|
|
Figure 2 Natural avalanche activity along the transportation corridor throughGlacier
National Park. The avalanche activity index is the sum of all natural avalanchesconsidering
avalanche size by a weightingfactor (approximately related to thevolume).
|
Initially,artilleryavalanche controlwasunsuccessful inlikely due to depth of the weak layer.Substantial cooling
initiating release of this weakness due to the spatial distri-may also have contributed to stabilization.
bution of the surface hoar layer,andto the slab propertiesThe casestudysuggeststhatmonitoring snowpackweak-
that were not favourable forfailure initiation (Schweizernessesisan essentialpartofsuccessful stabilityevalua-
et al., 1995). Finally, during theavalanchecycle of Januarytion.Jamieson (1995) showed in detail that the skiersta-
10-11,1996,avalanches fromthe high elevationstartingbilityindexisa betterpredictorforskiertriggered slabs
zonesrunningonanewsnowinstability,triggeredthethan common meteorological observations. Consistent and
surface hoar layer in most avalanchepaths resulting in thecontinuous shear frame measurementsin a representative
release of large masses of snow.study plot on new (storm) and old (persistent) snow insta-
Skier triggeringwas unlikelyuntil about 5 January 1996.bilities is a good method tomonitorthe strength of weak
Most involvements were reported around 8 January 1996layers.Asslabpropertiesare importanttoassessfailure
after additional snow fall, and in particular, after warmingpropensity, these measurements should be complemented
quicklychanged the slab properties.Afterthe laststormwith stabilitytests on nearby slopes.
on15January1996,skiertriggering quicklybecameun-
|
|
1
2
3
