OCR Text |
Show 13 Dry snow jetted to the lee of the standard jet roofs on Bridger Ridge does not accumulate in localized drifts. Snow depths 20 to 30 m to lee of these structures were no different during normal dry snow conditions than in adjacent areas where no jet roofs were emplaced. In the case of wet snows, however, considerable drifting was observed. Snow jetted from cornices by jet roofs can be caught by downwind snow fences, and thus may be utilized to increase the water storage potential at high elevations. It should be noted, however, that such snow fences would have to withstand the standard creep stress of deep snow which amounts to several thousand Kg/ m on 30 slopes. EFFECT OF RIDGELINE TREES Distorted low pine and alpine fir along Bridger Ridge have varying effects on cornice accretion along the ridge. Early season lee drifts form adjacent to such trees, but cornice projection is minimized until snow covers the trees after which it can be saltated or rolled up to the ridgeline without disturbance. The cornices formed to the lee of trees are thus usually smaller than cornices formed in adjacent areas where no trees exist. It can be stated, therefore, that trees are somewhat beneficial in preventing cornices, but not totally so. SNOW FENCING AS A CORNICE PREVENTATIVE Current experiments with snow fences are under way. An objective is to cause premature drifting to the lee of upwind snow fences, thus " spoiling" the airflow regime necessary for cornice formation. If this is effective, it would provide an economical method of cornice control. A. Roch ( pers. comm. 1967) has also suggested that a type of " reverse" jet roof, inclined upwind, would possibly have the same effect; that is it would spoil the airflow conditions necessary for cornice formation |