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Show THE NATURE AND CONTROL OF SNOW CORNICES ON THE BRIDGER RANGE SOUTHWESTERN MONTANA INTRODUCTION Prevailing westerly winds create large snow Dornioes ' along the lee crest of the Bridger Range in Southwestern Montana, Studies during the winters of 1965- 68 revealed some of the mechanics of cornice accumulation and deformation and showed that cornices may be controlled by wind deflecting structures. The study site averages 85OO ft. ( 2590 m.) A. S. L. and extends a linear distance of one half mile ( 0.8km.) at the head of the Maynard Creek watershed. Prevailing winds are from the west, or approximately perpendicular to the Bridger ridgeline. Maximum wind speeds occasionally exceed 100 mph ( 44.7 mps). Since a high proportion of naturally triggered avalanches in many recreation areas are caused by cornice collapse, prevention or control of these features is of importance where recreational safety is of primary importance. To a large extent, this paper is an embellishment of the excellent pioneer writings of Welzenbach ( 1930), and Seligman ( 1936). and the unwritten ideas of that master mountaineer, Andre Roch. DEFINITION For purposes of clarity, a cornice ( German " Wachte") is defined as a projection of snow formed by wind deposition to the lee of a ridgeline or slope inflection. A typical composite cornice is illustrated in Fig. 1. STORED WATER The declivity of lee slopes controls the size of cornices developed upon them, hence the amount of water that is available from cornice snow. |