Geography Reference
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1724 and 2002, showing that rockfall activity has increased over the last century, pre-
sumably because of warmer temperatures, not annual or seasonal precipitation totals,
and peaks during the early spring when trees are dormant (Perret et al. 2006).
FIGURE 5.13 Evidence of rockfall events occurring in the Gore Range, Colorado. (Photo by J. R.
Janke.)
The geomorphic significance of rockfall lies in its ability to rapidly and powerfully
transport material. The largest recorded rockfall and associated slide involved over 10
km 3 of mass along a fault plane in central Nepal (Heuberger et al. 1984). Falling rocks
move at high speeds and can cause considerable damage on impact, whether they strike
another rock, a tree, or simply the ground. Of course, falling rocks are very dangerous
for people; this is why protective structures are often built next to mountain highways
passing through rugged terrain, or large sections of netting are draped over critical sec-
tions of steep walls. Most of the time, however, highway travelers must settle for a sign
warning about “Falling Rock.”
Geospatial technology has been used to better understand rockfall characteristics
and hazards. Abellan et al. (2006) used terrestrial laser scanning to determine rockfall
trajectories and velocities as well as calculate the geometry and volume of the source
area. Krautblatter and Dikau (2007) suggested that the complexity of rockfall modeling
could be reduced by separating a hillslope into the stages of back weathering, filling and
depletion of storage on the rock face, and finally rockfall supply onto the talus slope.
A GIS software program, RockFall Analyst, allows computation of 3D trajectories,
spatial frequency, flying/bouncing height, and kinetic energy of falling rocks (Lan et al.
2007).
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