Avalanche Incidents in New Zealand
An in-depth look at 20 years of avalanche incident data
New Zealand is a land of diverse and dramatic landscapes. From the rugged coastline to the highest mountain peaks and all the variety in between, there is no place on Earth quite like Aotearoa.
Spoilt for adventure opportunities that rival the world's best, it is no surprise that New Zealand's mountains are a hotspot for alpine recreation. Whether it is tramping, hunting, mountaineering, or ski touring, there's something for everyone. However, incidents occur when dealing with the challenges this environment poses.
The New Zealand Mountain Safety Council (MSC) leads the country’s land-based outdoor recreation prevention work and runs the New Zealand Avalanche Advisory (NZAA) as its primary alpine safety prevention tool. MSC has conducted an in-depth analysis of 20 years' worth of avalanche incident data in order to paint a ‘bigger picture’ perspective of the incidents in New Zealand.
This analysis of avalanche incidents was undertaken with the goal of raising awareness of avalanche danger and encouraging critical thinking both in planning and when out in the field.
This story presents some of these key findings.
The data MSC uses comes from a range of sources. Most of it is sourced through partnerships with government agencies and complemented by additional data from sector tools and public observations.
Accident Compensation Corporation (ACC) provides a comprehensive dataset for all incidents that involve someone sustaining an injury and requiring medical attention.
The NZ Police and Rescue Coordination Centre NZ represent New Zealand's two Search and Rescue (SAR) Coordinating Authorities. If you are involved in an incident and SAR assistance is required, one of these two authorities will lead the rescue operation.
In New Zealand, the professional mountain community, including ski areas, heli-ski operators and guiding companies use a common platform to record and share weather, snowpack and avalanche data, known as the 'InfoEx'.
Finally, in the most tragic of situations, the New Zealand Coronial Services Unit provides comprehensive fatalities data.
In 2018, MSC launched a public observation reporting tool as part of the New Zealand Avalanche Advisory. This type of information is not available for the time period of this data analysis (1999-2018), but incidents reported via this tool will be included in future updates to this story.
From 1999 to 2018, there were 742 reported avalanche incidents, including 27 fatalities.
This equates to just over 37 reported incidents per year, and an average of 1.35 fatalities.
For clarity, in this analysis, an avalanche 'incident' is classified as one where a person unintentionally triggered the avalanche or at least one person was caught. Witnessed avalanches in which no one was caught have not been included in this data, nor have we included avalanches intentionally caused during control work.
The data captured as part of these incidents is in most cases extensive, and the list of findings is comprehensive. Through this story, we will share key findings in two parts.
Part One will focus on all avalanche incidents:
- Time series; by year, month and time of day
- Triggers by activity type
- Incidents by elevation, aspect, slope incline, size, time of day
- Incidents by New Zealand Avalanche Advisory danger ratings
- Demographics
Part Two will focus on avalanche fatalities:
- Activity at the time of the event
- Locations of fatal avalanches
- Cause of death
- Group status at the time of the event
Part One
Scroll down to navigate through the relevant findings. Please note that on a mobile device the frames below are not interactive.
Fig 1. Incidents and Fatalities per Calendar Year
Note: 2011 does not have complete data for avalanche incidents due to file management changeover, however the zero fatalities statistic is accurate.
Fig 2. Activity Trigger Types
Skiers and Snowboarders make up the vast majority of reported avalanche incidents. However, there may be some reporting bias here as skiers and snowboarders often report said incidents to patrol staff at a nearby ski field, allowing for the incident to be captured by InfoEx. Climbers and trampers don't usually access the backcountry via ski fields and thus don't report in this fashion. But with the development of the NZAA Public Observations tool in 2018 (find it at avalanche.net.nz ), now anyone can independently report an avalanche incident for any activity type. (Note: A remote event is defined as one occurring at some distance (typically > 5 m) from the probable trigger. The snow at the trigger point does not move.)
Fig 3. Incidents by Elevation
Figure 2 indicated that the primary activity reporting avalanche incidents has been backcountry skiers and snowboarders. Much of backcountry skiing and snowboarding activity occurs in the 1500-2000m elevation band, nearby or in between ski-areas located at these elevations. So it's possible this data may be more reflective of participation.
Fig 4. Incidents by Aspect
(Note: Percentages don't add up to 100% as there is overlap. For example, SW aspect is counted for Southerly aspects as well as Westerly aspects. The figures should be interpreted as the percentage of incidents occurring in the aspect range shown) The most likely aspect to have an incident has been E/SE aspects, which makes sense within New Zealand's geographical and meteorological context. These aspects are more likely to be wind-loaded by our predominant winds, and weaknesses in the snowpack are more likely to persist on southerly aspects. It's also where the better snow for skiing/snowboarding often is; no surprise that's where the activity is too.
Fig 5. Incidents by Slope Incline
This data follows what is seen internationally and what is taught in avalanche courses. The slope angle range from 30-45 degrees is where avalanches are most likely to occur. However, there are still a reasonable number of avalanche incidents that occurred outside of this range.
Fig 6. Incidents by Size
The vast majority of avalanche incidents have been size 1-2 avalanches. The data on avalanche type is unfortunately not very specific. However, the vast majority of reported avalanche incidents (around 85%) have been some form of slab avalanche. Loose avalanches make up around 10%, and the rest are unknown. As a reminder, these are only reported avalanches that were unintentionally triggered or where people have been caught; this is not a reflection of all observed avalanche activity.
Fig 7. Incidents by Time of Day Observed
This time plot of when in the day avalanche incidents have occurred follows what we would expect. As the temperature warms up and the sun plays more of an influence on the snowpack, some types of avalanches are more likely to occur, hence the increase in incidents in the afternoon. When accounting for different activity types, all activities peaked in the 11:00-13:00 timeframe. However, Mountaineering and Backcountry Snowboarding incident numbers rapidly reduced in the afternoon following this peak. Backcountry Skiing and Heli-skiing had a slower taper-off, similar to the overall picture that is seen above.
Fig 8. Incidents by NZAA Danger Rating
There are a couple of takeaways from this figure. 1) There are very few incidents at High or Extreme danger ratings, it's great to see most are following advice to avoid avalanche terrain during these times. 2) 15% of avalanche incidents are occurring during 'Low' avalanche danger. A reminder that 'low avalanche danger does not mean no avalanche danger'.
Fig 9. Gender of People Involved in Incidents
This data follows what is seen internationally. Men are far more likely to be involved in an avalanche incident, even when accounting for participation differences.
Fig 10. Age of People Involved in Incidents
There is enough 'unknown' here to warrant caution in drawing strong conclusions. However, this data appears to be similar to what is seen internationally.
Part Two
Continue scrolling to see more findings relating specifically to the 27 avalanche fatalities.
Of the 27 fatalities since 1998, 19 have involved mountaineers. This represents 70% of all fatalities. This statistic is unusual internationally, elsewhere mountaineers make up a far smaller proportion of fatalities.
Three fatalities have involved heliskiers.
Two fatalities have involved trampers.
Backcountry skiing and snowboarding have each had one fatality, and there's also one incident where the activity at the time is not known.
The interactive map below indicates the approximate location of avalanche fatalities. You can zoom in, and hovering over the pin (on a desktop) will reveal the month and date of each tragedy.
Locations of avalanche fatalities (*approximate). Key located bottom left.
Fig 11. Immediate Cause of Death
Once again, there is enough 'unknown' here to warrant caution in making any strong conclusions. Though it appears there is a roughly even split between trauma and asphyxiation/suffocation as the immediate cause of death.
Fig 12. Group Status at the Time of the Avalanche
The vast majority of avalanche fatalities have been travelling in a group rather than solo.
Conclusion
Avalanches are an ever-present danger in the alpine regions of the New Zealand backcountry. Each year thousands of people participate in backcountry snow sports activities across New Zealand, either consciously or unconsciously exposing themselves to the danger of avalanches.
Thankfully, New Zealand does not experience the same amount of avalanche fatalities as other developed nations. However, when accounting for our small population our numbers are relatively similar. The potential for tragedy is always present, and a continued reduction in avalanche incidents is always desired.
These insights have been presented for public use in an effort to raise awareness of avalanche danger and encourage critical thinking both in planning and when in the field. MSC will update this analysis as new data becomes available.
Staying safe in avalanche terrain
Use the following resources to learn more about avalanche safety:
