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Avalanche Handbook

Avalanche Handbook. David McClung and Peter Shaerer. Second Edition. The

Mountaineers, Seattle, Washington, 1993. 272 pages, photos and drawings.

Soft cover. $19.95.

“I only hope that the snowpacks will understand that I have read these chapters and will spare me from the avalanche”

At last we have a major revision to The Avalanche Handbook, not written this time by the US Forest Service, but by Canadian authors. After four years of no handbook (out of print), David McClung and Peter Shaerer came up with a revision that will be the textbook for avalanche courses perhaps for decades to come. This new handbook is a very comprehensive treatment of the subject, following in the tradition of the earlier handbooks (the USFS Handbook #194 by LaChapelle, 1961 and the USFS Handbook #489 by Perla and Martinelli, 1976).

First of all, as field avalanche people we view the new Avalanche Handbook as a logical development from the previous versions and in many ways a much needed improvement, updated with some of the latest information. It has better layout and design. The cited literature is current. It does a good job discussing and emphasizing snowpack tests: such as the hand hardness test, the Rutsch- block, and the shovel shear test. (However, it would have been better to mention that since the Rutschblock must be done on a slope of at least 25° to be effective, whereas the shovel shear can be meaningful even on level ground, the shovel shear is a potentially safer test to perform.) Since the authors are engineers and geophysicists they do an especially good job when discussing engineering problems such as guidelines for design in the run-out zone. The Canadians finally set the record straight on avalanche size and classification. The USFS system for sizing avalanches was illogical and ignored by field people.

The book has a Canadian accent and uses the metric system with no exceptions. This will be a problem for those in the USA who still measure snow in inches and temperature in degrees Fahrenheit. Some may find the text rather textbook-like. The authors tried to liven things up with well-chosen quotes at the head of each chapter. Misprints are few, although on page 64, figure 4.5, there is a reversal of the top arrow on the tension illustration.

This new handbook is not as current as it could be. It has not kept up with technology in Little Cottonwood Canyon (Alta, Snowbird, UDOT), Utah, the site that heavily influenced the earlier handbooks. Visitation in the Canyon has increased many fold, and Canyon personnel have responded with innovative safety logistics supported by new forecasting, control and communication procedures. The other front lines that are not covered are the avalanche warning centers and their technology and forecasting systems (i.e. Utah Avalanche Forecast Center, Northwest Avalanche Forecast Center, Colorado Center), and most important, technologies and forecasting at heliski operations, which are certainly significant in the larger view, especially in British Columbia, the authors’ home base.

Chapter 3 presents snow metamorphism in non-technical terms with up-to-date concepts. Appendix C “Advanced Snow Crystal Classification Systems” is of particular value to the avalanche worker. However, for the terms used to describe the metamorphic processes in dry snow, McClung opted not to use the terminology used by the International Commission on Snow and Ice (of which McClung is a member) and uses the terminology common in Canada. As a result, we again have a change in terminology to describe the evolution of snow on the ground to depth hoar as the Temperature Gradient Process (TG), to Kinetic Growth Form, and McClung’s preferred Faceted Forms. All these mean the same thing, whether the process takes place north or south of the Canadian border.

The three classes of “stability factors” presented in Chapter 6 are interesting. Unfortunately the very close interrelatedness of the three factors seems to be only indirectly stressed. This interrelatedness, rather than any one factor, is fundamental to both stability evaluation and forecasting. A more misleading suggestion is that Class II Snowpack Factors are superior to Class III Meteorological Factors (because Class II Factors involve less random data, presumably). In fact, a snowpit (a leading Class II data gathering technique) is only one hole (or two) on an expanse of slope to say nothing of a whole mountain range. Snowpit data by itself is limited and more than one ski guide has released deadly avalanches during or after digging a snowpit. To suggest the Class III Factors are less important than the Class II Factors could be misleading (page 126, right column, “Which Observations Have Priority”). At any one time, any given “Factor” may be the all-important one, or all of them, which is often the case. In fairness, a reader reading the entire handbook will realize the authors intend the concept of “Factor” interrelatedness to be implicit.

In Chapter 7, avalanche prediction will certainly be of interest to most people who use this book. The discussion of the traditional ten contributory factors (with the worthwhile addition of relative humidity and solar radiation) is well-done and concise. However, it seems the authors don’t have much to say about putting them all together in an organized forecasting system using storm plots and forecast graphs, as are in use from Little Cottonwood Canyon to Rogers Pass to the Canadian heliski operations. In fact, “conventional forecasting” seems to be dismissed in a very short section indeed (page 164); the future apparently being with numerical or expert systems computer programs. The fact is that nobody has been able to make these programs work. Consequently forecasters, guides and backcountry skiers/mountaineers with skill for abstract reasoning capabilities and common sense are still in demand.

In summary, we feel that the authors are showing their science-engineering training bias when it comes to dealing with the more abstract subjects of stability evaluation and forecasting. At the same time this background adds strength to many of the other chapters. All in all it is a good job, one that needed to be done, so just taking it on is highly commendable.

A final note. There has been only one permanent and essential contributor to both the 1976 USFS handbook and this 1993 McClung and Shaerer handbook; Alexis Kelner, the illustrator. McClung and Shaerer have used and copyrighted 72 illustrations and 12 photos originally prepared in 1976 almost as a labor of love by Alexis Kelner. In many respects, Kelner’s illustrations remain the strongest and most lasting contribution to the handbook preparation.

Tom Kimbrogh, Peter Lev and Ron Perla