Because of their sudden and (in many cases) unpredictable nature, fall events can be very dangerous for the infrastructures and the population.
Damages extent depends on energy of the falling material (function of weight and velocity). Rock falls can damage housing, interrupt roadway systems and cause human losses.
Fig. 9: Car damaged by a rock fall at Upper Island Cove, Canada, on February 14 1999. A 8 ton block toppled from the top of a 100 m slope, ran roughly 150 m, struck a house, and landed on the top of a car parked beside the house (from www.heritage.nf.ca)
Constructive layouts exist to protect housing, such as reinforcement of the exposed façade or the roof. But the best way is to avoid building in vulnerable areas and to use protection techniques.
Consequences of the rockfall avalanche process
Rock fall avalanches are incredibly destructive, they move with great rapidity and obliterate everything in their path. Perhaps the most important, once an event has occurred, is to discover whether the avalanche has dammed the valley. If it has, and a lake has formed, maximum effort must be given to take control of the breaching dam, because the resulting flow may cause a second disaster.
Consequences of the topple process
Topples are potentially very dangerous because they develop at first by loading, then by progressive basal failure and rotation, and eventually sudden collapse. This failure is dramatic, the break-up spectacular and the velocity of loose boulders and run-out high.
Damages on the infrastructures and population are the same than concerning fall risk (see details on fall).
References:
BESSON L., 2005. Les risques naturels: de la connaissance pratique à la gestion administrative. Editions Techni. Cités, Voiron, 60 p.
LEONE F., ASTE JP., LEROI E., 1996. Vulnerability assessment of elements exposed to mass movements: working toward a better risk perception. In: Senesset K (Ed): Landslides, Proceedings of the 7th International Symposium on landslides, Balkema, Rotterdam
Websites:
www.irma-grenoble.com
www.prim.net
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