Crystal Ball Volume 23 - Spring 2013

nEW ZEALAnD MOunTAIn SAFETY COunCIL

vOLUME 23 SPRING 2013

PHOTO: PETER BILOUS

pERIODICAL OF ThE nEW ZEALAnD AVALAnChE COMMunITY

www.avalanche.net.nz www.mountainsafety.org.nz www.adventuresmart.org.nz www.incidentreport.org.nz CRYSTAL CRYSTAL BALL BALL | | Periodical of the New Zealand Avalanche Community

DISCOVER MORE, SAFELY 1

CONTENTS 01 Welcome 02

Bittersweet winter

02

Snow and Avalanche Committee (SAC)

03

SAC - 2013 Accident Summary

04

SAC updates - Rescue

05

SAC updates - Education

07

Research - Shear strength probe

08

Research - Rock striations

10

INFOEX use at the Remarkables

12

New BAA danger signs

13

Avalanche.net.nz website

15

Regional forecaster summaries

30 Case Study - Cracking and persistent deep slab 33 Case Study - Destructive June avalanche cycle in Canterbury

The Crystal Ball Volume 23, Spring 2013 Editor: Gordie Smith Managing Editor: Andrea Corrigan Designer: Gordie Smith Cover Photo Credit: Peter Bilous - 2013 stage 2 graduate Marcus Malden in the pit. Nowhere to go but up!

Thank you to the contributors for giving permission to reproduce their material.

Copyright © New Zealand Mountain Safety Council 2013.

All rights reserved.

All opinions expressed in this magazine are not necessarily those of the New Zealand Mountain Safety Council. While efforts are made to check facts are accurate, responsibility lies with the author.

Editorial and Advertising enquiries Do you have something to say or show? We would like articles relating to the professional avalanche industry, public avalanche safety, teaching tips, research papers, accounts of avalanche events, book and gear reviews, event listings, interviews, letters to the editor, and humorous stories related to avalanches.

We are also looking for winter mountain photography of avalanches, touring, terrain, skiing, snowboarding, active control work, backcountry recreation or avalanche awareness activities.

For more information please contact: Andrew Hobman Tel: +64 27 446 2626 Fax: +64 4 385 7366 Email: andrew.hobman@mountainsafety.org.nz To have your voice heard at the SAC committee, contact your industry representative, or email: manager@avalanche.net.nz

WELCOME Hi and welcome to the spring edition of the 2013 Crystal Ball. It has, as always, been a busy winter working on the education programmes and public outreach events, the Backcountry Avalanche Advisories, the Info-Ex and trying to get our heads in the snow.

As I began to write this I read over the introduction to the 2012 spring edition and I could have cut and pasted it word for word. In 2012 we had a winter punctuated by early snow, torrential rain, fluctuating freezing levels, gale force winds and finally late snow to low levels as I wrote. 2013 is beginning to look like a trending pattern of how our winters will be in the future with extreme weather events becoming the norm and the snow-sport industry surviving on a couple of large snow falls.

Of course these large weather events can bring record amounts of snow and avalanche cycles that this year caused a fair amount of damage to lifts, buildings and farm fences.

They also reminded us of the potential for avalanches to run in places that we’ve rarely seen or well beyond historic maximum run-outs. As Bruce Tremper told us at the 2011 Southern Hemisphere Avalanche Conference “beware the Black Swan event, always expect the unexpected” It was pleasing to see that the farming sector were buying transceivers, shovels and probes for their workers to wear while recovering sheep after the big June snowfall in Canterbury. Although it is rare, we have had avalanche fatalities while people have been rescuing stranded livestock.

Unfortunately we did have a fatality caused by an avalanche this year. Although the mass of snow was very small the consequences of being swept of their feet at that spot were fatal. We have been very lucky that there have been no fatalities for a number of years, although the near misses have been significant. The statistics for climbers dying in avalanches in New Zealand are not great with over half of all deaths involving climbers. We are working with this sector to try and increase their awareness and skill level so that this trend does not continue.

For those of you heading into the hills this spring and summer please spread the word and your knowledge to others. Knowing how to identify and avoid avalanches should be as fundamental as how to tie a figure of eight knot.

As always, we welcome your feedback and any suggestions on the content. If you have any personal stories or articles, we would love to see them so please contact us with your submissions and please ensure that this gets printed off and left around the office for all to read.

See you out in the hills.

- Andrew ‘Hobbie’ Hobman, Avalanche and Alpine programme manager

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Convenor’s corner

// bittersweet winter

Hello spring and farewell winter, While the spring winds may somewhat strip us of our ability to enjoy the receding snowline, we at least have a moment to reflect on the season and what the future may have in store.

This winter may well be remembered as the one that started with a big bang and fizzled to the warmest midwinter in living memory. It was followed by some fine early September quality conditions before tapering to average spring mush.

Highlights include 50 participants earning their Stage 1 Avalanche Safety Certificate through Otago, Tai Poutini and Whiteria Polytechnics. This year also marks the highest number of Stage 2 graduates (15) in one year. The Avalanche Education Working Group (AEWG) managed to advise and consult with industry and Skills Active to help put forth a slightly revised structure of avalanche education for the New Zealand Qualifications Authority (NZQA) framework as part of the Targeted Review of Qualifications (TRoQ) process. Stage 1 has begun some online pre-course study to help better prepare those attending and make time for more practical and active learning opportunities when on course. Stage 2 also saw improvements by lowering entry requirements to the Field Training and providing clear benchmarks prior to the Integrated Practical Assessment.

It was great to see these improvements being made as a direct result of the feedback received from previous students and the industry organisations they belong to; your voice matters.

On the down side, we experienced the loss of some very talented and special members of the NZ mountain community. Both spectrums of the avalanche phenomena made themselves apparent from the relatively large event that took Marty and Denali Schmidt from their camp on K2 to the pocket size slab with a severe fall consequence that claimed Jamie Vinton-Boot behind the Remarkables.

Let’s hope we can return to a period of no fatalities as we managed in the 3 years prior.

Looking ahead, we can expect the MBIE and the adventure activities review process to have an increasing impact on us; personally, organisationally and industry wide. Expect tighter expectations and controls as to who does what and where they do it. Also expect fewer educational providers as those that only offer a few courses a year, have difficulty justifying the increased audit related operating costs. You can look forward to those that are still out there, to have good robust safety management systems and hopefully fewer accidents as well; a welcome outcome.

In summer parting, I hope you make the time to reflect on your own practices, learn from others and put in place a plan to improve the way you do things. Take care and enjoy the summer.

–Peter Bilous Snow and Avalanche Committee Convenor

Above: Lydia Brady coordinates a simluated rescue excercise on this years Stage 2 Field Training course. Other students perform a probe line in the backcground

Snow and Avalanche Committee (SAC) The mission of MSC’s Snow and Avalanche Committee: To provide expert advice and support to the council on appropriate strategies to foster public safety in snow environments including: • Overseeing the training, assessments and qualifications of instructors to ensure that national standards are maintained and enhanced • Overseeing the professional training programmes of all providers as required • Monitoring, research and review trends in snow and avalanche activities to ensure the Council remains the leading authority for safety in this environment.

Convenor: Peter Bilous (Otago Polytech & AEWG rep) Members: Dr I Owens (University of Canterbury) Don Bogie (Department of Conservation) Arthur Tyndall & Nick Jarmin (Club Ski Fields) Wayne Carran (Downer EDI Works) Andy Hoyle (SAANZ North Island) John Hooker (SAANZ South Island) Pete Zimmer (LandSAR) Kevin Boekholt (NZMGA) Andrew Hobman & Gordon Smith (NZMSC)

To have your voice heard at the SAC committee, contact your industry representative or email manager@avalanche.net.nz

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Sac - Accident/incident summary

-2013

// gordie smith

Assistant Avalanche programme manager New Zealand Mountain Safety Council

During the last decade, statistics gathered from data collected by the New Zealand Mountain Safety Council, show that during an average year in New Zealand there will be 37 reported avalanche involvements, resulting in 23.6 people being caught, 1.25 of whom will die.

To date, in the 2013 calendar year, there were 24 reported avalanche incidents and accident events involving people and/or property. 19 events involved people, 13 of whom managed to escape off the moving debris, 6 were partially buried non critically, and none were critically buried (impaired airway) either partially or fully. There was one fatality due to trauma rather than burial, and one other event produced minor injuries to lower extremities.

14 skiers made up the majority of those that were caught, along with four snowboarders, and one climber (fatality). While we lack detail on a few of the events, all known reported involvements were males aged between 26 and 44yrs.

Two naturally triggered events and two explosive triggered events damaged structures - ski area plant and machinery.

Of the 24 reported events 6 took place in the North Island. The first reported events were logged June 20th, and the last on September 19th.

2013 Involvement statistics according to activity: Climbing Ski Patrol Ski/Board Control Work in Ski Area Number of events Part or full burials Fatalities

Backcountry Ski

Backcountry Heli Ski / Board Board

In Vehicles Total

1

5

0

6

2

5

0

19

1

3

0

1

0

1

0

6

1

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SAC - updates // editor avalanche rescue - Smart phones Apps, are they a realistic alternative to a transceiver?

The Snow and Avalanche Committee (SAC) of the NZMSC recommend the following warning message:

“Smart phones should not be used as an alternative to avalanche transceivers. Avalanche transceivers need to conform and use the international standard frequency of 457kHz.” -SAC meeting 18 October 2013

Currently there are three smart phone ‘Apps’ that are on the market which call themselves a type of ‘missing person tracker’, and advertise they can be used in an avalanche search scenario.

App Name

Web address:

iPhone

Android

iSis Snøg Snowhere

http://www.isis-application.com/en/ http://www.avalanchebuddy.com/ http://charcoalfrost.com/

Yes No Yes

Yes Yes No

While software developers are advancing forward quickly with innovative uses for smart phones, the hardware technologies that they make use of, namely Cell Networks, WIFI, GPS, and Bluetooth, have limitations in both range, accuracy, and most importantly, are not compatible with the current international standard of 457kHz for avalanche transceivers.

There is a lack of verifiable testing on any of these apps. Even the ‘App’ developers point out (some more boldly than others), that these smart phone apps are not an alternative to an avalanche transceiver.

Recently (Oct 24, 2013), the Canadian Avalanche Centre (CAC) issued a press release which also reinforces this warning for backcountry users. Dr James Floyer (PhD), a senior forecaster for the CAC has written a discussion paper, which explains these concerns in greater depth.

Click here to read the CAC press release Click here to read Dr Floyer’s Discussion paper

avalanche rescue - New technologies in development NASA and the U.S. Department of Homeland Security are collaborating on a first-of-its-kind portable radar device to detect the heartbeats and breathing patterns of victims trapped in large piles of rubble resulting from a disaster.

The prototype technology, called ‘Finding Individuals for Disaster and Emergency Response’ (FINDER) can locate individuals buried as deep as about 9 m in crushed materials, hidden behind about 6 m of solid concrete, and from a distance of about 30 m in open spaces.

The technology works by beaming microwave radar signals into the piles of debris and analyzing the patterns of signals that bounce back. Earthquakes and tornadoes produce twisted and shattered wreckage, such that any radar signals bouncing back from these piles are tangled and hard to decipher. NASA’s expertise in data processing helped with this challenge. Advanced algorithms isolate the tiny signals from a person’s moving chest by filtering out other signals.

FINDER is currently being tested by the Federal Emergency Management Agency.

Click here to see a short YouTube video

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Sac - updates // editor Education The introduction this winter of a free online avalanche theory course proved very popular. Approximately 1000 people went through all the pages of this online resource which is available here - ONLINE AVALANCHE COURSE A self marking quiz was also developed to test people’s understanding and help reinforce learning points. This was taken by 360 people during the winter. Those enrolled for the recreation level courses of Avalanche Awareness (AA is 1.5 days), and Backcountry (BC is 4 days) were given this online resource and quiz as ‘pre-course’ learning. Anecdotal evidence from course instructors show that overall, students came to courses with a more similar base level of knowledge, making group management

Above: Statistics from those who did the online quiz Right: Screenshot of ‘Online Avalanche Course’

Recreational Courses

Avalanche course participant numbers comparisons

Recreational avalanche course attendance continues to grow, especially the Avalanche Awareness level. The Southern Lakes region is a hot spot for avalanche education, as is Canterbury and Tongariro. Participant numbers from external provider run courses (other than NZMSC branches), also continues to grow without any impact on ‘Branch’ run courses.

As we see more people heading into backcountry areas, it is encouraging to see a similar increase in those willing to gain more avalanche skills.

These trends are mirrored by statistics reported by the Canadian Avalanche Association (CAA).

265

230

218

31

AA

26

22

BC

AA

2011

BC

AA

2012

BC 2013

MSC Avalanche course participants 2011-2013 2011

2012

2013 75 71 65

61 57

55 54

39

37

35

36 30

2828

9

5 0 0

AA

BC

Tongariro

2

0 0 0

0

AA

14

12

11

BC

Taranaki

AA

6 0

BC

Canterbury

9

0 0 0

AA

BC

Wanaka

16

0 0

AA

BC

Wakatipu

1112

10

AA

4

0 0 0

BC

Southland

AA

BC

External

Above: Recreational avalanche course particpant numbers by Region.

Key: AA- Avalanche Awareness Course, BC - Backcountry Avalanche Course.

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Education continued Professional Courses Stage 1 When we look at the participant numbers coming through the professional ‘Avalanche Management Stage 1’ course, it is a very different story. In both the short (week long) and the Semester based courses, numbers have been in steady decline ever since the Tertiary Education Commission (TEC) stopped funding this course. ‘Stage 1’ is an entry level qualification needed before gaining employment in the vast majority of ski patrols, and necessary when on the mountain guides pathway. It is very different from the ‘Stage 2’ qualification which is developed largely within the workplace.

This downward trend may have ramifications for Industry, and if this continues, it is not unlikely that we may see a skill shortage develop.

Combined NZ Polytechnics Stage 1 Participant numbers

2010

2011

2012

2013

77

41

45

43

35 28

20

Short

Semester

Courses

Courses

17

Stage 2 2013 saw 15 new graduates of the Stage 2 qualification. This was the largest number of graduates in any one year to date.

The flexibility of the course structure splits the learning and assessment parts of the course. Consequently, some will delay their exam for a season so they can better prepare. This may cause a type of back log or bottle neck of those wishing to be assessed in any one year. That was the case this season.

Click here for more Stage 2 course pictures

Above: The classroom sessions, where knowledge and bacteria were imparted to all. Photo: K. Offmann

Above: Choosing safe terrain, Jim Young walks the fine line. Photo: Gordie Smith

Above: Tony ‘Grom’ McCutheon staying focused on snow craft despite the obvious scenic distractions. Photo: Gordie Smith

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research - shear strength probe using shear vane // university of canterbury - mechanical engineering dept Research by masters students at the mechanical engineering dept of Canterbury University have continued initial work done

by Art Tyndall in developing a probe to measure the shear strength of layers within a snowpack.

The probe uses a hand-drill powered shaft which drives a shear vane attached to the end. A perpendicular hole is drilled into the snowpack, and rotational resistance is measured. This can be shown on a graph similar to a snowprofile.

Above: Associate Professor Keith Alexander shows the snow probe.

Right: Metering and range finding devices piggy back on the hand drill.

Below: Extension shafts and alternate shear vanes shown.

The latest version is able to be easily transported, and developers now seek people/operations to verify field measurements made by the device. To get more information or be involved with this field testing stage, please contact Keith Alexander by email here keith.alexander@canterbury.ac.nz

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research - avalanche mapping using rock striations // simon morris Simon Morris is the Snow Safety Research Officer at Porter Ski Area. Here he explains techniques used and results found from his work in mapping historical avalanche activity at Crystal Valley.

Historical Avalanche Events Porters Ski Area has begun a development, part of which will include expansion of the current ski area into the neighbouring valley. The expansion requires developing a new avalanche management programme that will meet the requirements that were defined by the Selwyn District Council and the Department of Conservation. One of the things we need to investigate to meet these requirements is the history of avalanche events within Crystal Valley. We have accomplished this by looking at historical photographs, collecting personal memories, together with evidence of vegetation and erosion processes.

Historical photographs A collection of old photographs showing historical avalanche events within Crystal Valley were collected.

These photographs were documented and examined to see if the avalanche event(s) provided any additional information about the avalanche paths and especially their runout zones.

Personal memories We found only a few personal accounts of large avalanche events within Crystal Valley. The foremost, was from the ‘Big Snow Storm of 1992’ when over 4m of new snow was deposited on the ski area over five days. Accounts from two staff members that skied through Crystal Valley near the end of the season reported seeing avalanche debris near the ‘Ski Lodge’.

Vegetation As there are no beech trees (Nothofagus) at our end of the Craigieburn Range we were unable to use these to

determine any old historical avalanche events. Searching for evidence of impact damage on the smaller vegetation like bushes and the undergrowth was problematic as we could not determine whether the cause of the damage was from wind or avalanche.

Erosion Processes We surveyed the lower Crystal Valley riverbed searching for avalanche striations and abrasion marks on the rocks.

Avalanche striations are created by the slow scouring action of rocks caught beneath the avalanche debris as it advances downhill. Striations are typically observed in the bedrock, leaving fine straight parallel grooves that illustrate the alignment and direction of avalanche debris motion. The riverbed below the elevation of 1,000 m was not searched as the density of the vegetation suggests that no large avalanches have made it past this point for a very long period. Only rocks along the outer edge of the riverbed were searched to reduce the likelihood that the erosion processes or the abrasion marks were cause by the river.

The lowest evidence of avalanche striations found within the Crystal Valley riverbed was a large boulder located at an elevation of 1,067 m (see Figure 1 - Blue arrow). This boulder was approximately 115 cm x 90 cm x 65 cm (L, W, and H) in size. A second slightly smaller boulder with avalanche striations was also found nearby. Both boulders were fully exposed from the ground and their striations were not parallel with the riverbed, but offset by 45°. We believe that these boulders are not in their original positions from when the striations were created and should not be used to

Figure 1

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illustrate the maximum historical avalanche event. The age of the avalanche striations on both boulders is not known; however there was new lichen growth over the striations.

Some lichens, like Crustose thalli, which are found on boulders in the Craigieburn Range, have a very slow, radial increase growth rate of between 0.1 and 3.0 mm/yr. It is estimated that some of the avalanche striations could be between 20 and 40 years old based on the size of the lichen.

The lowest genuine evidence of avalanche striations was found at an elevation of 1,085 m (see Figure 1 - Purple arrow). In fact, there were a cluster of three boulders all with avalanche striations within 10m of each other. These three boulders were embedded in the ground and the striations were all parallel with the riverbed, suggesting that they had not moved from when the striations were formed. Again it was very hard to tell the age of the avalanche striations on these boulders, but new lichen growth was again found over some of the striations. The lichens were larger compared to the lower boulders and might suggest an older age of the avalanche events. Another boulder location at an elevation of 1,087 m showed evidence of multidirectional avalanche striations indicating that perhaps multiple large avalanche events have affected this area (see Figure 1 - pink arrow).

Document History The largest recorded avalanche event for 2013 in Crystal Valley was recorded from an avalanche path known as ‘Mainline’. This avalanche event was well documented as part of the development phase. The crown wall was 718m wide; covered an area of 29.5 hectare; had a total length of 1,984 m with a minimum elevation of 1,169 m and a total mass of 50.6 thousand tonnes (see Figure 1 - Orange line and arrow). The distance between the recorded maximum runout and the lowest evidence of avalanche striations

Above: The lowest genuine evidence of old avalanche striations found, you can clearly see the avalanche striations on this boulder.

in the riverbed was 572m, suggesting that avalanches have run a lot further than what we have seen during the development phase.

Fresh evidence of vegetation impact damage caused by the Mainline avalanche event was found. An old snow totara bush (Podocarpus nivalis) was badly damaged by the right flank of the avalanche event that was located on a hillside 22.5m above, and a distance of 55m away from the streambed (see Figure 1 - Green arrow).

In addition, fresh evidence of abrasion marks was found on rocks caused by the Mainline avalanche event. Abrasion marks are usually found on the side facing the onward flow of an avalanche and are caused when two rocks collide with each other. Rock transfer is found after an event and is usually a fine white rock dust.

The lowest evidence of abrasion marks in the riverbed was found on two separate boulders at the same elevation of 1,207 m. These fresh abrasion marks were between 3 and 7 cm in length. Between the elevations of 1,212m and 1,216m there was a cluster of 10 large boulders. These were no smaller than 30cm x 30cm x 30cm (L, W, and H) in size, and had been rolled down the riverbed by the Mainline avalanche events. All these boulders had numerous abrasion marks on them.

A single, very large boulder located at the elevation of 1,248m, with an approximate size and weight of 1800cm x 1800cm x 1500cm (L, W, and H) and weighing 12 tonnes, had been flipped 90° down the riverbed (Map - red arrow).

This boulder was covered by a large number of abrasion marks and fine avalanche striations.

Above: Close-up view of multidirectional avalanche striations, likely evidence of multiple avalanche events.

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information is king - integrating infoex at the remarkalbes ski area // Mark Austin Mark Austin is an IFMGA Mountain Guide and the Snow Safety Officer at the Remarkables Ski Area , Queenstown.

A cornerstone of a snow safety programme hinges on the supply of quality information. If you have little, it’s tough going. If you have a lot, then with a good filter you can see what is relevant and discard what is not. ‘Quality’ comes from how complete the information is, the frequency and the timing of when you receive it.

We often move quickly between periods of having a good amount of relevant information, to lots of irrelevant information, to times of information drought. This can be moderated by the sharing, and pooling of information between neighbouring operations. Our INFOEX system allows this to happen on many levels, in both summary and more detailed forms.

Recent ‘large scale’ examples of information sharing have been the national collaboration to update the Ski Area Management Safety Strategy (SAMSS), and the activity safety guidelines produced by the Heliski Operators Group.

Our industry is more mature and coordinated than many would believe, and is certainly well ahead of other nations

in this respect. The INFOEX system is a good example of this.

INFOEX – External use Sharing safety information should be endemic to our industry, and it largely is, when we have the time! This is the key challenge we all face. The benefits of access to relevant, concise, and accurate information is not in question, but often, other time critical operational duties make it hard to spread the word outside our own organisation until the end of the day.

While some safety data is only of critical use if shared quickly, most information can be used in a more reflective way. The INFOEX system allows for the use of these two different methods in a seamless way, and if you’re smart, you can arrange data entry around your operation’s other needs.

Since the redevelopment in 2012, we can now edit any entry we have made into INFOEX. If something is so vital that it needs to be shared right away but time is tight, we can enter a quick summary message that we can come back to and complete later. An example would be an entry that groups many avalanche observations together, so that other operations can get a feel for what kind of results we have had that morning. Later, when time allows (new snow days will nearly always be chaotic till mid-afternoon), we can enter our complete avalanche observations, transferred from our paper recordings and obliques. This is something that can be handled by admin or clinic staff, keeping Patrol out in the field, where they are most needed.

Above: Choose a ‘safe’ and representative slope to collect your data. Mark ‘Tubbs’ Evans employing extra caution.

Right: Pete Witworth applies a filter whilst searching recent avalanche results.

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INFOEX – Internal use There is debate that some operations due to their location, stand to benefit more than others from sharing information through the INFOEX system. If you are alone or an operation located at the outskirts of a region, the main use and benefits of entering your snow safety observations will probably be ‘internal’. We have been really getting a grasp on this function which in itself is a compelling argument for using INFOEX, and we are starting to see benefits within our organisation from the regular entering of complete observations.

As I am (slowly) coming to grips with INFOEX functionality, I am seeing greater benefit for my forecasting. We often leave the hill with a reasonable idea of what our snowpack is doing. We have comprehensive weather, snowpack (including snowpit images), and avalanche observations.

These are now available to us anywhere with internet, on almost anything with a web browser. I can now catch up on our region’s current observations over my weekend before returning to work. If we have a storm cycle, I can look up our pre-storm weather data, picking up on things that may have had little relevance at the time of recording.

As the INFOEX gets older we are only getting started on what we can use it for. We have 15 years of snow safety data stored in ‘the cloud’, and we are looking at entering more from old weather field notebooks so our history would extend back at least another 10 years. I know there are other operations which have even older historical archives.

Those dusty books on the shelf are doing nothing, but if converted, their data could provide a better indication of long term trends and patterns .

The ‘export’ function allows us to use the data in planning for the future. This will likely be helpful for a diverse range of usages such as snowmaking, ski field infrastructure (buildings and lift lines), short term avalanche return periods, or explosive use, cost, and their strike rate (% a nil result occurs upon delivery of a charge). Another potential use could be to link weather and avalanche observations to generate some great case studies and training resources.

Naturally, you cannot expect to get good results if the quality of the entered data was poor, or only done on an ad hoc basis. But by using consistent recording standards and routines, your data will make more sense for you and your neighbourhood colleagues, both now and in the future.

I would encourage you to delve deeper as we have here at the Remarkables Patrol, and see how INFOEX data can work for you. It’s opened our eyes to another significant tool when monitoring and planning around snowpack issues. Sure there will be questions, but the INFOEX help line is always open for business, right Gordie?

EDITORS NOTE: That’s right Mark, always open! It is also good to see you and other operations making use of the “Hazard Analysis” page too. We hope to get more industry feedback as this is more widely incorporated within operations daily routines.

Below: Sample report in pdf format, produced from “Hazard Analysis” page in INFOEX

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new Backcountry avalanche advisory danger boards We are developing a new design for the Backcountry Avalanche Advisory boards. These are positioned at ski areas, mostly at common access points into the backcountry.

Most of the layout is complete, and has incorporated the more detailed, 3 separate elevation danger ratings. The individual danger rating slats are changed to match the daily advisory. We have four alternatives for the messaging that appears on the slats, and would like your feedback. Rank the four versions in order of effectiveness, and provide your reasons.

YOUR FEEDBACK NEEDED

Either email your response to

info@avalanche.net.nz

OR

click HERE to view and vote online

Click on the images below to view higher quality versions - this will open them in a browser Version A: standard short message

Version B: skills needed message

Version C: Large signal word and number only

Version D: Very large number only

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Avalanche.net.nz Website statistics Between June 1 and September 30 2013, approximately 50,000 visits were made to www.avalanche.net.nz by over 16,600 people, with almost 186,000 pages viewed.

Encouragingly, the number of unique visitors continues to rise with an increase of 14.5% over the same period last winter.

The percentage of people viewing the website on mobile and tablet devices rose from 14 to 22%. This translates to more than 11000 visits.

3500

2013 Website Visits

2013 Website Visits

- Not surprisingly, spikes in visitor page views coincide neatly with storm activity. Previous daily total views until this year had peaked at around 900. This year’s early storm punched daily visits up over 3000 for a time.

3000

2500

2000

1500

1000

500

0 01/06/13

15/06/13

29/06/13

13/07/13

27/07/13

10/08/13

24/08/13

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07/09/13

21/09/13

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SOCIAL MEDIA Alongside the www.avalanche.net.nz website, we have a growing profile on social media sites. These are gaining a modest following, and serve to engage and build a community of backcountry users. They offer another way for the public to share their snow and avalanche observations. Here we describe how we use the different mediums, and what kind of following has been generated.

Facebook - www.facebook.com/NewZealandAvalancheCentre Aside from general interest posts, images and related news, we update Facebook when avalanche warnings move to HIGH. We also repost/share news and observations from the field. A breakdown of those who follow us on Facebook is below:

YouTube - www.youtube.com/user/nzavalanche

Twitter - www.twitter.com/NZMSCavalanche

At both ends of the country in Tongariro, and in the Southern Lakes, we have had regular video field updates on conditions. Our intention is to have these weekly, and also at times when we need to get special advice out to the public. The Avalanche Centre’s videos have been very popular, and have been viewed more than 10,000 times. Field techniques and guidelines on how to perform snowpack tests are always popular.

Any posts on Twitter also get directed and posted up to our Facebook page. We use this to advise when danger levels rise to HIGH. People who follow our Twitter feed, can get automatic alerts sent to their phones as well as see this within Facebook.

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avalanche.net.nz //

regional forecaster summaries

Avalanche ‘forecasts’ are by far the most viewed pages on the website, but this year the introduction of the free online avalanche theory course proved very popular. The interactive ‘route finding exercise’ page rated as the 7th most viewed page on the site, with over 4000 unique visits.

The large spike in numbers viewing the ‘Craigieburn’ forecast in 2012 was caused by the page being embedded into another website. Anyone viewing that host site would have inadvertently been reported as viewing ours. Craigieburn does however remain our most viewed forecast area.

Number of unique visitors to each forecast area 12,000

2011

10,805

2012

2013

10,000

7924

8,000 7,348

7218

7198 6,588 6,107

6025

6,000

5,521

5,427

5,100 4,521

5755

4,634

4443

4,000

4223

3,593 3,223

3,063

2,945

3102

2,210

1,906 1772

2,000 1,086

1,303

1,704 1573

1,259 779

1,528 1047

1,113

1023

0 Craigieburns

Queenstown

Tongariro

Wanaka

Mt Cook

Arthurs Pass

Online Course route finding exercise

Mt Hutt

Two Thumbs

Ohau

Taranaki

Nelson

Key to Danger Scale Graphics: 5 Extreme 4 High 3 Considerable 2 Moderate 1 Low Report not updated that day No rating insufficient information No rating insufficient snow No rating centre closed for season

The Backcountry Avalanche Advisories produced by the New Zealand Mountain Safety Council continue to be popular amongst recreational users of alpine areas. This winter more than 16.600 people regularly viewed the forecast pages to seek advice via www.avalanche.net.nz.

The following regional summaries cover the period July 1 to September 30 2013.

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TONGARIRO

// Ryan Leong

Overview Winter 2013 was nothing short of a rollercoaster ride for most people in the area. Winter arrived when it should have been autumn, spring sprung when it should have been winter, and then back to winter when it should have been spring. Throw in a few 100mm+ rain events, some interesting lemming-like behaviour by ill prepared backcountry users and there you have it.

There were even some nice turns to be had in between it all.

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Above: Panorama of avalanche debris from the Tongariro Headwall slide path. Click image to view larger version. Photo: Ryan Leong

It began with a promising start. A cold South Westerly system coated the entire central plateau with snow at the end of June. 30-50cm down in National Park village saw people ski touring around town. This also brought the first natural cycle to the region with numerous slabs up to size 2 observed.

The next major system rolled through from June 19-22 keeping everyone’s excitement levels up. Once again snow fell to low levels across the central plateau and thanks to the late May storm things were now well at threshold up high in the region. Several naturals were observed with one being a size 3 out of the Mangaturuturu glacier. At this stage both of the significant snow-bearing storms had been predominantly from the South – South West giving significantly more coverage in Southern parts of the region.

This was a pattern that was set to continue for most of the season.

A series of facetted layers formed around buried rain crusts during the early months of the season, but for the most part, they were sufficiently isolated beneath a series of strong supportive ice lenses. Cautious eyes watched these layers, but whenever they were within triggering range, high pressure systems would block any potential loading.

The warmer temperatures of July saw these layers quietly fade away.

The storm during July 11-15 gave the eastern side of the plateau a good covering to low elevations with a SouthSouth Easterly front. The Desert Road received more than 1m of snow on it by the end of this event. On July 15 several size 3 naturals occurred on the South Western flanks of

Ruapehu threatening Turoa ski area. These all appeared to have failed within the storm snow and run on a slick melt freeze crust. One other event to note from this period was a size 2 slab which was triggered by a snow groomer (Va) at Turoa ski area. This slope had been tested with explosives 24 hours previously with no result; however the groomer taking out the support from mid – lower slope produced a solid result. No damage was sustained.

Late July through to early August was dominated by blocking high pressure systems and mild temperatures. By this stage most areas except for the SW were (and are still) looking a little thin on the ground for snow compared to seasonal averages.

Mid to late August saw incremental top ups from all bearings of the compass, and more consistent avalanche activity both naturally and controlled. One notable event was a size 2.5 slab released by explosive that stepped down three times (all within storm weaknesses) and pulled back up onto a 24 degree slope.

During a West-South West storm cycle in the last few days of August there was another groomer-triggered vehicle accidental - this time at Whakapapa. Upon the groomer’s second pass along a CAT road, the slope above was triggered resulting in a size 1.5 slab which buried the CAT up to just above the level of its tracks. No damage to the CAT was observed; however it did require digging out by another machine.

The start of September marked the start of the snowpack decline for the season. Despite the odd modest snowfall,

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there were two main standouts for September 2013, rain and a spate of behaviour from backcountry users akin to lemmings.

Firstly there were two significant rain events: September 10-13 saw 104mm recorded, followed by a further 168mm from September 20-24. Waterfall holes and large creep and glide cracks opened up making some slopes appear glaciated, but there was surprisingly little associated avalanche activity for such a deluge. This was due to the fact that prior to these rain events the snowpack was in a well established melt freeze cycle, so drainage channels formed very quickly.

Secondly, the lemming-like behaviour. This was a combination of a lingering windslab instability, ice glazed ridge tops, and a number of people lacking the most basic backcountry skills, who appeared to follow blindly over cliff bands. A 40cm windslab had formed lee to the West Âź on September 14 which remained reactive to human triggering for a few days on specific terrain features. This problem was localised to the backcountry area surrounding

Turoa. On September 16, Turoa ski patrol were responding to a backcountry injury in the Mangaehuehu glacier (popular and accessible from ski lifts with a traverse), where a snowboarder had ridden (fallen?) off a cliff triggering a size 1 slab, injuring his back in the process. While the rescue was taking place another person hucked (fell off?) the same cliff landing and triggering another slab narrowly missing the rescuers. Further observations showed even more people falling of the same cliffs and triggering yet more slabs despite watching others do the same. The Turoa crew were glad to see the end of that backcountry instability.

To wrap it up, the 2013 winter season has been characterised by: -less avalanche activity than normal (99 recorded avalanche observations on the INFOEX as at 30 September) -less large scale rime events than normal (a good thing) -A couple of involvements (not such a good thing) -An isolated, but large natural cycle (a scary thing) -A bit of rain in September (not such a good thing) -Some sweet skiing in between it all (an awesome thing‌)

Above: Accidentally vehicle triggered slab. This groomer had to be dug out by another machine as the debris over ran the tracks. Photo: Ryan Leong

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TARANAKI

// Todd Cations-Velvin

Overview It has not been a bad season for snow users, with the local ski area managing quite a few open days during and after the two big storm cycles hit the mountain. It does seem like the winter has passed in the blink of an eye. With such warm settled weather in the region, shorts and t-shirts made an appearance as early as August.

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Weather The weather didn’t really play ball for Mt Taranaki this winter, with only a couple of reasonable storms producing significant snow fall.

The first significant weather system that rolled through in July brought plenty of snow to low levels, allowing the local Manganui Ski Field to open for the first week of the school holidays under beautiful blue skies. The Southerly storm produced around 50cm of snow at 1200m. A common theme for Mt Taranaki this winter was the rain that followed closely behind the storm cycle, which had a dramatic effect on the lower mountain snow pack.

As we headed into August the weather took a turn for the better, and if you enjoyed gardening, the mostly fine settled spring conditions would have suited you just fine.

One last significant snowfall hit the mountain at the end of August and into the start of September. This brought southerly snow to low levels, and great skiing for the locals.

September did little to add to the snowpack. A combination of rain and warm weather, with the freezing level sitting about the summit on most days, saw a very rapid rise of the snow line.

lower elevations and destroying any weakness within the snow pack. Consequently it provides slick conditions on the mountain with over night freezes. This can lead to other issues with the amount of rain causing wet avalanches.

This past winter however we saw no large wet avalanches triggered by rain events (no reported avalanches).

Moving into spring, the snowpack started to disappear very quickly, and minimal snow currently existed across the mountain, but for the summit area.

Conclusion Good on the 12 people who took up the opportunity to enrol on the local avalanche awareness course following last year’s avalanche incident on the mountain.

It’s been a mixed bag of a winter for Taranaki, but it is promising to see people taking the right steps towards looking after themselves in the alpine.

Be safe in what you do and seek knowledge where knowledge can be gained to enrich your life.

Avalanche Activity The few storm cycles we received this winter produced small size 1 and 2 avalanches. These were confined to surface layers, or within the storm snow. There were no reported incidents.

Snow pack The early season snowpack through June was thin, with the snow line sitting around 1600m. No significant weakness existed within the snow pack at this time due to the warm daytime temperatures consolidating what snow we had with over night freezes.

During the two most significant storm cycles we had in the region this year, we saw instabilities within the new snow due to wind and temperature change during the storm. Both storms provided a significant amount of snow (around 40-50cm plus) with strong wind transportation.

This created large areas of wind slab, with the potential for large avalanches.

In Taranaki we seem to experience rain and a warm up on the mountain on the heels of the storm cycles. This can be one or two weeks after the storm, and usually has a significant effect on our snow pack, diminishing the snow depth at

Above: Fully Equipped - MSC Avalanche Programme ‘Hobbie’ approaches one of the backcountry access gates at Turoa Ski Area on a splendid Ruapehu day. Photo: Gordie Smith

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NELSON LAKES NATIONAL PARK

// Matt Wilkinson

Overview We have now completed five years of forecasting for the Backcountry Avalanche Advisory in the Nelson Lakes National Park. This winter will be remembered or hopefully quickly forgotten for having the leanest snowpack since this avalanche forecasting service began. Consequently, a normally active and vibrant ski and snowboard touring community has been very quiet. There has not been a sustained period of time at any point during this winter that the National Park offered sufficient connected snow cover at mid-elevation to allow for anyone but the hardened enthusiast with access to an industrial supply of p-tex to get into either the local backcountry around Rainbow Ski Area or the other regularly frequented backcountry ski and snowboard touring locations around the National Park.

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Weather The winter started in most parts of New Zealand with a hiss and a roar with late June storms delivering substantial snow volumes. In Nelson Lakes, little did we realise it at the time but this was also to be our biggest snow fall of this winter.

Between 22-25 June, 30 to 40cm of snow fell which was accompanied by winds of 150 to 160km/h from the southerly quarter. The large volumes of snow that fell in Canterbury did not push through to Nelson. Consequently, the post-storm snow cover was very intermittent at all elevations as is evident in the photo below.

Wind damage occurred to facilities at Rainbow Ski Area.

The toilet block that has weathered many southerly storms was blown off its foundations.

During early July we experienced a period of very high freezing levels and rain for the time of year, 3000m not being unusual. This kept the snowpack comparatively

warm and capped it with a melt/freeze crust. In July we also experienced intermittent colder and warmer storm fronts with very unsettled weather for most of the month.

The lack of any appreciable snow was more than a little frustrating.

It took until August 11 to see any significant snow fall, with a storm of 25cm or so across the park which contributed to avalanche danger level reaching ‘considerable’ for a 24 hour period. August continued in this vein without any significant snow accumulations, on any aspect, due to the variety of storm wind directions as well as variable freezing levels during the abundance of unsettled weather.

September 10-11 saw a very strong northwesterly produce large amounts of precipitation in the park. Freezing levels hovered around the 1800m mark early in the storm, driving rain into lower elevation snowpack. This produced the

Photo: Courtesy Rainbow Ski Area

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highest avalanche danger in the park at the time of writing this report.

Warm rain to all elevations started on September 20 and persisted for three days. Rainbow Ski Area was closed for the season on September 23 and unsettled spring like conditions have persisted since.

snow ablation and closed Rainbow Ski Area for the season.

The transition to a spring snow pack is now complete at all elevation. Large climax spring avalanches to valley floor, which can often be problematic in the upper Western Sabine, are unlikely to occur this spring due to a lack of total snow accumulation during this winter.

Snowpack A large percentage of the winter snow pack fell in the last week of June. This storm brought 30 to 40cm of new snow, then received the most ferocious of wind hammerings that I have experienced in my five year history of working in this programme. Given that this storm formed an intermittent thin snow cover, capped with a brittle rain crust, there was concern about the formation of a persistent and deep faceted layer that would make a poor bond for future layers.

This did not eventuate and the snow pack was repeatedly subjected to rain to high elevations. Therefore the majority of the snow pack remained reasonably stable without any persistent weaknesses within it.

Avalanche Activity It is believed that the first substantial avalanche cycle occurred during the late June storm prior to this forecasting programme having started. Since then, despite having periods of ‘considerable’ and one period of ‘high’ danger, it has been a difficult winter for observing avalanche activity. This was due to the lack of backcountry access, very marginal conditions around Rainbow Ski Area, and long periods of inclement weather around the major storm cycles which limited helicopter access into the park.

In July to late August most avalanche danger was due to small wind slabs lee to the storm’s wind direction which would stabilise quickly due to a lack of snow volume and a reasonably warm snow pack. The most pronounced of these was on August 11 when a south easterly produced 20cm of snow that caused the avalanche danger to be ‘considerable’ for a time. This was due to increasing wind speed and rising freezing level during the storm causing a pronounced density inversion.

There were a number of episodes of rain to upper elevations increasing danger for a time. The most pronounced rain on snow event for July and August occurred on 28 August 28, causing the snowpack to be saturated at all elevations.

September saw a number of significant storm cycles. The first, on September 4 from the south west and created considerable danger on north east aspects above 1900m.

This was due to somewhat questionable bonding to the melt/freeze layer formed at the snow surface on August 28.

The second storm from September 11-12 came from the northwest and created a high danger above 1900m due to wind slab formation and considerable danger below 1700m due to a loose wet problem. This was the only time during this winter that high was recorded in the danger scale.

The third storm between September 20-22. Substantial quantities of rain fell during this time that accelerated

As a consequence, the avalanche occurrence section of the advisory has for the majority of the season shown either ‘none observed’ or ‘no observations possible’.

Travel Advisory Substantial snow cover on eastern half aspects will continue to see increasing avalanche danger during times of warm air temperatures and high solar radiation. Rain and warm temperatures will also accelerate snowpack creep and glide which will see a continuation in ground release wet slabs during spring that have been observed during late September. Caution will be required on solar aspects during the afternoon when air temperatures are high and during rain when the snowpack becomes unsupportive on skis or while walking. It will be important for people walking in the valleys to remember that there is still significant snow in the basins above. Most caution will need to be exercised during intense rainfall to high elevation.

Concluding remarks So ends another season of staring at weather forecasts and looking at meteorological data from the Mahanga data logger. Normally this is well balanced with poking our heads in the snow and getting some ‘real’ information from real observations. The lack of backcountry access this year has meant that a larger percentage of the information to determine avalanche danger has been from our continued access to the NIWA Mahanga weather station and the Rainbow Ski Area Davis weather station.

Thank you to those organisations for their continued support of the MSC’s Backcountry Avalanche Advisory for Nelson Lakes.

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ARTHUR’S PASS NATIONAL PARK

// Drew Gibson

Overview 2013 started similar to the 2012 season with a big storm in June, but things quickly turned warm and rain began to fall in the Arthur’s Pass area. This kept the snowpack in a melt/freeze state and limited to above 1550m for much of the season. Small top ups of snow did occur, but big rains dominated.

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Weather The massive SE storm that hit the South Island midJune struck the Arthur’s Pass area with severe gale winds and 3-5m of snow. The high winds completely stripped windward aspects in the alpine and high alpine, making for a thin early season.

Precipitation picked back up in early July, but it was far too warm. The total rainfall for the month was at least 300mm, but this number is a rough estimate due to the rain gauge getting blown over multiple times despite hardened anchors.

By August we had hoped that the rain would be a thing of the past, but once again it picked up delivering over 100mm across four days.August received ~210mm of rain which was less than July.

September started out fairly nice with high pressure and pleasant temperatures, but by the end of the first week it was obvious that it would not hold. A powerful Westerly system slammed into the Divide on September 1 being carried by gale winds and loaded with moisture. More than a metre of snow was forecast for the area, but the temperatures looked too warm to produce any snow. By mid-day on September 12 more than 350mm of rain had hit. There was light at the end of the tunnel though, as the system was on its way out, a Southerly element came into play, dropped the temperature and snow fell as low as 1000m. The Strong to Gale force winds continued from the NW during this fall and made measuring new snow depth difficult. Only 11cm was recorded at Temple Basin, with another 15cm in the next 36 hours, but obviously more snow had accumulated.

Another burst of rain hit again in the last ten days of the month bringing September’s rainfall total to 538mm and to 1048mm for the season.

Snowpack Two words can accurately describe a large portion of this season: melt and freeze. Although there was plenty of snow in the high alpine regions, the lower alpine regions suffered all season, and fell victim to warm temperatures and rain. The SE storm that came in during mid June was loaded with colder, low density snow that refused to stick to anything and was immediately blown away. Things got warmer at the beginning of July and the snowpack took

a heavy rainfall causing the danger level to rise to HIGH. Snow did fall in this event, mostly as a graupel layer that was up to 50cm thick in some places. This layer surprisingly remained unreactive and eventually broke down. Continued top ups of snow throughout July bonded well to the old surfaces, and most reactive snow was isolated to during the storms. The snowpack lacked any freeze cycles due to rising temperatures, and after a burst of rain became nearly isothermal. Though this was worrying for us, the snowpack remained solid and didn’t show any signs of instability other than for the afternoon loose wet activity.

The snowpack became capped with the diurnal temperature shifts requiring careful timing for backcountry travel.

As the rains continued, the snowpack remained in a melt/ freeze state and pretty boring. After a burst of rain and snow in the high alpine, the snowpack let loose on 16/8 with a widespread wet slab, loose wet cycle, but immediately returned to the melt/freeze.

After the rain on September 11, the snow that fell managed to stick despite gale force winds which had accumulated to over a meter on aspects lee to the NW. Cooler but still mild temperatures allowed this snow to bond.

Avalanche Activity The wet, natural cycle on August 16 was by far the largest of the season, with slides of size 2-3 pulling out on steeper, unsupported terrain. Mt. Phipps stayed fairly reactive this season with multiple size 2-3s running during rain events and with some debris piles over 3.5m deep. Wet loose slides were the common occurrence. Some days such as August 13 yielded skier-triggered size 2 wind slabs in the Mingha Valley.

Concluding Remarks It was another challenging season for ski fields and backcountry travelers alike. Managing the uncertainty of an isothermal snowpack is a challenge, and this year showed us that isothermal does not always mean unstable.

I would like to thank the staff at Temple Basin ski area and the Temple Basin Ski Club for sticking it out despite the adverse conditions and still making it a great and memorable season.

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Above: Todd Windle and Elliot James work towards opening terrain at Temple Basin this winter. Photo: Drew Gibson Below: Cleanup begins at Treble Cone after a large slab was triggered by explosive on their summit slopes during control work. Photo: Gordie Smith

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craigieburn ranges & MT HUTT

// brad carpenter / jason konigsberg

Overview The extent of the Mt Hutt forecast area was changed this winter. The outlying ranges of the Taylor and Arrowsmith ranges were taken out of the forecast area, so the Mt Hutt forecast would be more accurate and concentrated on the area of greatest backcountry use. Two forecasters shared the role of issuing both the Mt Hutt and Craigieburn backcountry advisories. For a large majority of the forecast days, conditions were similar between the two forecast areas. Often times any variations were that of precipitation totals but the snowpack, general weather pattern, and primary avalanche problem were, for the most part alike. Brad Carpenter and I split the week, and we both felt that we were able to remain fresh in the writing of the forecast and help each other to point out differences on either side of the range. This was especially so during the first avalanche cycle, where spatial variation over the range was great.

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Weather In general, 2013 was a lean year snow wise but not in the way of precipitation. Temperatures were way above normal and you couldn’t even say that a degree or two would have made a difference, in turning the rain to snow.

The winter started off with a boom, with the big mid-June southerly storm, and then quickly turned into a bust with very little accumulating snowfall again till late August. If it wasn’t for the big June southerly there wouldn’t have been much skiing at all this year.

The storm over June 20-23 dumped from 1 to 1.5m across the range with strong to gale southerly winds. The higher end totals were recorded at Mt Hutt and the Southern Craigieburns. The most important factor in a destructive avalanche cycle following this storm, was the easterly that set-up over the South Island on June 16 and 17, as 30-50cm of snow fell with warm temperatures affecting areas over 1500m.

The next major storm system to roll through the area occurred just as ski areas were getting ready to open with top to bottom powder conditions and would be a sign of things to come. This northwest storm over July 4-6 precipitated 50mm of rain to ridgetop. Luckily this storm went out cold and salvaged a few opening days with up to 10cm of snow.

For the rest of July and August temperatures were warm with the occasional northwest rinse and little snow. The last week of August and first week of September were some of the best weeks of the year as the pattern changed and we received a few quick moving but vigorous cold fronts from the south that gave us much needed snow to lower elevations.

Following the winter teaser, things went back to normal, temperatures rose and it rained again. As of writing this report on the 30th of September fifty percent of the ski areas have closed up shop and most Canterbury areas will be closed by the 5th of October.

Snowpack The snowpack was shaping up nicely in early June, with very little snow on the ground to facet. It was looking like the first big storm would fall on bare ground setting us up nicely. Unfortunately the leading edge of the storm that brought the big southerly also gave us a very warm snowfall a few days prior. This normally would be great but a slight break in weather between the easterly and the southerly part of the storm saw the surface snow freeze into a thin crust and some faceting quickly occurred underneath the melt/freeze crust. This set the stage for one of the more prominent avalanche cycles that the Craigieburn and Mt Hutt Range has seen.

It is worth noting that there was a large difference in stability in the northern part of the range where very few post storm avalanches were triggered. Much pondering has gone into what snowpack characteristics were different.

Main differences were the northern mountains may have had a higher freezing level and had much less snow with the easterly portion of the storm contributing to inconsistent snow cover. The melt/freeze crust was also quite a bit thicker, possibly inhibiting quick facet growth beneath it.

The last theory is a simple terrain theory in that terrain where avalanches occurred, were large uninterrupted start zones that were right in the bulls-eye slope angle. Many northerly slopes on the northern side of the range are steeper and more confined terrain features leading to more frequent natural shedding during storms.

The persistent slab issue lingered in our minds for a while and showed alarming stability test results but activity waned quickly. The rain begun with the month of July and quickly wiped out any weak layers and consolidated the snowpack. Throughout the season we had a few thin crusts and facet layers near the surface that may have caused a problem if buried, but the rain always seemed to roll in and cure all snowpack problems. After the persistent slab problem subsided avalanche concerns centred around any new snow that fell, and wet loose activity as warming occurred following any storms.

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Avalanche Activity Very few backcountry avalanches were reported over the 2013 season, and there were no reported injuries or burials in the backcountry of the Craigieburn or Mt Hutt Ranges.

All reported incidents were at the ski areas. This paradox was probably due to backcountry travellers not being out during the height of instability because of poor weather, good ski conditions in the ski area, and hopefully conscious decision making.

The first series of avalanche incidents occurred on June 23 when Mt Hutt and Porters ski area explosively triggered avalanches to Size 4. Extensive damage occurred around Porters base area and Mt Hutt’s triple chair was damaged beyond repair due to these avalanches.

The other two incidents involved ski patrollers in the Craigieburn Range. The first of these was on the 14th of July as ski patrollers at Mt Cheeseman were controlling newly formed wind slabs above their access road. A patroller was taken for a 300m ride when he triggered a wind slab which broke above him. He suffered lower extremity injuries but luckily did not go for the full extent of the ride which would have led to a deep burial as the avalanche ran 650m.

This was a size 2 on an east facing slope with a starting elevation of 1600m.

The second patroller involvement was at Craigieburn Valley Ski Area and occurred on the 29th of August. The patroller involved set out at 3:00pm to evaluate and re-open northerly facing terrain that had been closed all day due to 28cm of previous snowfall and anticipated avalanche activity from solar radiation on the new snow. The patroller put a few ski

cuts in the upper start zone of a 39 degree northerly facing slope at 1750m. With no results on ski cuts and no other signs of instability the patroller started to ski the path.

After skiing for 100m the patroller was hit from behind by an avalanche that started as a wet loose avalanche, which then entrained dry storm snow. The patroller was taken for a 100m ride and was not buried or injured. This was a size 2 and ran at the new snow/ old snow interface which was a slick melt/freeze crust.

Concluding Remarks Thanks to all those that contributed to the avalanche advisory for the 2013 season. All the INFOEX data received from the ski areas is invaluable and helps to make for a more accurate forecast.

The snow safety team at Mt Hutt was always there to help as we often had question as to what was happening with their snowpack.

This year we made a big push to obtain observations from backcountry users by advising the public that they can submit observations via several different avenues.

Unfortunately participation is still minimal and we would hope to find a way to get more of the public involved in the future and provide input to their forecast. Overall, we feel we were able to put out an accurate and up to date forecast for the public.

Summary written by Jason Konigsberg

Above: Skier accidental slide from August 29. Photo: Jason Konigsberg

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AORAKI / MT COOK

// Trev Streat / Dave McKinley

Overview Hopes for a great winter after the big snowstorm in late June were soon dampened down by an extended period of unsettled and often windy weather. The first decent fine spell lasting more than a day or two did not arrive until the end of August when the weather seemed to settle down into a more normal pattern. There were fewer, smaller avalanche cycles than usual and ‘spring conditions’ affected the snowpack somewhat earlier than the official start of that season thanks to warm temperatures.

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Weather, snowpack and avalnche activity In late June, a notable southerly storm left 70cm of snow in the village with some impressively deep drifts in the lee of buildings. This was followed by a fine spell long enough to cause concerns about surface hoar and recrystallisation becoming a problem once buried. We didn’t have to wait long.

The ‘storm of two halves’ moved in on July 1.

The first half saw gale NW and 144mm of rain over three days with the freezing level peaking at over 2000m.

During half time on July 4, compression tests on the Ridge Glacier gave moderate SP results on buried surface hoar about 80cm down, but only hard broken results elsewhere on the old surface. Several size 3 avalanches were observed to have run-out to valley floor on the divide and North Ben Ohaus.

The second half brought around 240mm of rain to the village along with gale NW then SW winds and a drop in the freezing level. A few small fresh slabs were observed after this bout but it was difficult to tell if some of the other drifted-in debris of larger events, was from the first or second half. Despite searching hard, no trace of the July 1 surface hoar/facets were found, and for the rest of the season, any instability was confined to recent storm or wind drifted snow.

For the next six weeks the weather was uncharacteristically unsettled. Winds were often strong and there were frequent periods of light snowfall or rain. The freezing levels mostly sat between 1500m and 2000m but rose to 2400m a couple of times in July with the odd bit of snowfall that reached the village.

There were three avalanche cycles during this period.

Isolated slabs to size 2 ran up on the divide on 27 July following three days of strong westerly winds. Another cycle of similar sized slabs went a week later during a

four day westerly blow that dropped 43mm of rain in the village, and on the 23 July widespread avalanching to size 3 occurred. This one followed ten days of unsettled weather, and the larger slides stepped down into the 25 to 30cm of westerly snow laid down 13-15 July.

The only human-triggered slab that we are aware of for this season ran on 16 July when a snowboarder cut across the top of a convex roll on a NE aspect at 2300m. It was 20cm deep and about 20m wide and ran within the storm snow.

The rider rode off the slab and was not buried.

The September fine spell brought good weather and stability at last but on 8 September, NW gales, a high freezing level, and rain arrived again. There was an impressive thunderstorm on 10 September and by the time things cleared on the 14 September, there had been over 300mm of rain in the village and widespread wet snow and slab avalanching to size 3 on S and E aspects, with numerous smaller slides on other aspects.

Conditions for the rest of the month followed the usual spring pattern. There were brief periods of instability during precipitation or when things warmed up just after, but otherwise good stability with rapid settlement and bonding thanks to mostly mild temperatures.

CONCLUDING Remarks While the 2013 winter wasn’t the most exciting one for snow and avalanching we should at least be thankful that it was a reasonably safe winter with no lingering deep instability to deal with. Another plus was that despite warm temperatures and a pretty high snowline there was still a lot of snowfall up on the neves. Crevasses were well bridged all season, and the outlook for touring in the high mountains is good apart from walking in and out, in which case the high snowline and lack of avalanche debris down low will make for long stony stumbles en route to the goods.

Thanks to everyone who provided snow and avalanche information from around the Mackenzie area. As it’s a big

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area, snow conditions could vary wildly from one side to the other. Timely observations from different parts of the patch were a vital aid to forecasting.

Right: Dave McKinley puts his search dog through its paces on a mountain of avalanche debris at Mt Cook this winter. Photo: Dave McKinley

alpine and avalanche resources

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NZ Guidelines and Recording Standards for Weather, Snowpack and Avalanche Observations (2011, NZ) $30.00

Card Combo (both cards) $19.99

To purchase any of these resources online, please visit www.mountainsafety.org.nz/resources

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WANAKA

// Simon Howells

Overview Winter in the Wanaka region commenced with plenty of promise. We enjoyed an abundance of early snow as the result of a series of moisture laden Westerly storms. Unfortunately, the middle of the season was characterised by long spells without a snowflake to be seen. From early July until the end of August, the weather tended to be either, clear and cold, or we were enveloped in Easterly clag where you struggled to see past the tips of your skis. In September, a warm Northerly air flow dominated and produced far more rainfall than snow especially below 2000m.Despite the often challenging conditions, interest in backcountry touring remained high and when the fresh snow arrived, numerous participants would be quick to head out in search of good quality turns.

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Weather and snowpack By the end of May, a number of Westerly storms had delivered more than a metre of snow in the East of the region and considerably more to the West of the divide - the makings of an epic winter. In the first week of June, a moisture heavy NW storm arrived but ominously during the same period, the freezing level shot up to 1800m. The result of all of this was a widespread and very robust rain crust which became known as the ‘Queens Birthday Hard Layer’.

Once again we experienced an unusually warm ‘spring-like’ rain event in the early part of winter, a situation which seems to have become more common in recent years. In the aftermath of the deluge, hard rain crusts created ‘slide for life’ conditions in many areas particularly at mid and lower elevations (below 1800m). Backcountry travellers were being advised to carry ski crampons or even crampons and an ice axe - not equipment that would normally need to be carried at this time of year.

In mid to late June a couple of South Easterly storms ensured that this excellent potential failure plane was buried beneath a substantial amount of snow. The ‘tipping point’ was reached in early July when additional loading from Westerly storm activity led to a widespread cycle of avalanches many of which, stepped down to the rain crust.

From mid July into August the weather settled with long clear periods and limited quantities of precipitation.

In the second week of August, the weather was more unstable with light to moderate winds from the Westerly half and several small snowfalls. An Easterly flow developed in the third week of August and we were plagued by a number of days where the visibility was very poor and the winds were too feeble to push the cloud away. Fortunately, during this period it continued to snow - small amounts admittedly - but by this stage every fresh centimetre was welcome. In the final few days of the month, a Southerly flow arrived and temperatures dropped dramatically. An additional 10cm of wind affected snow fell on August 28.

September opened with a week where there was very little snow at mid elevations (1000 to 1800m) but 25cm above 2000m as the result of a brief Southerly storm. It was

mostly cloudy, temperatures were mild and winds generally light. We received 30cm of new snow at 2000m from NW storm activity between September 10-12, but this came in warm and wet, and tended to bond well to the old surface.

At lower elevations, this NW precipitation fell as rain with 30mm at 1200m. From September 12-18, the weather was cold and clear with night time temperatures between minus 5 and minus 9 at 1750m. With conditions such as these, surface hoar growth was a concern but the arrival of another warm NW system on September 20 saw further rainfall to higher elevations (at least 2000m), and the potential surface hoar problem was literally washed away.

More than 30mm of rain fell over three days at 1750m.

In the days following this rain event, we experienced a Northerly flow, mild temperatures and extended periods where the freezing level remained very high (2000m or above). These conditions created a situation where the rain saturated pack was not refreezing and therefore not regaining strength. Large glide cracks opened rapidly and buckling and folding were widespread. In the last week of September, a couple of clear nights produced shallow freezes (top 5-10cm), but the pack underneath remained unconsolidated to ground.

Avalanche Activity For the majority of the 2013 winter season, avalanche activity involving slides of size 2 or larger were very uncommon. Most of the occurrences reported were size 1.5 or smaller. Happily, there were no full burials or serious injuries recorded. Also, there were no reports of significant damage to structures or vehicles. There were no incidents that required a response from an outside agency such as Wanaka SAR. There was a marked increase in activity in early July when the Queen’s Birthday buried rain crust came into play. This crust had become deeply buried over the course of a couple weeks but the load had not reached a critical point. Several days of a NW storm activity which commenced on the 5th of July added enough weight to trigger a widespread avalanche cycle running on this crust. A number of size 2 and 3 results (both natural and controlled) were recorded during this period. In the weeks following this cycle, things

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settled down as further snow loading was limited. Over time, the crust began to break down helped by periods of warm weather.

Hazards normally associated with spring were an issue throughout winter this year. Periods of heavy rain combined with warm temperatures and high freezing levels were common. In the last two weeks of September, wet slab avalanches were a frequent occurrence particularly on solar (North facing) aspects between 1200 and 2200m.

Concluding Remarks The most remarkable characteristic of the 2013 season was the number of warm, wet storms that it produced and the unusual conditions they created. A major challenge in the future appears to be dealing with spring type hazards at any time during the winter.

I would like to thank all the members of the Wanaka outdoor community who provided me with information that assisted me in the preparation of the daily Backcountry Avalnche Advisory.

Above: Wanaka Backcountry Forecaster Simon Howells testing his August predictions.Photo: Gordie Smith

Above: Evidence of the late season heat affecting the surface layers during September. 2013 Stage 2 graduate Heidi Godfrey is framed within a large rollerball doughnut formed in the Southern Lakes region. Photo: Gordie Smith

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QUEENSTOWN // Chris Cochrane Overview One thing is for sure, you don’t need a heavy snow year to produce avalanches. Unfortunately we had an avalanche related fatality in our region this winter. This sad event came in a season where we have had a relatively low avalanche involvement rate.

Another season and another set of weather records, unfortunately not the records we like. Is all this talk of global warming true? Is it affecting snow levels? Or is it just the ebb and flow of another snow season? Some interesting facts have emerged from our season. I will lay them out for you, and you can be the judge.

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Weather Over the past few years there has been little to cheer about in the early season with most ski areas needing snow guns to generate a base for opening due to lack of natural snow.

Not so this year, with regular falls in late May and early June, the season showed a lot of promise. You have to go back to 2009 to get a better start to the season. Regular snowfalls continued and June was by far the stand out month.

Temperatures remained cold in the first week of July with a significant fall early in the month. Weather patterns changed from July 10 and the dreaded easterly flow began.

Temperatures began to rise and a ‘spring-like’ snowpack developed. July was the warmest and driest since 1909.

This pattern continued for the next four weeks with cloudy warm days and very few frosts. The Queenstown Winter Games struggled with the cloud and there were very few sunny days during this period. Snowfall was minimal with the region receiving 50% less rainfall than normal. The biggest snowfall was approximately 4cm.

It was late August before winter and snow returned, but precipitation levels were only moderate with the average fall around 10 to 15cm. The month finished as the warmest August since records began in 1878.

There was hope that September would yield some bigger dumps as in previous years. While temperatures remained cool and the snow stayed in good condition, snowfalls remained light to moderate.

By mid-September, most ski-fields were struggling with a fairly thin snowpack and the big spring falls failed to eventuate.

Snowpack As stated above, the early season snowpack was good with great coverage in the backcountry. However, concerns were mounting in early July as a strong temperature gradient had developed. This combined with the early July snowfall that buried surface hoar up to 40cm deep within the pack, meant that the avalanche danger scale showed ‘high’. Explosive control work was carried out on field and backcountry with very large results. The problem of buried surface hoar and

a weak snowpack structure was remedied by an increase in day temperatures and the development of a melt/freeze snowpack.

When heavier falls began in late August, the general snowpack was well settled and bonded, the only real concerns were within the moderate falls over the next few weeks. By mid-September warmer temperatures and a lack of snow saw creep and glide zones failing at ground, and an increase in wet slide activity, which has been the story through till the end of the season.

Avalanche Activity There were 13 people caught in avalanches this season resulting in one partial burial. Also two climbers were involved in events which resulted in one fatality. The small 5m wide avalanche had a crown wall of 20cm. The event occurred at 2000m on a Westerly aspect. Tragically the climber was swept off his feet and over rock bluffs. There was a ‘considerable’ rating risk posted for the day, due to 10 to 15cm of cold snow which arrived with a light SW breeze during the previous 24 hours. There had been numerous loose snow avalanches on the previous day, mainly due to overloading.

The morning of the event there were reports of widespread natural avalanches which had occurred overnight.

Temperatures were above average during the night, and this was considered the catalyst for the naturally triggered events. The climber was on a 40° slope at 8:30am when he triggered the slide.

Concluding Remarks The easterly flow over the country was put down to there being more high pressure systems than normal in the south of the country and more lower pressure systems to the north. This is not the first season where this has occurred and it appears to me that this is becoming more and more common. This type of winter was once rare. Over the past decade only the winter of 2011 passed without an easterly weather system of some kind. Whether this can be attributed to warmer ocean currents or global warming is a big question. I believe it is, but I hope I’m wrong!

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case study - cracking and persistent deep slab at the remarkables // Mark Austin Mark Austin is an IFMGA qualified mountain guide. He travels between hemispheres following the winter seasons, and is currently the snow safety officer at the Remarkables Ski Area in Queenstown.

Events of Monday 8th July 2013 Monday morning and the day started relatively well. We had received some snow out of the NW followed by a SW change. The weather was great for control work with good visibility and moderate winds. Control teams were out in some of our Primary and Secondary terrain. Explosive testing had produced little to no results from the first shots.

Then things started to get a little different. The control team on the Knoll Route, which protects the “skiers left” of our beginners lift and the Base Building, had extensive and deep cracking with a shot (7.50am) on the East Face path. The team continued to test the start zone with a

total of four separate shots, all 900g pentex cast primers.

No result. The team was concerned that the cracking had not alleviated the energy in the slope but decided it was not able to be triggered by skier and continued to finish the route and open lifts. The terrain remained closed.

Meanwhile on the Highway, two control teams were working on opening terrain on a similar aspect, elevation and terrain features. There were no results from the usual suspect through the start of the routes. I remember saying to my teammate Michel how relaxing a day it was compared to normal…The next shot was a double powergel into Imhoff’s Right (9.10am).

We didn’t hear the whumph due to the noise of the shot, but we felt the drop. Michel turned around and yelled. I don’t remember what but my eyes told me the story. The next path had run sympathetic to the shot producing a stepdown avalanche with a crown up to 2m deep. Big hard blocks and some rocks rolled off down the hill in the avalanche. My ski tracks to our “safe” spot were off down the hill as well.

Left: Avalanche release in “Imhoff’s left” path. Photo: Mark Austin

Once the adrenaline had worn off we started to think hard about the East Face. Same aspect, elevation, steeper slope angle and hanging over open terrain with the exit cat track from Shadow Chairlift beneath. More gear was delivered and a control team headed out. The terrain below

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was closed. It helped that the lift was down with a mechanical issue.

Tandem half sacks of ANFO were placed on the slope. The result was a size 2 avalanche down into our previously open terrain, almost breaking a snow gun in the runout.

That day, no other avalanches propagated down to this deep June 3rd layer.

Above: “East Face� Avalanche, 130708. Alta Chairlift is in the foreground.

Precursors Several small events occurred prior to these two avalanches, and their significance was not recognised till later.

Above: Avalanche reports for early July. Exported from MSC INFOEX.

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On the 4th of July a size 1 in Boulder Basin and a size 1.5 in Gypsy Right both ran on layers deep in the snowpack, near ground. The results at the time were thought to be isolated as the steepness, shape and fetch of the terrain were thought to be significantly different to most for the areas that had the deep 130603 layer preserved. Both these paths avalanched at a time when there were few results in other areas.

Weather The days before had been relatively normal for July. Then we had a storm on the 7th of July with gale NW winds that dropped about 30cm. Both paths have a large fetch from the NW and significant deposits built up.

Snow Structure A Melt Freeze Crust (buried 130619) existed high on all aspects. Facets rapidly developed below this pencil hard crust. These Crust / Facet sandwiches often form persistent weak layers within the Remarkables snowpack. It is probable that the avalanche in Imhoff’s Left propagated on this Crust / Facet layer and then stepped down to the 130603 Melt Form / Facet layer. There was an oblivious step in the avalanche bed surface that corresponded to this layer.

The 130603 Melt Form layer was formed when about 50mm of rain soaked the early season snowpack. The snow at the time was isolated to areas lee to the NW above about 1800m. This left a solid, knife hard layer that was only above threshold in isolated areas. Even the areas above threshold had rocks protruding through, but spaced enough to create weakness rather than anchoring. This was then buried under progressive layers, not reacting till early July.

Below: Fracture line in “Imhoff’s Left” with the obvious steps.

Photo Mark Austin

Take away Points Here in New Zealand we don’t often deal with Persistent Deep Slab. The length of time between having avalanche cycles that react on basal weaknesses meant there was little knowledge of how that would react and in what terrain.

The isolated nature of the 100603 layer and the formation of the layer before the start of the season contributed to the lack of feedback and knowledge on when and where the layer would become reactive.

The significance of precursor events was not given the weighting they deserved at the time. Hindsight is easy but more investigation of the weak layers would have been advantageous. It is however doubtful we would have picked where, when and with what trigger the Persistent Deep Slab would react.

Choosing the explosive type and size are critical but difficult with a Persistent Deep Slab problem. Obviously large shots have more effect on deeper layers. Smaller 1-2kg shots rely on touching a weak enough area of the deep layer to initiate a large enough fracture to become self propagating. This results in false feedback on its ability to be triggered. The problem is, it’s hard to identify where and when a Persistent Deep Layer has become reactive, and when to explosive test with large 10-25kg shots. Avalanches are often the first sign of a reactive Persistent Deep Slab. Persistent Deep Slab was not our primary concern at the time as we had an overnight storm cycle that produced Wind Slab. It was through testing this Wind Slab that we discovered our reactive Persistent Deep Slab problem.

When is extensive cracking over a slope good or bad? We often have small paths crack on application of explosives or ski cutting. The snow then sticks and more explosives or ski testing produces nothing. Then we have slopes that crack and next test they fall off. From my point of view the decision to open terrain is often dependent on structure and consequence. Is it a Persistent Slab? How big is the slope and how deep was the cracking? I imagine it’s something we will never have a great handle on.

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case study - june 2013 destructive avalanche cycle // brad carpenter & simon morris Brad and Simon run the snow safety programme at Porter Ski Area in Canterbury. Here is their account of the June avalanche cycle which caused structural damage, and posed challenging questions.

Between June 12-17 this year, a warm and wet weather pattern affected the north central Canterbury mountain ranges as a steady northwesterly flow pushed unseasonably warm and moist air into the region. The Porters Ski Patrol Director and I spent June 15 traversing a handful of Porters Ski Area start zones while we were still closed and observed 30-50cm of new very heavy wet snow having accumulated above 1700m. Total snowfall rapidly tapered off below 1800m. Rain fell below the 1700m elevation. The rain below 1700m decimated the existing snowpack that had fallen in May. This rain/snow line became very important in the future avalanche cycle that was to follow.

These weather observations are generally entered manually into the Mountain Safety Council INFOEX website at the individual ski areas prerogative.

Porters Ski Area has three separate remote weather stations (1350m, 1650m, 1950m respectively) equipped with wind, temp, and RH sensors with one precipitation gauge located at the base area station at 1350m. Porters Ski Area staff are able to access these sites remotely via the internet. Unfortunately on June 20, all communication with remote weather stations at Porters Ski Area was lost as the 1350m aerial was damaged by severe winds. By the morning of June 19, access to the base area was closed

The warm northwest system cleared on June 17 and a brief 36 hour period of cold high pressure ensued. This high pressure teaser was short-lived and by the evening of June 19, it had begun to snow again as a large low pressure system (dubbed affectionately as ‘the Polar Rodent’ by the TVNZ News weather commentator Jim Hickey), became centered off the east coast of the South Island and began pumping cold moisture-laden air inland from a southeasterly direction. Snow was observed to be falling at four cm/hr at 900m on the morning of June 19 and Mt Hutt closed its doors due to the severity of the storm.

Porters Ski Area officially postponed its opening to 27 June due to the severe nature of the new storm.

There is limited remote weather station information available in central Canterbury.

While a few government (NIWA) weather sites do exist, they have been placed at lower elevations and somewhat irrelevant sites with regards to mountain weather patterns.

Many Craigieburn Range ski areas operate automatic weather stations in concert with standard manual weather observations.

Right: Aerial map with overlay of the ‘Big Mama’ avalanche which over ran lift structures and the base area.

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due to heightened avalanche danger affecting our access road. All manual weather data and any hopes of repairing the damaged aerial at 1350m were effectively abandoned. By the morning of June 20, all road access from the access point at Highway 73 was closed to all public and Porters Ski Area personnel. Highway 73, the major east-west artery from Christchurch to the west coast of New Zealand, was closed to public travel around that same time.

this time observations from the central part of the Craigieburn Range did show a melt-freeze crust had formed at elevations at or above 1600m. Test results showed mostly ECTX (Mt. Cheeseman, June 21) at first on this crust with some failures with moderate energy on compression tests. General precipitation rates of three to five centimeters per hour were observed. For the duration of the five day storm, direct observations of start zones were impossible.

Storm and snowpack data information was subsequently collected via the tried and true method of picking up the phone and calling other ski field staff who were busy in their own ways trying to get their respective ski fields ready for opening. While the INFOEX was operational, all ski fields had limited access to start zones due to the heightened avalanche danger and inoperability of lifts and rope tows. At this time everyone was flying mostly blind save for what they could see at lower and mid elevations.

By the evening of June 22, the ‘Polar Rodent’ began to move away from the South Island. An estimated 1-1.5m of new snow had fallen with drifting observed up to 2-3m deep in places. Strong southeast winds had transported a majority of this new snow on to northwest aspects based on INFOEX entries, and direct observations at 900m along the Porters Ski Area access road. The decision to heli-bomb was made due to significant concerns. Firstly, because of the avalanche danger posed to the operational ski area but secondly because the access road to the base area (an 8km stretch of steep sided access road from about 700m to 1350m,) had been deemed safe only for road crews to clear below 900m at that point.

Most INFOEX observations were reporting large settlements and cracking at mid elevations with storm totals having become greatly wind affected. Around

Above: View of ‘Big Mama’ avalanche from the acces road 24hours after the event. Photo: Brad Carpenter

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At 0800 hours on June 23 a team of three bombardiers and the pilot took off from our staging area at 950m (Longspur). When we landed again two hours later we had triggered a size four avalanche on an NNE aspect, a size 3.5 avalanche on a NNE aspect, and a size 2.5 on a SE aspect with explosives. In addition we had observed natural avalanches to have occurred from size 2 to size 4. These naturals included north, west and east aspects.

office and ticket office at the southern end of the base area.

The main tongue of the debris tracked a few dozen meters uphill at the northern end of the base area, banked to the right and downhill, and channeled into the main drainage below the base area. The debris struck the edge of the snowmaking pond at 1275m shattering the ice covering on it, and pushed a six ton generator over and downhill about 50m.

The size 3.5, (HSAER3D4 – Hard Slab, Hand thrown explosive, Relative to path size 3, Destructive size 4) avalanche occurred in the avalanche path of Big Mama. Big Mama is on a northeast aspect at approximately 1950m with five numbered start zones. Start zones 1 and 2 are the most common producers of large avalanches on Big Mama, and due to their northeast aspect and concave shape, act like a catcher’s mitt for southeasterly storm events like the one we were subjected to. The Big Mama avalanche had an average crown height of 67cm and the involved slab had an average density of 252 kg/m3 as measured at a relevant test site post event on June 23. The avalanche involved an estimated area of 199,093 m2. The estimated mass was 33,715 tonnes.

The debris channeled into the creek bed and carried on an additional few hundred meters more before finally coming to a halt approximately 1677m from the crown wall. This was a total vertical distance of around 900m. Needless to say a very impressive powder cloud filled the valley below the base area. Subsequent extensive explosive testing on similar aspects, and similar elevations produced no further avalanches that day.

The main body and airblast of the slide, as witnessed from the helicopter, travelled across the base area of Porters Ski Area striking three lifts: a magic carpet, a tee-bar, and a poma lift respectively. The debris fanned out in the base area and overcame several previously bulldozed and reinforced avalanche mounds. Avalanche debris struck the corner of the base area buildings that house the operations

Simon Morris, Luke Armstrong and I were dropped at the ridge (1950m) by the helicopter following the explosive testing of the ski hill. The team moved via ridge-line onto northeast aspects of Porters Ski Area and collected data from a profile on a similar start zone to Big Mama prior to conducting a crown profile on the Big Mama avalanche itself. Both profiles isolated the reactive weak layer as the four cm thick June 19 melt freeze crust found at variable depths below the new windslab/storm slab formed between June 19 and June 23. A thin layer of very small (0.5mm) faceting round grains was found just below this crust. The weak layer was the frozen surface of the storm snow from the June 14-17 northwest warming event. The

Above: View of the ‘Big Mama’ avalanche event from the base area Photo: Luke Armstrong

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crust failed consistently with easy and moderate energy showing sudden collapse and Q1-2 results in multiple tests.

The crown line of Big Mama was observed to be on average 60-70cm thick but with a lot of variability over its length.

Some areas of the crown line were as thick as 1-1.5m and some areas as thin as 10-20cm. The crown extended an estimated 386m long with a maximum width of 330m.

The team exited the Big Mama slide path and carried on to lower elevation start zones that overhang the 2km of access road from 950m to 1350m. Extensive probing for the duration of the field work began to determine the exact elevation where the melt freeze crust existed and did not exist. This began to make clearer the conundrum of why test shots on similar aspects, but lower elevations had no results. But the nagging question was, why had areas of similar aspect and elevation not produced avalanches?

The next several days thankfully saw a strong high pressure system dominate the South Island. At Porters Ski Area a unique snow safety operation was implemented. Access to start zones remained limited as groomers were needed to reduce the avalanche debris in the base area so that repairs could begin. Safety operations consisted of approaching upper start zones on touring skis with all the accoutrements relative to a backcountry trip in the mountains, together with explosives. Prior to our entry into any start zones we would call off all workers and contractors in the base area and they would proceed to designated safe areas. Explosive testing was conducted if needed, and what I came to think of as “guerrilla data gathering” would generally take less than an hour. Most times this consisted of digging several test profiles, and quickly moving out of start zones to limit the amount of downtime, and ultimately costs due to downtime in the base area.

The weather continued to be cooperative to our efforts but this was a double-edged sword. On the one side we had no new danger to consider as no new snow or wind had occurred, but on the other side it meant that the weak layer we were dealing with wasn’t going anywhere.

Another series of test profiles in zones No. 3, No. 4, and No. 5 of Big Mama (the zones that hadn’t avalanched yet) showed several startling ECTV SP results in thin areas and we continued to see ECTP with moderate energy in thicker areas. It seemed like things were certainly not getting any better and were possibly getting worse. By this time, through our field observations and other INFOEX entries, it was accepted that the weak layer was isolated to elevations above 1680m.

So the big concern was any new load from future storms.

Would future loading set us right back to the same place as we were on June 23? Is it possible to do anything to this weak layer in the meantime? Puzzling over the conundrum, as rebuild and cleanup efforts continued, led me to the “Systematic Application of Explosives” (SAE) work conducted at Aspen Highlands, Colorado, USA. When in doubt blow it out, although at Aspen Highlands the SAE work is generally to prevent future avalanches. On June 27, we applied 25 individual 1kg Powergel explosive rounds to the No.3, No. 4 and No. 5 start zones of Big Mama. No avalanches occurred. By the next day a significant warming event had effectively broken down many areas where the June 19 crust had existed. A robust solid melt freeze/ice crust was formed at the surface on July 4. This new crust was aptly named the Freedom Crust.

The avalanche cycle in the Craigieburn Range, and the Mt Hutt Range was one of the most prolific, widespread and destructive avalanche cycles in recorded history in the north central Canterbury mountains. The speed and subsequent reactivity to which the June 19 melt-freeze crust had formed, had started to facet just below, and had reacted to a new load was remarkable in its own right. The strange thing was why were major avalanches recorded at three ski fields located just a few kilometers south and east of other ski fields north and west that had triggered no major avalanches? In multiple backcountry trips over the next few weeks I was able to document several other large avalanches that had occurred throughout the Craigieburn Range on all aspects. These avalanches all had the same characteristics as those observed at Porters Ski Area and other ski areas including Mt. Hutt and Mt. Olympus. There were no other major storm events during the time period following the early June events so these other avalanches had to have occurred naturally during that storm. I continue to ponder just why the avalanche activity was essentially isolated to the southern areas of the Craigieburn Range. If anything, the widespread, large avalanche cycle that was isolated to portions of the Canterbury region reinforces the ephemeral notions of human forecasting and natural hazards...sometimes there is no logical, scientific answer, and that’s what keeps me in this business.

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PARTING PICs

Above: Powder ghost -proof from the Southern Lakes region that there was good snow to be had. Photo Chris Cochrane Below: Visiting guide Nico ( Mt Aspiring Guides) enjoys a day tour to Black Peak, Photo: Gordie Smith

NEXT ISSUE OF

CRYSTAL BALL

DUE: 10 June 2014

Submissions deadline due:

6 MAY 2014

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