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Show THE FOREST SERVICE AVALANCHE HANDBOOK Part I History INTRODUCTION Since the preparation of " The Alta Avalanche Studies" in 1948 continued progress has been made in the observation of snow and avalanche phenomena in the United States. The " Avalanche Handbook" replaces the " Studies" on the basis of four additional years of observation at Alta in Utah, plus two years at Berthoud Pass in Colorado, two at Mt. Baker in Washington and one year at Stevens Pass in Washington. Thus our snow and avalanche information has more than doubled in volume and the base of observation has widened to include all the climatic variations of the western United States, The " Studies" did not pretend to be definitive. It was an attempt to gather together all the relevant information we had. It was also a progress report derived from a number of years of systematic investigation. The purpose was to set up principles and techniques for the use of administrators in the field. In particular the " Studies" dealt with ten avalanche factors which had been identified, recorded, analyzed and reduced to a set of guides by which the man in the field could estimate avalanche hazard and take appropriate action. These guides or " rules of thumb" have stood up well under the test of three unusually severe winters. At the same time experience has caused modification of some earlier ideas. Research in new directions has refined the process of hazard forecasting while constant experimentation has improved our techniques of reducing that hazard. When the " Studies" was written, avalanche control, or snow stabilization through the use of hand- placed explosive charges and projectiles was hardly beyond the experimental stage in this country. These are now standard techniques, widely employed. During the winter of 1950-' 51 at Alta we fought what amounted to a pitched battle, artillery versus avalanches. The snow rangers won. " The Alta Avalanche Studies" was widely distributed as the only comprehensive work of its kind in this country. It became the basis of snow safety programs far from the source. If nothing else, the four years since its publication have disposed of the argument that because the " Studies" was derived from one location its value was limited to that area. Our basic contention has been proved: that wherever it falls snow is snow and behaves in a characteristic manner. We recognized, of course, that there are avalanche combinations outside the normal experience of Alta and for which our information was either deficient or lacking. In 1949, Andre Roch, internationally famous - 1 - |