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Avalanche deaths in the United States: a 45-year analysis
Wilderness and Environmental Medicine, 10, 146-151 (1999)
ORIGINAL RESEARCH
Avalanche deaths in the United States: a 45-year analysis CHARLES E. PAGE, MD; DALE ATKINS, BA; LEE W. SHOCKLEY, MD; MICHAEL YARON, MD From the Denver Health Medical Center, Division Qf Emergency Medicine (Dr Page and Dr Shockley). Ihe Colorado Avalanche Information Center, Colorado Geologic Survey (Mr AIkins). and the University of Colorado Health Sciences Center, Division of Emergency Medicine, Colorado Emergency Medicine Research Cemer (Dr Yaron).
Objective.-To describe the demographic characteristics and patterns of death of persons killed in snow avalanches over a 45-year study period. Methods.-The national avalanche database was the source of data in this retrospective, descriptive study. Results.-A total of 440 victims were killed in 324 fatal avalanches, of which 87.7% were fully buried, 4.7% were partially buried, and 7.6% were not buried. The average age was 27.6 :!: 10.6 years, and 87.3% were men. Victims who died included climbers (25.5%), backcountry skiers (22.7%), out-of-bounds skiers (10.0%), snowmobilers (6.8%), in-bounds skiers (5.2%), residents (4.5%), ski patrollers (3.6%), workers (3.6%), and motorists (3.0%). Over the 45-year study period there appear to be decreases in the deaths of in-bounds skiers, highway workers, and motorists. Increasing fatalities were observed among out-of-bounds skiers, snowmobilers, ski patrollers, and backcountry skiers. Most deaths occurred in Colorado (33.0%), Washington (13.2%), and Alaska (12.0%). Conclusions.-Avalanche fatalities have increased over the last 45 years. Climbers, backcountry skiers, out-of-bounds skiers, and more recently snowmobilers constitute the majority of the victims. The decrease in deaths among groups that benefit from avalanche control programs supports the benefit of avalanche prevention strategies. Further study is needed to assess the impact of avalanche safety education for individuals who travel in remote and uncontrolled terrain. Key words: avalanche. trauma, wilderness medicine. skiing
Introduction An avalanche occurs on a slope when the cohesive properties within the snowpack or between the snow and the ground fail to resist downward gravitational forces. Avalanches can occur spontaneously; they may also be triggered by the weight of a person or by explosives. Objects or humans in the path of an avalanche can be swept down the slope. As the avalanche comes to a stop, the snow consolidates rapidly as a result of the release of thermal energy. Previous studies have implicated asphyxia and blunt trauma as the leading causes of deaths in avalanches [1-5]. Although considerable knowledge has been gained in recent years regarding the mechanisms of avalanche activity, little has been published about the victims themselves. This study describes the demographics of avalanche victims in the United States, evaluates trends in the numDirect correspondence to Division of Emergency Medicine; Mailcode #0108; Denver Health Medical Center; Denver, CO 80204 (Dr Page).
ber of persons killed in avalanches over the past 45 years, and describes the type of activities in which victims were engaged at the time of the accident. This represents the largest cohort of avalanche fatalities published to date.
Materials and methods Retrospective data were collected from the national avalanche accident database. Each accident entry in the database documents the number of people who were caught and killed in each avalanche. Additional information available about the victims includes their sex and age, and the time and date in which the accident occurred. We also recorded the duration of burial before retrieval from the snow, the depth in which the head was buried under the snow, and whether the person was fully buried or partially buried. We defined a partially buried victim as a person who had part of his or her body under the snow when the avalanche came to a halt, whereas a
147
Avalanche deaths in the United States Table 1. Description of each activity Activity
Backcountry skier
Climber Guides Helicopter!snowcat Highway workers Hikers Hunters In-bounds skier Miners Miscellaneous Motorist Out-of-bounds skier
Description
Skiing in the backcountry (uncontrolled or remote terrain); skimountaineer. Without skis or snowshoes. On-duty ski or mountain guide. Skiing in uncontrolled or remote terrain. Employees of highway department or operating snowplow. Not using snowshoes or skis. Hunting at the time of the accident. Within a ski area boundary in an area designated as "open". Invoved in a mining operation. Other recreational categories. In a vehicle. Enters a "closed"area or exits the outer boundary of a ski area. Children playing where an avalanche occurs. Paid or volunteer wilderness worker. Rescuing avalanche victims. Caught in a building or town; snow originating on rooftops. On-duty ski patroller. Riding a snowboard. Operating a snowmobile. Using snowshoes. Workers not otherwise specified.
a database in 1960 when the US Forest Service (USFS) Avalanche Program began in Fort Collins, CO. The data prior to 1960 was collected retrospectively from sources, such as ski areas, who were familiar with the accidents. After 1960, database information was reported to and collected by the USFS. Sources of reporting include rescue organizations, emergency medical providers, ski patrollers, law enforcement agencies, reports in the media, and avalanche forecasters. In 1972, the USFS Westwide Avalanche Network computerized the data. The database is currently maintained by one of the authors at the Colorado Avalanche Information Center in Boulder, CO. Colorado population data were collected from annually reported vital statistics published by the Colorado Department of Public Health and Environment [6-8]. Data were analyzed using Pearson correlation tests, and mean values are reported ± standard deviation. Results
Four hundred forty victims died in 324 fatal accidents. The age was known in 252 (57.3%) of the victims. The mean age was 27.6 ± 10.6 years (range, 6-61 years). Rangers The sex of the victims was known in 315 (71.6%) of Rescuers Residents victims: 275 (87.3%) were men and 40 (12.7%) were women. The burial status was known for 319 (72.3%) Ski patroller victims; 87.7% were fully buried, 4.7% were partially Snowboarder buried, and 7.6% were caught but not buried. Duration Snowmobiler of burial before bodies were uncovered was known in Snowshoers 198 (67.3%) of the 319 with a mean of 32.5 ± 115.5 Workers hours (range, 5 minutes to 60 days). Only 29.3% of victims were uncovered in the first hour; 79.3% were uncovered within the first 24 hours. Of the 407 victims fully buried victim was one whose head was buried un- who were partially or fully buried, the depth of burial der the snow. Ratings of victims' avalanche education was known in 211 (51.8%) and was 5.88 ± 5.29 feet. Figure 1 illustrates the increasing number of fatalities was known in 16.1 % and backcountry experience was known in 25.5% of victims. These data were not ana- reported annually (r = 0.64), with the most deaths lyzed. (33.0%) occurring in Colorado (Table 2). An average of The type of preaccident activity is also recorded for 15.0 individuals were killed annually in last 20 years of each accident. Table 1 describes each activity category. the study period, during which 68.2% of the avalanche In some cases, more than one category may describe a deaths in the study period occurred. The number of favictim, but each victim was assigned only one category talities per capita in Colorado has not changed over this for the purposes of analysis. The type of employment 45-year period, as suggested by the correlation of the takes precedence over the type of conveyance used. estimated population of the state of Colorado with the Hunters, ski patrollers, rescuers, climbers, unspecified number of persons killed by avalanches in Colorado (r workers, rangers, and guides are included in their re- = 0.667) (Fig 3). Table 3 lists the numbers of victims spective categories, even if they were using snowmo- killed in each activity category. Deaths in the leading biles, snowboards, or other means of transport. Snow- activity categories for IS-year periods are shown in Fig boarders are not included in the in-bounds and out-of- 2. Trends toward decreasing numbers of deaths are seen bounds categories. among highway workers, motorists, and in-bounds skiThe study population consisted of avalanche fatalities ers. Increasing deaths are seen among out-of-bounds skifrom January 1, 1950, through December 31,1994. The ers, backcountry skiers, and snowmobilers. The month avalanche accident information was first assembled into in which the avalanche occurred was known for all casPlaying
148
Page et al 35
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75
80
85
90
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Fig 1.
The number of fatalities in US avalanches annually (r = 0.643).
es. Although avalanche deaths occurred in each month of the year, 88.0% of fatalities occurred between November and April, with February as the peak month (23.5%). The time in which the fatality occurred was known in 50.7% of victims. Most victims (88.3%) were killed between 0900 and 1600 hours.
ty. Climber deaths initially increased, but then decreased compared with other activities during the last third of the study period. The work of snow scientists, ski patrollers, avalanche forecasters and other avalanche professionals has enhanced the understanding of the physical properties of snow, avalanche dynamics, and improved techniques for
Discussion The number of persons killed in avalanches increased over the 45-year study period. The greatest number of deaths occurred among climbers, backcountry skiers, out-of-bounds skiers, and snowmobilers. Deaths among backcountry skiers, out-of-bounds skiers, and snowmobilers have increased despite advances in avalanche safeTable 2. Victims by state, 1950-1994 State
Colorado Washington Alaska Utah California Idaho Montana Wyoming Nevada Oregon New Hampshire New Mexico New York Maine
Killed
% for period
145 58 53 39 36 27 27 23 9 8 7 3 3 2
33.0 13.2 12.0 8.9 8.2 6.1 6.1 5.2 2.0 1.8 1.6 0.7 0.7 0.5
Table 3. Activities of victims (n = 440). Activity
Killed
% of total
Climber Backcountry skier Out-of-bounds Snowmobiler In-bounds Resident Ski patrol Worker Motorist Highway worker Playing Snowshoer Hiker Rescuer Snowboarder Hunter Miner Helilsnowcat Miscellaneous recreation Guide Ranger Total
112 100 44 30 23 20 16 16 13 12 10 10 9 5 5 4 4 3 2 1 1 440
25.5 22.7 10.0 6.8 5.2 4.5 3.6 3.6 3.0 2.7 2.3 2.3 2.0 1.1 1.1 0.9 0.9 0.7 0.5 0.2 0.2 100.0
149
Avalanche deaths in the United States m1980-94 01965-79 .1950-64
0%
5%
10%
20%
15%
25%
30%
35%
Fatality (% of 15 year total)
Fig 2. Fatalities in leading activity categories expressed as a percentage of 15-year total deaths.
increased, then the death rate among those at risk may have actually decreased. The only previous study of avalanche accidents in the United States is a descriptive study that reports the burial circumstances, diagnoses, and outcomes of 21 avalanche victims in the state of Utah [2]. Twelve fatalities and nine injuries are described during a 6-year study period. European studies have attempted to determine the relationship between burial time (time to extrication) and survival; these studies report that survival decreases with burial time and that the 50% mortality point occurs within approximately 15-35 min [9-12]. The major limitation of these studies is that many persons who are caught and not injured or killed may be unreported. Climbers, backcountry skiers, out-of-bounds skiers, and snowmobilers represent 65% of all avalanche fatal-
avalanche hazard recognition and prediction. Preventive strategies designed to decrease avalanche morbidity now include decisions regarding road closure and active triggering of avalanches with explosives near highways and at developed ski areas. This type of avalanche control prevents the development of unstable layers in the snowpack and results in fewer and less severe avalanches. The marked decrease in fatalities among snowplow drivers, motorists, and in-bounds skiers resulted from these preventive measures. One-third of all avalanche deaths occurred in Colorado. The correlation between the general population of Colorado and avalanche deaths in the state suggests that the per capita rate of avalanche deaths in Colorado may have remained constant. If the percentage of the Colorado population that participates in these activities has 10
•
-
.....
•
-~
~
----------........-~~ ~
~
2.5
3.5
Population (millions)
Fig 3.
Correlation of Colorado population with Colorado avalanche deaths (n
= 111; r = 0.667).
150 ities. The terrain in which climbers are caught may be more prone to avalanches than that traveled by other groups. These four groups may have less training and experience with avalanche prevention and rescue and carry less equipment than avalanche professionals, such as ski patrollers. They may also be far from immediate rescue support, thus increasing extrication time, which has been shown to have a direct effect on survival [9]. Increases in deaths among these groups could reflect an increase in this population, a shift into more avalancheprone terrain, or more risky and less educated practices among these individuals. Climbers, backcountry skiers, and snowmobilers represent some of the groups that venture into remote, uncontrolled, avalanche-prone terrain. It seems intuitive that education in avalanche risk assessment and safety principles would be beneficial for these groups. The ski patrollers who spend a large amount of time exposed to avalanche risk only represent 3.6% of all avalanche deaths. This may be due to the controlled terrain within a ski area, resulting in snowpack that may be more stable and avalanches that may be smaller in depth. Ski patrollers, however, are highly trained in avalanche risk recognition, avoidance of burial, and rescue. They travel in groups, have immediate radio access to additional rescue personnel, and carry avalanche rescue equipment. This provides some indirect evidence that avalanche training imparts some benefits. We believe that this type of education should be available to individuals that venture into avalanche-prone terrain, even though the impact of avalanche training has not been assessed in a controlled fashion. The distinction should be recognized between training in recognition and avoidance of avalanche hazard and training in rescue techniques for victims who have been caught. Reliance on rescue education with ignorance of prevention education may actually increase one's morbidity and mortality from an avalanche by providing a false sense that one can easily and safely survive an avalanche if proper rescue techniques are used. The retrospective nature of the analysis is a limitation of this work. Some elements of the database were incomplete or were collected in a nonstandardized manner. Information such as weather data, composition of the snowpack, safety equipment carried, access to rescue resources, and communication capabilities were not available. Ratings of skill in snow activity and avalanche safety training were available for a limited number of victims but may be more available for future accidents. Information on individuals involved in avalanches and not reported prevents us from making accurate conclusions regarding trends in overall mortality of avalanche accidents. We suspect that factors that prevent accidents
Page et al from being reported are remoteness, lack of morbidity and mortality, absence of rescue group or law enforcement involvement, lack of knowledge of how to report accidents, and the desire that others not know about the accident.
Conclusion Avalanche fatalities have increased over the last 45 years. Climbers, backcountry skiers, out-of-bounds skiers, and more recently snowmobilers constitute the majority of the victims. The decrease in deaths among groups that benefit from avalanche control programs supports the benefit of prevention strategies. Our data suggest that the best way to prevent avalanche mortality is primary prevention. Deaths have decreased among inbounds skiers, highway workers, and motorists. These groups are the recipients of preventative strategies emerging from a growing understanding of snow science and its applications. Further study is needed to assess the impact of avalanche safety education for individuals who travel in remote and uncontrolled terrain.
Acknowledgments Some of the data in this manuscript were previously reported as posters at the Rocky Mountain Conference on Emergency Medicine in Vail, CO, January 1997, and at the Rocky Mountain Conference on Emergency Medicine in Steamboat Springs, CO, January 1998.
References 1. Brugger H, Durrer B, Adler-Kastner L. On-site triage of avalanche victims with asystole by the emergency doctor. Resuscitation. 1996;31:11-16. 2. Grossman MD, Saffle JR, Thomas F, Tremper B. Avalanche trauma. J Trauma. 1989;29:1705-1709. 3. Mair P, Kornberger E, Furtwaengler W, Balogh D, Antretter H. Prognostic markers in patients with severe accidental hypothermia and cardiocirculatory arrest. Resuscitation. 1994;27:47-54. 4. Stalsberg H, Albretsen C, Gilbert M, Kearney M, Moestue E, Nordrum I, Morten AO. Mechanisms of death in avalanche victims. Virchows Arch Pathol Anat Histopathol. 1989;414:415-422. 5. Tough SC, Butt JC. A review of 19 fatal injuries associated with backcountry skiing. Am J Forensic Med Pathol. 1993;14:17-21. 6. Colorado Department of Health and Environment, Health Statistics and Vital Records Division. Colorado Vital Statistics 1995.
Avalanche deaths in the United States 7. Colorado Department of Health, Health Statistics Section. Colorado Vital Statistics. Denver, CO: Colorado Department of Health; 1985. 8. Colorado State Department of Health, Records and Statistics Section. Annual Report of Vital Statistics. Denver, CO: Colorado State Department of Health; 1961. 9. Falk M, Brugger H, Adler-Kastner L. Avalanche survival chances. Nature. 1994;368:21. 10. Brugger, H, Falk M, Buser 0, Tschirky, EE L'arva: bilan
151 et perspectives [in French]. Neige et Avalanches. 1997;78: 8-11. 11. Brugger, H, Falk M, Adler-Kastner L. Der lawinennotfall neue aspetke zur pathophysiologie und therapie von lawinenverschiitteten [in German]. Middle Eur J Med. 1997; 109:145-159. 12. Burtscher M. Avalanche survival chances. Nature. 1994; 371:482.
ORIGINAL RESEARCH
Avalanche deaths in the United States: a 45-year analysis CHARLES E. PAGE, MD; DALE ATKINS, BA; LEE W. SHOCKLEY, MD; MICHAEL YARON, MD From the Denver Health Medical Center, Division Qf Emergency Medicine (Dr Page and Dr Shockley). Ihe Colorado Avalanche Information Center, Colorado Geologic Survey (Mr AIkins). and the University of Colorado Health Sciences Center, Division of Emergency Medicine, Colorado Emergency Medicine Research Cemer (Dr Yaron).
Objective.-To describe the demographic characteristics and patterns of death of persons killed in snow avalanches over a 45-year study period. Methods.-The national avalanche database was the source of data in this retrospective, descriptive study. Results.-A total of 440 victims were killed in 324 fatal avalanches, of which 87.7% were fully buried, 4.7% were partially buried, and 7.6% were not buried. The average age was 27.6 :!: 10.6 years, and 87.3% were men. Victims who died included climbers (25.5%), backcountry skiers (22.7%), out-of-bounds skiers (10.0%), snowmobilers (6.8%), in-bounds skiers (5.2%), residents (4.5%), ski patrollers (3.6%), workers (3.6%), and motorists (3.0%). Over the 45-year study period there appear to be decreases in the deaths of in-bounds skiers, highway workers, and motorists. Increasing fatalities were observed among out-of-bounds skiers, snowmobilers, ski patrollers, and backcountry skiers. Most deaths occurred in Colorado (33.0%), Washington (13.2%), and Alaska (12.0%). Conclusions.-Avalanche fatalities have increased over the last 45 years. Climbers, backcountry skiers, out-of-bounds skiers, and more recently snowmobilers constitute the majority of the victims. The decrease in deaths among groups that benefit from avalanche control programs supports the benefit of avalanche prevention strategies. Further study is needed to assess the impact of avalanche safety education for individuals who travel in remote and uncontrolled terrain. Key words: avalanche. trauma, wilderness medicine. skiing
Introduction An avalanche occurs on a slope when the cohesive properties within the snowpack or between the snow and the ground fail to resist downward gravitational forces. Avalanches can occur spontaneously; they may also be triggered by the weight of a person or by explosives. Objects or humans in the path of an avalanche can be swept down the slope. As the avalanche comes to a stop, the snow consolidates rapidly as a result of the release of thermal energy. Previous studies have implicated asphyxia and blunt trauma as the leading causes of deaths in avalanches [1-5]. Although considerable knowledge has been gained in recent years regarding the mechanisms of avalanche activity, little has been published about the victims themselves. This study describes the demographics of avalanche victims in the United States, evaluates trends in the numDirect correspondence to Division of Emergency Medicine; Mailcode #0108; Denver Health Medical Center; Denver, CO 80204 (Dr Page).
ber of persons killed in avalanches over the past 45 years, and describes the type of activities in which victims were engaged at the time of the accident. This represents the largest cohort of avalanche fatalities published to date.
Materials and methods Retrospective data were collected from the national avalanche accident database. Each accident entry in the database documents the number of people who were caught and killed in each avalanche. Additional information available about the victims includes their sex and age, and the time and date in which the accident occurred. We also recorded the duration of burial before retrieval from the snow, the depth in which the head was buried under the snow, and whether the person was fully buried or partially buried. We defined a partially buried victim as a person who had part of his or her body under the snow when the avalanche came to a halt, whereas a
147
Avalanche deaths in the United States Table 1. Description of each activity Activity
Backcountry skier
Climber Guides Helicopter!snowcat Highway workers Hikers Hunters In-bounds skier Miners Miscellaneous Motorist Out-of-bounds skier
Description
Skiing in the backcountry (uncontrolled or remote terrain); skimountaineer. Without skis or snowshoes. On-duty ski or mountain guide. Skiing in uncontrolled or remote terrain. Employees of highway department or operating snowplow. Not using snowshoes or skis. Hunting at the time of the accident. Within a ski area boundary in an area designated as "open". Invoved in a mining operation. Other recreational categories. In a vehicle. Enters a "closed"area or exits the outer boundary of a ski area. Children playing where an avalanche occurs. Paid or volunteer wilderness worker. Rescuing avalanche victims. Caught in a building or town; snow originating on rooftops. On-duty ski patroller. Riding a snowboard. Operating a snowmobile. Using snowshoes. Workers not otherwise specified.
a database in 1960 when the US Forest Service (USFS) Avalanche Program began in Fort Collins, CO. The data prior to 1960 was collected retrospectively from sources, such as ski areas, who were familiar with the accidents. After 1960, database information was reported to and collected by the USFS. Sources of reporting include rescue organizations, emergency medical providers, ski patrollers, law enforcement agencies, reports in the media, and avalanche forecasters. In 1972, the USFS Westwide Avalanche Network computerized the data. The database is currently maintained by one of the authors at the Colorado Avalanche Information Center in Boulder, CO. Colorado population data were collected from annually reported vital statistics published by the Colorado Department of Public Health and Environment [6-8]. Data were analyzed using Pearson correlation tests, and mean values are reported ± standard deviation. Results
Four hundred forty victims died in 324 fatal accidents. The age was known in 252 (57.3%) of the victims. The mean age was 27.6 ± 10.6 years (range, 6-61 years). Rangers The sex of the victims was known in 315 (71.6%) of Rescuers Residents victims: 275 (87.3%) were men and 40 (12.7%) were women. The burial status was known for 319 (72.3%) Ski patroller victims; 87.7% were fully buried, 4.7% were partially Snowboarder buried, and 7.6% were caught but not buried. Duration Snowmobiler of burial before bodies were uncovered was known in Snowshoers 198 (67.3%) of the 319 with a mean of 32.5 ± 115.5 Workers hours (range, 5 minutes to 60 days). Only 29.3% of victims were uncovered in the first hour; 79.3% were uncovered within the first 24 hours. Of the 407 victims fully buried victim was one whose head was buried un- who were partially or fully buried, the depth of burial der the snow. Ratings of victims' avalanche education was known in 211 (51.8%) and was 5.88 ± 5.29 feet. Figure 1 illustrates the increasing number of fatalities was known in 16.1 % and backcountry experience was known in 25.5% of victims. These data were not ana- reported annually (r = 0.64), with the most deaths lyzed. (33.0%) occurring in Colorado (Table 2). An average of The type of preaccident activity is also recorded for 15.0 individuals were killed annually in last 20 years of each accident. Table 1 describes each activity category. the study period, during which 68.2% of the avalanche In some cases, more than one category may describe a deaths in the study period occurred. The number of favictim, but each victim was assigned only one category talities per capita in Colorado has not changed over this for the purposes of analysis. The type of employment 45-year period, as suggested by the correlation of the takes precedence over the type of conveyance used. estimated population of the state of Colorado with the Hunters, ski patrollers, rescuers, climbers, unspecified number of persons killed by avalanches in Colorado (r workers, rangers, and guides are included in their re- = 0.667) (Fig 3). Table 3 lists the numbers of victims spective categories, even if they were using snowmo- killed in each activity category. Deaths in the leading biles, snowboards, or other means of transport. Snow- activity categories for IS-year periods are shown in Fig boarders are not included in the in-bounds and out-of- 2. Trends toward decreasing numbers of deaths are seen bounds categories. among highway workers, motorists, and in-bounds skiThe study population consisted of avalanche fatalities ers. Increasing deaths are seen among out-of-bounds skifrom January 1, 1950, through December 31,1994. The ers, backcountry skiers, and snowmobilers. The month avalanche accident information was first assembled into in which the avalanche occurred was known for all casPlaying
148
Page et al 35
• 30
1
25
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55
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•
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i
• ! I
!
••
•
• 65
70
75
80
85
90
Year
Fig 1.
The number of fatalities in US avalanches annually (r = 0.643).
es. Although avalanche deaths occurred in each month of the year, 88.0% of fatalities occurred between November and April, with February as the peak month (23.5%). The time in which the fatality occurred was known in 50.7% of victims. Most victims (88.3%) were killed between 0900 and 1600 hours.
ty. Climber deaths initially increased, but then decreased compared with other activities during the last third of the study period. The work of snow scientists, ski patrollers, avalanche forecasters and other avalanche professionals has enhanced the understanding of the physical properties of snow, avalanche dynamics, and improved techniques for
Discussion The number of persons killed in avalanches increased over the 45-year study period. The greatest number of deaths occurred among climbers, backcountry skiers, out-of-bounds skiers, and snowmobilers. Deaths among backcountry skiers, out-of-bounds skiers, and snowmobilers have increased despite advances in avalanche safeTable 2. Victims by state, 1950-1994 State
Colorado Washington Alaska Utah California Idaho Montana Wyoming Nevada Oregon New Hampshire New Mexico New York Maine
Killed
% for period
145 58 53 39 36 27 27 23 9 8 7 3 3 2
33.0 13.2 12.0 8.9 8.2 6.1 6.1 5.2 2.0 1.8 1.6 0.7 0.7 0.5
Table 3. Activities of victims (n = 440). Activity
Killed
% of total
Climber Backcountry skier Out-of-bounds Snowmobiler In-bounds Resident Ski patrol Worker Motorist Highway worker Playing Snowshoer Hiker Rescuer Snowboarder Hunter Miner Helilsnowcat Miscellaneous recreation Guide Ranger Total
112 100 44 30 23 20 16 16 13 12 10 10 9 5 5 4 4 3 2 1 1 440
25.5 22.7 10.0 6.8 5.2 4.5 3.6 3.6 3.0 2.7 2.3 2.3 2.0 1.1 1.1 0.9 0.9 0.7 0.5 0.2 0.2 100.0
149
Avalanche deaths in the United States m1980-94 01965-79 .1950-64
0%
5%
10%
20%
15%
25%
30%
35%
Fatality (% of 15 year total)
Fig 2. Fatalities in leading activity categories expressed as a percentage of 15-year total deaths.
increased, then the death rate among those at risk may have actually decreased. The only previous study of avalanche accidents in the United States is a descriptive study that reports the burial circumstances, diagnoses, and outcomes of 21 avalanche victims in the state of Utah [2]. Twelve fatalities and nine injuries are described during a 6-year study period. European studies have attempted to determine the relationship between burial time (time to extrication) and survival; these studies report that survival decreases with burial time and that the 50% mortality point occurs within approximately 15-35 min [9-12]. The major limitation of these studies is that many persons who are caught and not injured or killed may be unreported. Climbers, backcountry skiers, out-of-bounds skiers, and snowmobilers represent 65% of all avalanche fatal-
avalanche hazard recognition and prediction. Preventive strategies designed to decrease avalanche morbidity now include decisions regarding road closure and active triggering of avalanches with explosives near highways and at developed ski areas. This type of avalanche control prevents the development of unstable layers in the snowpack and results in fewer and less severe avalanches. The marked decrease in fatalities among snowplow drivers, motorists, and in-bounds skiers resulted from these preventive measures. One-third of all avalanche deaths occurred in Colorado. The correlation between the general population of Colorado and avalanche deaths in the state suggests that the per capita rate of avalanche deaths in Colorado may have remained constant. If the percentage of the Colorado population that participates in these activities has 10
•
-
.....
•
-~
~
----------........-~~ ~
~
2.5
3.5
Population (millions)
Fig 3.
Correlation of Colorado population with Colorado avalanche deaths (n
= 111; r = 0.667).
150 ities. The terrain in which climbers are caught may be more prone to avalanches than that traveled by other groups. These four groups may have less training and experience with avalanche prevention and rescue and carry less equipment than avalanche professionals, such as ski patrollers. They may also be far from immediate rescue support, thus increasing extrication time, which has been shown to have a direct effect on survival [9]. Increases in deaths among these groups could reflect an increase in this population, a shift into more avalancheprone terrain, or more risky and less educated practices among these individuals. Climbers, backcountry skiers, and snowmobilers represent some of the groups that venture into remote, uncontrolled, avalanche-prone terrain. It seems intuitive that education in avalanche risk assessment and safety principles would be beneficial for these groups. The ski patrollers who spend a large amount of time exposed to avalanche risk only represent 3.6% of all avalanche deaths. This may be due to the controlled terrain within a ski area, resulting in snowpack that may be more stable and avalanches that may be smaller in depth. Ski patrollers, however, are highly trained in avalanche risk recognition, avoidance of burial, and rescue. They travel in groups, have immediate radio access to additional rescue personnel, and carry avalanche rescue equipment. This provides some indirect evidence that avalanche training imparts some benefits. We believe that this type of education should be available to individuals that venture into avalanche-prone terrain, even though the impact of avalanche training has not been assessed in a controlled fashion. The distinction should be recognized between training in recognition and avoidance of avalanche hazard and training in rescue techniques for victims who have been caught. Reliance on rescue education with ignorance of prevention education may actually increase one's morbidity and mortality from an avalanche by providing a false sense that one can easily and safely survive an avalanche if proper rescue techniques are used. The retrospective nature of the analysis is a limitation of this work. Some elements of the database were incomplete or were collected in a nonstandardized manner. Information such as weather data, composition of the snowpack, safety equipment carried, access to rescue resources, and communication capabilities were not available. Ratings of skill in snow activity and avalanche safety training were available for a limited number of victims but may be more available for future accidents. Information on individuals involved in avalanches and not reported prevents us from making accurate conclusions regarding trends in overall mortality of avalanche accidents. We suspect that factors that prevent accidents
Page et al from being reported are remoteness, lack of morbidity and mortality, absence of rescue group or law enforcement involvement, lack of knowledge of how to report accidents, and the desire that others not know about the accident.
Conclusion Avalanche fatalities have increased over the last 45 years. Climbers, backcountry skiers, out-of-bounds skiers, and more recently snowmobilers constitute the majority of the victims. The decrease in deaths among groups that benefit from avalanche control programs supports the benefit of prevention strategies. Our data suggest that the best way to prevent avalanche mortality is primary prevention. Deaths have decreased among inbounds skiers, highway workers, and motorists. These groups are the recipients of preventative strategies emerging from a growing understanding of snow science and its applications. Further study is needed to assess the impact of avalanche safety education for individuals who travel in remote and uncontrolled terrain.
Acknowledgments Some of the data in this manuscript were previously reported as posters at the Rocky Mountain Conference on Emergency Medicine in Vail, CO, January 1997, and at the Rocky Mountain Conference on Emergency Medicine in Steamboat Springs, CO, January 1998.
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