.2 Study Site …................................................................................................................(13)

3. Methodology …..................................................................................................................(15)

3.1 Data Collection and Analysis …...................................................................................(15)

3.2 Dendrochronology …....................................................................................................(15)

3.3 Weather and Climate …................................................................................................(16)

3.4 Event-response Index …...............................................................................................(17)

4. Results …............................................................................................................................(17)

4.1 Tree Ages.......................................................................................................................(17)

4.2 Event Response Index....................................................................................................(18)

4.3 Snowpack.......................................................................................................................(19)

4.4 Precipitation and Temperature ......................................................................................(20)

4.5 Tables of Results ...........................................................................................................(22)

4.6 Slope Reconstruction .....................................................................................................(25)

5. Discussion ….......................................................................................................................(25)

6. Conclusion …......................................................................................................................(26)

7. References ….......................................................................................................................(28)

List of Figures

Figure 1.3.1 Typical Avalanche Debris in Run Out Zone.................................................................(10)

Figure 1.5.1 Sub Alpine Fir with External Scars .............................................................................(11)

Figure 1.5.2 Tree disc with evidence of reaction wood.....................................................................(12)

4

Figure 2.2.1 View of Avalanche Path..........................................................................................(14)

Figure 3.2.1 Example of Increment Borer..................................................................................(15)

Figure 4.1.1 Tree Ages...............................................................................................................(18)

Figure 4.2.1 Event Response Index............................................................................................(19)

Figure 4.3.1 Snow depth vs annual potential avalanche evidence.............................................(19)

Figure 4.4.1 Precipitation as rain vs annual potential avalanche activity................................(20)

Figure 4.4.2 Temperature Variations vs Annual Potential Avalanche Activity.........................(21)

Figure 4.6.1 Generalized Model of Slide Site Terrain...............................................................(25)

List of Tables

Table 4.5.1 Minor, Moderate, and Major events as determined by Lab Analysis of Tree Ring Samples (22)

Table 4.5.2: Maximum and Minimum Temperatures and Precipitation by Year........................(23)

Table 4.5.3: Snowpack data........................................................................................................(24)

5

Acknowledgements:

First and foremost, we would like to thank Dr. Dan Smith and Dr. James Gardner for an inspiring

and valuable field school experience. We would also like to express our sincere gratitude to Kara Pitman

for her guidance and assistance throughout the research phase of this report, and Bethany Coulthard and

Jodi Axelson for their technical expertise and unending support. We would also like to thank Parks

Canada for providing a pristine backdrop for our research endeavours.

6

1. Introduction

1.1 Introduction

Snow avalanches are an inherent natural process in mountainous environments. Avalanche

potential is influenced by terrain and climatic processes, and they can be triggered naturally or by human

activity. In British Columbia, Canada, Glacier National Park is an area that receives a great deal of snow

throughout the winter months, as well as many backcountry visitors (Parks Canada, 2011b). The steep

and rugged mountains that are found in the park contribute to its renowned natural beauty, however they

also contribute to the danger associated with backcountry travel during the winter months.

The Balu Pass Trail is a highly popular area used by backcountry travelers throughout the winter.

The terrain surrounding the trail has been classified as complex avalanche terrain by Parks Canada, and

this poses a great deal of risk for any area users. There are numerous avalanche tracks along the trail, and

a specific one was chosen to investigate avalanche activity by using dendrochronological analysis.

Dendrochronology, the study of tree dating and tree ring analysis, is commonly used as a tool to

determine avalanche frequency and magnitude. Past avalanche events are recorded in the tree ring

succession as distinct darker and wider rings. These rings can be dated and then cross referenced against

climate data to determine the climactic influences necessary in the development of avalanche conditions.

The purpose of this study was to investigate the relationship between climatic data and avalanche

frequency for a specific avalanche track along the Balu Pass Tail in Glacier National Park. This study

sought to determine if dendrochronology can be used as a predictive method for avalanche risks, based

upon the trends and cycles of avalanche activity in previous years.

7

1.2 Background - Glacier National Park

Glacier National Park, established in 1886 with the completion of the transcontinental Canadian

Pacific Railway, lies within the Selkirk and Purcell Ranges of the Columbia Mountains of southeastern

British Columbia. Within Glacier National Park Rogers Pass National Historic site, which commemorates

this significant and perilous link of the Canadian Pacific Railway, is located at the summit of the Trans

Canada Highway corridor. The highway was completed in 1962, and since then recreational tourism has

increased dramatically throughout the year (Parks Canada, 2011a). Glacier National Park was the second

national park to be created in Canada, and the first in British Columbia.

The park itself is a rugged and steep mountainous landscape capped by numerous glaciers, and

covers a total area of 1,350 km2. Glacier National Park is a diverse environment that has three distinct

‘life zones’ that are mostly governed by elevation. The zones are characterized as, from lowest to highest

elevation; interior rainforest, subalpine life zone, and no forest zone (Parks Canada, 2011b). These

distinctly different zones create the diverse mosaic of habitats that are home to a wide variety of

organisms, including many threatened and endangered species.

The climactic conditions of the park are characteristic of the Columbia Mountains. High annual

precipitation, heavy rains in the summer and deep snow pack in the winter, is caused by the wet and mild

westerly air masses that are intercepted by the Columbia Mountains. Like any other steep and

mountainous environment with a deep winter snow pack, there is a high risk and occurrence of

avalanches. Along the Trans Canada Highway, avalanches are so abundant that a special team, the Rogers

Pass Mobile Avalanche Control Program, was created to manage slopes that could be hazardous to those

using the highway. The Rogers Pass Avalanche Control Program is the largest of its kind in the world,

and this can attest to the severity of risk that is posed by the terrain and its deep snow pack. Parks Canada

avalanche forecasters release a public avalanche bulletin every day to report the current avalanche risk

within the given area (Parks Canada, 2011b).

Many recreational tourists use the park trails throughout the year, and in recent decades ski

touring has become an increasingly popular winter activity in the park. The park tails cross and intersect

8

numerous avalanche paths, and this poses a high level of risk for winter users. Much of the park’s terrain

is classified as complex avalanche terrain; this means that avalanches will happen often and can be of

disastrous magnitudes (Parks Canada, 2011c). Though avalanche and snowpack information for the area

is well documented, the terrain is not controlled like it is in ski resorts, and avalanche fatalities have

occurred in the past. Having an understanding of the frequency and magnitude of avalanches on given

slopes is a key tool that can be used to make decisions in the backcountry. There currently is a lack of

information regarding frequency and magnitude of avalanches on specific slopes that intersect trails

within the park. For this reason tree ring data was collected on the Balu Pass Trail, a popular ski touring

trail, and dendrochronological analysis was used to determine the frequency of avalanches on a specific

slope.

1.3 Avalanche Characteristics

A snow avalanche is a rapid down slope release of a mass of snow. They can be highly

destructive to natural and manmade features, and dangerous to those who travel through, or spend time

within, avalanche zones. Of particular interest, due to their destructive capabilities, are slab avalanches

(Jamieson, 2004). Slab avalanches are responsible for the majority of avalanche related fatalities within

North America. According to the Canadian Avalanche Centre (2011), these occur on slopes that are

generally between 25 and 45 degrees and can be formed by wet or dry snow, storm snow events, or

consistent deposition of snow via wind. In each case, a mass of snow is sheared from an underlying

surface due to the presence of a weak layer (or weak interface) within the snowpack. These shearing

points are most often caused by the development of weak interfaces (sun crusts and rain crusts) or a weak

layer (faceting and surface hoar). Sun crusts form when an increase in solar radiation results in a surficial

melting of the snow layer. As temperatures decrease, this melted layer refreezes and acts as a

destabilizing point for the snow mass. Similarly, increased temperatures may result in precipitation falling

as rain. This saturates the snow surface, which then freezes, creating a shear and icy surface. Surface hoar

occurs during clear and calm nights; snow radiates a great deal of heat that accumulates during the day

9

and in doing so the snow surface becomes very cold. This warm supersaturated air sits above the snow

surface. The water vapour then condenses as it cools onto the snow surface and forms fine ‘feather-like’

icy crystals. This is simply the winter equivalent of dew. Faceting, which is a process that builds angular

grains (facets) in the snowpack that bond poorly to one another and other grains present in adjacent

layers, are formed by strong temperature gradients in the snowpack. When a strong temperature gradient

is present in the snowpack (>1 degree / 10cm), water vapour moves rapidly from warm grain surfaces to

colder ones. Since snow is an excellent insulator the temperature at the bottom of the snowpack is

relatively warm (at or near 0 degrees C), and cools towards the snow surface. When there is a large

temperature gradient within the snowpack, water vapour from the warmer layers wants to move from

areas of high concentration to areas of low concentration (the colder snow layers). As the water vapour

diffuses rapidly through the snowpack, it changes rounded crystals into faceted ones. In other words, this

changes the affected snow from strong cohesive snow, to weak non cohesive snow (Temper, 2010). In

each case, the snow mass is destabilized until an avalanche is triggered. Triggers can be natural (mass

becomes too great and gravity triggers release of avalanche) or human induced (snowmobilers

“highlining”, or backcountry skiers traversing across the potential avalanche zone). Once triggered, the

snow mass then travels down an avalanche path until velocity is lost and mass is deposited (Canadian

Avalanche Centre, 2011).

The avalanche path is defined by three zones: the starting zone, the track zone, and the run-out

zone (Johnston & Jamieson, 2011). Snow is accumulated in the starting zone until the unified mass

reaches a failing point and begins to travel down slope through the track zone. As the snow mass

descends, it gains velocity and debris before reaching the run-out zone (an area of lower slope angle)

where the snow and debris is deposited (Canadian Avalanche Centre, 2011). The avalanche path chosen

for this study is confined in its run-out zone by an uphill slope on the opposite side of the valley. The

result is a dense collection of debris deposited at the valley bottom.

10

Figure 1.3.1 Typical Avalanche Debris in Run-out Zone

1.4 Avalanche Risk

The study of avalanches in populated and recreational areas is important in order to protect the

safety of all area users. In Glacier National Park, backcountry skiers and recreational users must be aware

of the inherent avalanche risks, and rely on reports from Parks Canada and the Canadian Avalanche

Association to help them make informed decisions. While these organizations provide detailed and

accurate reports on conditions, tragedies do still occur. In 2003, 17 students were caught in an Avalanche

along the Balu trail in Glacier National Park during a back country skiing expedition. 7 did not survive

(Canadian Broadcasting Corporation, 2003). It was an eye opening event, and one that highlighted and

reaffirmed the risks associated with recreational use in mountainous areas. According to the CBC news

article (2003), the students and trip coordinators were aware of the avalanche risk rating of considerable,

11

indicating a possibility of avalanches, yet due to their considerable expertise within the group, decided to

proceed.

1.5 Dendrochronology

One of the many tools available to those interested in studying avalanches is determining the

magnitude and frequency of events as recorded by changes in tree ring characteristics. Dendrochronology

utilizes either an increment borer, which extracts a sample core of the tree rings without harming the

individual, or by sawing discs from the base of the tree. The latter, unfortunately, does result in the death

of the individual tree. The rings may be later analyzed in a lab setting to determine the age and climactic

controls acting upon the tree. There are two features that are of particular interest in using

dendrochronology to study avalanche frequency and magnitude: scars and reaction wood. Scars are

formed when debris or snow is dragged along a tree in an event such as a snow avalanche, leaving a

marked scar on the tree’s bark. By backdating on a core or a disc taken at the scar sight from the scar to

the pith, one can determine the date of the scar in relation to the tree’s total age.

Figure 1.5.1 Sub Alpine fir with Scars

12

Unlike the external evidence of scars, reaction wood is recorded within the tree rings, and is

therefore accessed using increment borers or by slicing discs from the tree. Reaction wood forms when an

event causes the tree to bend, such as from the force of an avalanche. As the tree continues to grow, it

attempts to realign and become once again erect. This results in a marked and noticeable change in the

tree ring pattern – reaction wood is characterized by wider and darker rings on the increment borer cores,

and is shown as a distinctive pattern on tree discs (figure 1.5.2). Reaction wood can be caused by a

multitude of events, such as rockfalls, high winds, or even heavy snowpack. Therefore, cross referencing

samples for years of distinct reaction wood occurring in a controlled area is necessary to determine the

cause of the reaction wood.

Figure 1.5.2 Tree disc with evidence of reaction wood

Both the discs and the cores are analyzed under microscope in a lab setting, and tree rings are

counted to determine total age of the tree and years of scars or reaction wood evidence. As samples are

cross referenced to each other, a chronology may begin to emerge that highlights the avalanche frequency

and history along the chosen path.

13

2. Study Area

2.1 The Balu Pass Trail

The trailhead for the Balu Pass Trail is located behind the parking lot of the Rogers Pass

Discovery center, which makes this trail easily accessible and very popular among visitors. The Balu Pass

Trail is a 6.4 km hike up to the Balu Summit, which passes through stands of Mountain Hemlock (Tsuga

mertensiana) and Englemann spruce (Picea engelmannii), numerous avalanche run-out zones, and finally up

into the alpine meadow and wetland area near the summit. The trail gets its name from the First Nations’

word “baloo”, meaning bear, and as the name suggests the terrain along this trail is prime bear habitat

(Parks Canada, 2011d). The possibility of bear sightings throughout the spring, summer, and autumn

months attracts many visitors in spite of the inherent dangers of bear sightings. This is not the only

dangerous and exciting attraction that entices visitors to journey off the highway; in the winter months the

deep snowpack and steep terrain of Balu Pass Trail attracts ever-increasing numbers of backcountry skiers

and snowboarders. The terrain surrounding the trail has been classified by Parks Canada, as complex

avalanche terrain. Complex avalanche terrain is described as, “exposure to multiple overlapping

avalanche paths or large expanses of steep, open terrain; multiple avalanche starting zones and terrain

traps below; minimal options to reduce exposure. Complicated glacier travel with extensive crevasse

bands or icefalls” (Parks Canada, 2011c). Since the terrain surrounding the trail is so dynamic, steep, and

complex the risk of avalanche activity throughout the Balu Pass area is high.

2.2 The Study Area

The avalanche path that was selected for study is located approximately 4 km from the head of

the Balu Valley Trail in Glacier National Park (51°17’25”N, 117°34’12”W) with an elevation at the trail

of approximately 1800m (Google Earth, 2011). It was chosen for its ease of access to vegetation, as well

as a clearly delineated avalanche path. The main vegetation on the avalanche path was Subalpine fir

(Abies lasiocarpa) and Aspen.

14

Since the terrain surrounding the trail is classified as complex avalanche terrain, there are

numerous avalanche tracks that intersect the trail and pose risk for winter trail users (Parks Canada,

2011c). The track that was chosen for this study because it intersects the trail on a steep slope, which is

very exposed. The study site is also a run-out zone for the Bruins Pass area, which is very popular among

backcountry skiers and snowboarders due to its slightly more ‘manageable’ terrain.

The trees that were sampled from the track were all Subalpine fur (Abies lasiocarpa). The height

and age of the sampled trees varied; however the younger and smaller trees tended to be located closer to

the center of the avalanche track, where as the older and larger trees tended to be further away from the

center. There was a great deal of evidence from past avalanches on the living trees. This included

extensive scarring, trunk deformation, and stripped off uphill branches on the main stem of trees. There

was also an abundance of Alder shrubs throughout the study area. These features can be used in

conjunction with a dendrochronological reconstruction of avalanche activity to assess the frequency of

avalanches along the selected avalanche track.

Figure 2.2.1 View of Avalanche Path

15

3. Methodology

3.1 Data Collection and analysis

Field data collection was primarily focused on vegetative evidence, with some data compiled for

a topographic reconstruction of the avalanche slope. Slope data was found using a digital range finder to

determine the angle of slope in the accumulation, track, and run-out zone of the avalanche path. This data

was later used to create a generalized model of the underlying terrain.

3.2 Dendrochronology

In order to determine the frequency of large avalanche events, tree cores and discs were taken

from vegetation along the North East section of the avalanche path. In the accumulation zone, tree core

samples were taken from individuals with visible markings and scars, all of which were Subalpine firs.

Samples were discarded if they did not reach the pith of the tree. Tree cores were taken with a 5mm

increment borer. The samples were taken low to the ground (approximately breast height) to ensure the

maximum presence of tree rings, in order to establish the most accurate dates

Figure 3.2.1 Example of Increment Borer

16

In the track zone, discs were sawed from Subalpine firs, with an emphasis placed on trees that

exhibited scarring, potential reaction wood, and trees that had branches stripped off on the uphill side of

the main stem. The discs were taken throughout the length, as well as laterally from the center of the

avalanche path, for potential determination of the magnitude of the avalanche events. The samples were

then taken back to the University of Victoria Tree Ring Lab for further analysis.

The tree core samples were glued and mounted to boards, sanded (using six different grades of

sandpaper), and analyzed under a microscope to determine the age of the tree as well as dates of

avalanche evidence in the form of reaction wood and scars. Rings were counted inward from the bark

with an error margin of +/- two years. Scars and dark, wide rings (reaction wood) were noted as years of

potential avalanche activity. Similarly, discs were sanded and years were counted inward from the bark to

determine total age, year of reaction wood, and year to which a scarring event occurred. All findings were

compiled into a spreadsheet for graphing and cross referencing of the results.

3.3 Weather and Climate

For weather and climate data, nearby weather stations (Mt. Abbot Station (2A14) and Glacier

Station (2A02) – Water Stewardship Division of British Columbia) were used to determine the historical

snowpack data in the area. These sites were chosen based on their proximity to the study site. Data was

graphed for the years of 1959 – 2011, as these stations did not contain recorded climactic data earlier then

1959. Snow depth data was retrieved from each station and plotted against the number of times reaction

wood and scars were recorded for each year, in the hopes of discovering an emerging trend. Similarly,

climate data was collected from the Glacier National Park, Rogers Pass weather station (Environment

Canada) where temperature and total precipitation fallen as rain (mm) was recorded for each month from

1965 – 2007. The monthly rainfall, and minimum and maximum temperatures for November through

February for each year were averaged and graphed against the number of times reaction wood and scars

were present within the sample set for each year.

17

Precipitation, snow pack, temperature, and temperature variation are considerable factors in

determining seasonal avalanche risk. These parameters were chosen in an attempt to highlight the main

climactic controls that determine the conditions for avalanche formation. In winter seasons with high

fluctuations of temperatures, rain crusts, and sun crusts are likely to occur. Likewise, in seasons of

uncharacteristically cold temperatures, faceting and surface hoar are likely to occur. It is therefore

necessary to study many weather and climactic phenomena when determining avalanche risk.

3.4 Event-response Index

An event-response index (ERI) was determined by dividing the total number of reactions

recorded using dendrochronology within a year by the number of samples collected within that year,

multiplied by 100 (Schweingruber, 1988). This index was created to help delineate the avalanche event’s

magnitude and frequency (Johnson, & Smith, 2010). The minimum ERI value used to determine the high

magnitude events is a value determined by the studier with respect to the site understudy (Butler, et al.,

1987). Snow avalanche frequency was determined by subtracting the date of the earliest high-magnitude

avalanche event (based on the minimum ERI value) by the sampling year, and divided by the total

number of high-magnitude avalanche events (Johnson, & Smith, 2010).

4. Results

4.1 Tree Ages

Our sampling resulted in 111 years of usable data with 150 events of scars and, or reaction wood

recorded within the samples (with an error of +/- two years). The age of the trees within the study area

ranged from 45 to 350 years of age

18

Figure 4.1.1 Tree Ages

4.2 Event Response Index

High magnitude events were determined by using a minimum index value of 25%. This value was

determined by taking the number of years that displayed a higher incidence of reaction wood and

scarring, divided by the number of samples and multiplied by 100. From the minimum ERI value, it was

established that four or more incidence of reaction wood or scars within the sample set show a moderate

to major event occurring, while detection of three reaction wood or scars within the sample set show a

minor event, both having an error of + / – two years. The moderate to major events necessitate attention

because they would be responsible for doing the largest amount of damage, while potentially being the

most fatal. By subtracting the date of the earliest high-magnitude avalanche event (based on the minimum

ERI value) by the sampling year, divided by the total number of high-magnitude avalanche events

(Johnson, & Smith, 2010), the recurrence interval for this study area was determined to be approximately

9.5 years.

0

50

100

150

200

250

300

350

Age

(ye

ars)

Field Samples from lowest altitude to highest altitude

Age of Tree Core and Ring Samples from Avalanche Site, Balu Trail, Roger's Pass, BC

19

Figure 4.2.1 Event Response Index

4.3 Snowpack

The results show that the events are generally following a similar trend when compared to snow

pack depth throughout the years, where heavier snowfall events commonly resulted in larger avalanche

events.

Figure 4.3.1 Snow depth vs annual potential avalanche evidence

0

1

2

3

4

5

0

50

100

150

200

250

300

350

19

59

19

61

19

63

19

65

19

67

19

69

19

71

19

73

19

75

19

77

19

79

19

81

19

83

19

85

19

87

19

89

19

91

19

93

19

95

19

97

19

99

20

01

20

03

20

05

Nu

mb

er

of

Re

acti

on

Wo

od

an

d S

cars

Sno

w D

ep

th (

cm)

Year

Relationship Between Average Annual Snow Depths and Reaction Wood / Scars Found in Each Year Along the Balu Trail, Roger's

Pass, BC, 2011

Number of reaction wood and scars

Average Snow Depth from Mt Abbot and Glacier weather stations

20

4.4 Precipitation and Temperature

The results from the precipitation and temperature data follow very closely to that of the snow pack

depth data. The moderate to major events occurred during years with increased amounts of rainfall,

although a considerable amount of variability is present from 1970 to 1980

Figure 4.4.1 Precipitation as rain vs annual potential avalanche activity

0

1

2

3

4

5

6

0

5

10

15

20

25

30

35

40

Imp

act

Scar

s an

d R

eac

tio

n W

oo

d (

# o

f t

ime

s)

Pre

cip

itat

ion

fal

len

as

Rai

n (

mm

)

Year

Average Precipitation Fallen as Rain from November to February, 1965-2007 in Relation to the Number of Times Reaction Wood or Scars were

Present

Average Rainfall (mm) Number of reaction wood and scars recorded

21

The moderate and major events also occurred during the years with larger temperature variations, and

temperatures rising above freezing for those years

Figure 4.4.2 Temperature Variations vs Annual Potential Avalanche Activity

Two other minor events were detected based on the number of times reaction wood and scars were

present in 1906 and 1939, and one major event was detected in 1954. There is less evidence of avalanche

activity in the earlier years due to 35% of our samples being under 80 years of age. All event magnitudes

and dates from 1900 to 2011 are displayed in table 4.5.1, although event certainty is not as high from

1900 to 1958 due to the lack of weather information available for those years.

With our sample size, a definitive trend is not clearly displayed but based on our data and climatic

analysis the major events occur within 10, 14, and 16 years, which with further research and added

sampling, a definitive trend could emerge.

22

4.5Tables of Results

Table 4.5.1: Minor, Moderate, and Major events as determined by Lab Analysis of Tree Ring Samples

Order

of

Events

Year # of Reaction

wood and

scars present

within the year

Major,

Moderate, or

Minor Events

Time

between

events

(years)

Time between

Moderate to

Major Events

(years)

1 1906 3 Minor 0 -

2 1939 3 Minor 33 -

3 1954 5 Major 15 0

4 1968 4 Moderate to

Major

14 14

5 1971 3 Minor 3 -

6 1974 3 Minor 3 -

7 1976 3 Minor 2 -

8 1979 3 Minor 3 -

9 1984 4 Moderate to

Major

5 16

10 1988 4 Moderate to

Major

4 4

11 1989 5 Major 1 1

12 1993 3 Minor 4 -

13 1998 3 Minor 5 -

14 1999 4 Moderate to

Major

1 10

15 2000 3 Minor 1 -

16 2004 3 Minor 4 -

23

Table 4.5.2: Maximum and Minimum Temperatures and Precipitation by Year

Average Maximum and Minimum Temperatures and Rainfall by Year

Year

Average Max. Temp.

(oC)

Average Minimum

Temp.

Average Rainfall

(mm)

1965 3.6 -19.7 21.5

1966 2.2 -19.15 1.2

1967 1.275 -19.33 2.3

1968 2.225 -25.98 20.3

1969 0.15 -21.13 8.6

1970 1.95 -23.5 0.0

1971 -0.125 -22.5 9.5

1972 0.425 -26.13 0.2

1973 1.675 -23.2 5.4

1974 2.075 -19.45 11.2

1975 2.075 -26.13 33.7

1976 1.275 -20.43 9.0

1977 1 -22.78 0.0

1978 0.4 -25.03 19.5

1979 -0.5 -23.25 11.1

1980 2.625 -24.13 36.1

1981 2 -20.63 5.7

1982 0.5 -24.63 3.4

1983 1.125 -19.75 16.2

1984 0.25 -24.5 15.5

1985 -0.75 -28.63 1.3

1986 2.125 -20.38 17.7

1987 2 -20.13 12.9

1988 2 -22.88 14.2

1989 2 -22 34.4

1990 1.375 -23.5 30.5

1991 1.5 -17.38 10.6

1992 1.125 -18.5 4.4

1993 0.375 -24.13 2.4

1994 0.875 -20.88 1.7

1995 2.25 -22.88 20.7

1996 0.75 -28.63 9.3

1997 1.5 -19.25 4.1

1998 2 -22 6.5

1999 1.25 -16.13 24.3

2000 -0.125 -17.38 0.0

2001 1.25 -19.13 17.2

2002 1.25 -18.25 17.4

2003 0.375 -19.25 2.5

2004 2 -20.63 13.9

2005 2.375 -21.5 36.2

2006 1.25 -19 15.6

24

Snowpack Data from Two Nearby Weather Stations

Year Mt Abbot Snow Pack Data (cm) Glacier Snow Pack Data (cm) Average Snow Depth (cm)

1959 290 190 240

1960 257 142 199.5

1961 262 160 211

1962 282 183 232.5

1963 234 137 185.5

1964 290 175 232.5

1965 251 150 200.5

1966 315 206 260.5

1967 371 249 310

1968 274 157 215.5

1969 254 147 200.5

1970 229 142 185.5

1971 275 193 234

1972 312 221 266.5

1973 257 157 207

1974 386 201 293.5

1975 259 185 222

1976 320 188 254

1977 157 122 139.5

1978 229 145 187

1979 198 138 168

1980 230 150 190

1981 205 133 169

1982 305 187 246

1983 216 143 179.5

1984 269 160 214.5

1985 188 130 159

1986 282 194 238

1987 211 148 179.5

1988 258 140 199

1989 264 144 204

1990 319 192 255.5

1991 310 184 247

1992 259 187 223

1993 166 118 142

1994 227 153 190

1995 224 128 176

1996 307 200 253.5

1997 252 185 218.5

1998 254 156 205

1999 357 200 278.5

25

2000 284 157 220.5

2001 151 111 131

2002 282 143 212.5

2003 198 134 166

2004 243 126 184.5

2005 235 173 204

2006 244 141 192.5

Table 4.5.3: Snowpack data

4.6 Slope Reconstruction

Using the digital rangefinder, it was determined that the slope varied from 14 to 28.8 degrees,

placing a majority of the slope within the parameters of a potential slide site.

Figure 4.6.1 Generalized Model of Slide Site Terrain

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5. Discussion

While it was hoped that a cyclical trend would emerge that would aid in the prediction of

avalanche events, our results do highlight the relationship between multiple climactic controls and

avalanche activity. The graphed results of temperature variation, snowpack, and precipitation show

anomalous weather patterns leading to increased avalanche events. In years with high precipitation, and

therefore high snowpack, multiple avalanche events are often recorded. Similarly, years with high

temperatures and marked temperature fluctuations, avalanche activity appears to increase. In 1968, for

example, temperature fluctuations were high, with a change of 28 degrees C between November and

February. In that same year, 4 potential avalanche events were recorded. Similarly, 1989 saw 34.5 mm of

rainfall, and a 24 degree C temperature fluctuation. 5 potential events were recorded for this year.

Conversely, 1970 received 0mm of rain, and only one potential avalanche event. 2003 received low

precipitation, fewer temperature fluctuations, and a low snowpack. As a result, one potential event was

recorded.

When recording reaction wood, it was important to make note that reaction wood is not only

caused by avalanches. Rock falls, soil creep, extreme weather, and even a heavy snow pack can all result

in reaction wood formation. It is difficult to discern avalanche activity, and assuming that each year of

reaction wood recorded is an avalanche event leads to a potential for erred results.

Additional sources of error included a lack of equipment in the field. GPS units and tape

measures would have allowed for a more detailed spatial analysis of the distribution of scars and instances

of reaction wood. This would aid in determining the extent of avalanche activity.

In the lab setting, due to the inexpertise of the users, some error was introduced in counting rings,

scars, and reaction wood incorrectly.

6. Conclusion

Despite the previously mentioned errors, some conclusions may be drawn based upon our data

and research. Our original research question asked “can dendrochronology be used as a predictive method

27

for avalanche risks, based upon the trends and cycles of avalanche activity in previous years?”. It was

concluded that dendrochronology may be a very effective predictive technique, but the scope and

limitations of this particular research project did not yield a definitive trend and therefore was unable to

make predictions for the particular slide site. It was also hypothesized that analyzing multiple climactic

controls is necessary to determine avalanche potential. It was found that there was no singular climactic

control that lead to high avalanche event years, but rather each climate factor studied (precipitation,

temperature, temperature variations, and snowpack) contributed to years of assumed avalanche events.

Given the scope of Canada’s mountainous regions, it is difficult to make detailed information

available about specific and small scale backcountry areas. The resources necessary for

dendrochronological studies at this small of a scale along the entire Balu Pass recreation area would be

staggering. However, site specific data concerning weather conditions is readily available to the public.

Our research highlights the relationship between climate and avalanche frequency, which helps to

reinforce the need for backcountry users to be aware of the conditions of the area prior to setting out.

This increased awareness allows backcountry users to enjoy the natural splendour and beauty of rugged

mountain environments, while lessening the risk of loss of life.

28

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