文档介绍：
253-1 5
1 . Avalanche releases typically result
from natural occurrences, such as
heavy snowfall or melting condi-
tions, or from human activity, such
as skiers or hikers crossing a start-
ing zone.
2. Slab avalanches occur when a layer
of cohesive snow fractures as a
continuous unit and slides down
the slope. These are by far the
most dangerous type of avalanche
due to the large volume of snow
that can be released and the large
area that can be affected .
3 . plex temperature and
structural changes in a snow mass
make it difficult to predict
avalanches . However, it ispossible
to map high-risk areas because
HOUSES MOVED BY WET SNOW AVALANCHES avalanches tend to ur in the
same locations .
OUTER LIMIT ZONE I :IMPACT PRE55URE > 615 PSF BASED ON VOELLMY'5 EQUATION
4. Avoidance of known avalanche
---- -OUTER LIMIT OF AVALANCHE DEBRIS ASSIGNED TO ZONE 1 hazard areas is the best way to pre-
vent damage . A number -
- ----- - ESTIMATED RUN-OUT OF 1973 WET SPRING AVALANCHE
munities have developed regula- N
restrict development in
. . . . . . . . . . . .. OUTER LIMIT OF ESTIMATED WET SPRING AVALANCHE THAT MOVED HOU5E5 1 AND 2 tions to
hazard areas. u
ZONE II : IMPACT PRESSURES < 615 PSF BASED ON VOELLMY'S EQUATION. 5. Hazards can be reduced by artifi- c
cially triggering small avalanches to
OUTER LIMIT OF WET SPRING AVALANCHES FROM SIDES OF ADJACENT VALLEY, CLA561FIED
? prevent snow buildup, or -
t A5 WITHIN ZONE I.
paction of the starting zone snow
to stabilize the slope. â
Figure 253-18. Mapping of avalanche microzonation . O
6. Structural avalanche control strate- C
gies include the anchoring or redis-
tribution of the snow pack, or the
structural protection of people and N
property (Figures 253-19 and 253- N
20) . Many methods are costly and
should only be considered as a last N
resort.
I
L
ar
cd
Z
Figure 253-19 . Avalanche control structures. A number of different