Geography Reference
In-Depth Information
are very disruptive to road and railroad traffic. Thus, on one hand, people avoid places
where destructive processes are known to occur but, on the other hand, they use the
resulting landforms and deposits for construction and agricultural purposes. While the
primary cause of slope instability is the gravitational pull, inherent and prior conditions
favoring movement and a trigger to set off movement are necessary. Such conditions
include weathering of earth materials, a build-up of gravitational stress due to added
material and water, and a reduction in slope stability and strength due to undercutting
by erosion and construction and the addition of water to the material. Triggers include
earthquakes, volcanic eruptions, sudden and intense rainfall, freezing and thawing tem-
peratures, and construction activities. While slope instabilities of all types are endemic
to mountain topography, it is clear that human alteration of slopes has increased their
distribution, frequency, and magnitude. This is especially evident where deforestation
and road building take place (Petley et al. 2007; Sidle et al. 2011; Fig. 10.19).
FIGURE 10.20
Snow avalanche prevention, control, and mitigation adaptations. (A) traditional sum-
mer pasture shelters built into an avalanche slope, Kaghan, Punjab Himalaya, Pakistan. (B) ava-
lanche deflecting walls at La Lavanche. (C) snowpack stabilizers at La Tour, Haute-Savoie Alps,
France. (Photos by J.S. Gardner)
The hazards of slope instability have been recognized through experience for gener-
ations. Modern research is adding to the body of knowledge. While some human activ-
ities and unfortunate locational decisions continue to exacerbate hazard and risk, a
wide range of mitigative efforts are now in place in many mountain regions to reduce
both. Avoidance of areas prone to or threatening slope instability is a traditional and
most effective approach undertaken by free choice and/or regulation and restriction,
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