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The Role of Avalanche Character in Public Avalanche Safety Products

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The Role of Avalanche Character in Public Avalanche Safety Products THE ROLE OF AVALANCHE CHARACTER IN PUBLIC AVALANCHE SAFETY PRODUCTS Karl Klassen* Canadian Avalanche Centre, Revelstoke, British Columbia, Canada Pascal Haegeli Avisualanche Consulting & Simon Fraser University, Vancouver, British Columbia, Canada Grant Statham Parks Canada, Banff, Alberta, Canada ABSTRACT: Avalanche character is a significant factor in professional decision-making (Atkins, 2004). Weak layer/interface, slab properties, persistence, weak layer location, propagation propensity, and rela- tive size (Statham et al., 2010) play an important role in how risk management decisions, such as terrain selection and timing, are implemented in the field. In recent years, avalanche character has become an essential component of Canadian public avalanche forecasts, along with its inclusion in standardized rec- reational avalanche training curricula, and in decision making tools such as the Avaluator V2.0 (Haegeli, 2010) and the Decision Making in Avalanche Terrain Fieldbook (Haegeli, Atkins & Klassen, 2010a). This paper reviews the current avalanche character definitions and suggests improvements and refine- ments. Current usage is reviewed and potential new applications are explored. Recommendations are provided for public avalanche safety agencies that do not currently use avalanche character but who are considering incorporating avalanche character into their products or services. 1. INTRODUCTION cept developed by Atkins (2004) was used as the foundation for the Avalanche Danger Scale revi- In his seminal paper at the ISSW in 2004, sion project, which developed the Conceptual Roger Atkins proposed that professional heli- Model of Avalanche Hazard (Figure 1) after exten- skiing guides’ perception of risk is strongly influ- sive and exhaustive efforts by an international enced by the characteristics of expected ava- committee. Avalanche character was a key com- lanches regardless of the present stability ratings ponent of this model and a matrix was created (Atkins, 2004). Atkins presented a list of 27 ava- (Table 1) that defined the key characteristics of lanche scenarios (e.g., widespread wind slabs, various kinds of avalanche (Statham et al., 2010). mid-sized slab avalanches in storm snow) and discussed a distinct risk mitigation approach for each of these scenarios. He concluded that the description of the character of the current ava- lanche scenario is crucial for effective communica- tion of avalanche hazard, both among avalanche professionals and in public avalanche safety prod- ucts. At the same time, similar thoughts were ex- plored by the Swiss guiding community. Wasser- man and Wicky (2003) highlighted the importance of recognizing the present avalanche scenario in choosing the right risk mitigation strategy and Har- Figure 1: Conceptual Model of Avalanche Hazard et al. vey (2008) introduced four distinct avalanche (Statham , 2010) problems: New snow, old snow, wet snow and wind driven snow. Soon after, avalanche character and the con- Back in North America, the preliminary con- ceptual model were adopted by the Canadian Ava- lanche Centre (CAC) as fundamental components of the forecasting of avalanche hazard and com- * Corresponding author address: munication of danger to the public. Avalanche Karl Klassen, Canadian Avalanche Centre, Box character was added to the CAC’s recreational 2759, Revelstoke, BC, Canada, V0E 2S3; Avalanche Skills Training (AST) course curriculum tel: 250-814-8981; fax: 866-366-2094; for the winter of 2010-11 and included in support- email: [email protected] 493 ing decision aids such as the Avaluator V2.0 Wet Slabs (Haegeli, 2010) and the Decision Making in Ava- Persistent Slabs lanche Terrain Fieldbook (Haegeli, Atkins & Klas- sen, 2010a). Deep Persistent Slabs Avalanche character has also been adopted Cornices by numerous other agencies including Parks Can- Each category is defined according to weak layer ada and Kananaskis Country in Canada as well as or failure interface, slab properties, persistence, the Utah Avalanche Centre (UAC) and the Colora- weak layer location, propagation potential and rel- do Avalanche Information Centre (CAIC) in the ative size potential. United States, and it has become a central com- The CAC expanded on the matrix by develop- ponent of avalanche danger communication in ing a series of “Avalanche Problem Essentials” North America. papers (Haegeli, Atkins & Klassen, 2010b) aimed at recreationists. These papers describe the de- 2. DEFINITIONS velopment, associated avalanche activity pattern, tips on recognition and assessment in the field and The Danger Scale project’s avalanche charac- risk management strategies for each of the eight ter matrix (Statham et al.,2010; Table 1), divides avalanche character types. These expanded de- avalanches into eight categories: scriptions provide the basis for teaching users Loose Dry about avalanche character and its role in decision Loose Wet making, thus assisting users of CAC forecasts in making informed decisions about hazard and risk Wind Slabs mitigation. Storm Slabs Table 1: Avalanche Character Matrix (Statham et al., 2010) Character Weak Layer/ Slab Properties Persistence Weak Layer Propagation Relative Size Interface Location Potential Potential Loose Dry Various (no None Hours/days Near the sur- Down slope R1-2 cohesion) face entrainment Loose Wet Various (no None Hours/days Any level Significant R1-3 cohesion) down slope entrainment Wind Slabs DF, PP 4F-K Hours/days Upper pack Terrain feature R1-3 Wind transp. Storm Slabs PP, DF F-P Hours/days In or just below Path R1-4 Soft-stiff storm snow Wet Slabs Various 4F-P Hours/days Mid pack ot Path R1-5 (climax) Wet grains deep Persistent Slabs PWLs such as 4F-P Weeks/months Upper to mid Path to adja- R2-4 SH, FC, CR, Stiff-hard pack cent paths FC/CR combo Deep Persis- PWLs such as 1F-K Weeks/months Deep or basal Path to adja- R1-5 (climax) tent Slabs SH, FC, CR, Hard cent paths FC/CR combo Cornices ~ ~ Months w/ ~ ~ ~ short peaks Comment Typical failure Typical kind of Typical dura- Relative to HS Typical expec- Typical range plane slab tion of instabil- tation of size relative ity to path 494 Figure 2: Avalanche Problem Guidance for Backcountry Forecasters (Greene & Lazar, 2012) The matrix and the CAC’s expanded defini- A brief information statement. tions also provide internal guidance to forecasters Travel and terrain advice, which describes who must assess which avalanche character travel techniques and terrain choices that help should be used to describe the current problem(s) mitigate risk. in a given forecast. Other jurisdictions have used the original ma- Chunking the Avalanche Problem and using trix and the CAC’s work to develop internal and avalanche character as part of the description of external guidance statements. Notably, the CAIC the problem significantly enhances avalanche has developed a quick reference flow chart for forecasts by making it simple for the user to un- their avalanche forecasters (Figure 2; Greene & derstand not only what the regional danger rating Lazar, 2012). is but what kind of terrain choices and techniques might be employed to manage risk. Much like professionals, who adjust their ter- 3. AVALANCHE CHARACTER IN PUBLIC rain and risk mitigation techniques according to SAFETY INFORMATION IN CANADA avalanche character regardless of other factors In recent years, the public avalanche forecasts such as snow stability ratings (Atkins, 2004), rec- in Canada have become increasingly “chunked,” reationists also need to take the character of the meaning information is broken down into shorter, existing avalanche problem into account when simpler statements that incorporate graphical ele- making terrain choices under a given danger rat- ments to provide to-the-point information in a ing. standardized format. Avalanche character fits For example: a Considerable danger rating squarely into the “Avalanche Problem” chunk of could be applied when many small Wind Slabs are information (Figure 3), which describes: expected to run only to terrain transitions. At the same time, a Considerable danger rating could What kind of avalanche is expected. also be applied when infrequent but large, Deep Where the problem exists. Persistent Slabs will likely to run to valley bottom. The likelihood of triggering. In these two scenarios however, even though the danger rating is the same, completely different How large an avalanche is expected. terrain choices and travel techniques will be 495 Figure 3: CAC Avalanche problem information chunk, created using the AvalX forecasting software (Stat- ham et al., 2012) required to manage risk. However, despite these and Recording Standards (OGRS) of the Cana- efforts, our experience shows that the concept of dian Avalanche Association (CAA, 2007) to dif- adjusting terrain choices or travel techniques ferentiate between slab and loose avalanches. according to avalanche character is currently not We believe that avalanche character is simply well understood or practiced in the recreational an extension of the existing avalanche type defi- community nition and that the two concepts should be com- bined in the next revision of ORGS, at which 4. CHALLENGES AND SUGGESTIONS point the term avalanche type should replace avalanche character as the term of choice. Based on our experience, we have identified We propose using the term “Avalanche Type” as a number of challenges for the application of the concept of avalanche character in public ava- the label for avalanche character, and that ava- lanche
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