S n o w

C o v e r

S t a b i l i t y,

A v a l a n c h e

I n i t ia t i o n

a n d

F o r e c a s t i n g

of the column sides and hence the advantage of keeping
columns a consistent size.(The three decreases apparent
at 35 x 35cmall occurred late on 9 March 1996when it
began to drizzle.)
Duringthese trials,operatorswere encouraged tore-
port subjective preferencesconcerning column size. Their
preferencewasfor 30 x 30 cm columns except for onelayer
which seemed to produce "cleaner" shears for 25 x 25 cm
columns.Overall,the 30 x 30cmcolumn size specified
by the CAA(1995) appears well chosen.

EFFECT OF SHOVEL SIZE AND SHAPE

To assess the effect of shovel design, tests with a relatively
flat metal blade were alternatedwith tests using a smaller
curved plasticbladeon14 March 1996.The weaklayer
consisted of 0.3-0.5 mm faceted crystals 24 cmbelow the
surface.A Wilcoxontestwas used to compare the com-
pressionscoresfromadjacenttestswiththedifferent
blades (Table 5).Foroperator4,the difference in scores
fromthetwoshovelbladesismarginallysignificant
(p= 0.09).Foroperator 5 and when both sets of alternat

CompressionScores

for

Varying-Size

Columns

Cariboos,Monashees

andPurcells,Winter1996

30

Hard

20

Mod

10

Easy
0
2025303540

LengthofSidesforSquareColumn(cm)

Figure 5 Effect of columnsize on compression scores

78