On the terminology and indexes of avalanche activity
During the long period concepts of avalanche activity and avalanche hazard in the USSR quite often substituted each other. The term avalanche risk began to use more often in the beginning of 1990s. We conduct the analysis of terms avalanche activity, avalanche hazard and avalanche risk. We offer their definitions based on general ideas of activity, hazard and risk of various natural processes. Avalanche activity is intensity of avalanche process on a separate site. Intensity is characterized by geophysical parameters of avalanche itself and spatial-temporal characteristics of avalanche action. Avalanche hazard appears when avalanche action can harm the person or environment. Therefore, avalanche hazard is the existence of threat for definite type of object in concrete terrain due to avalanche release. Such objects are follows: people, constructions and devices of a natural habitat valuable to the person. Thus, avalanche hazard takes into account not only geophysical exponents of avalanche activity, but also social and economic indices in explored terrain. The avalanche risk is the probability of losses appears due to action of avalanches, for determined time (for example, for a year). Precise definitions are necessary for unification of methods of assessment of territory, as well as techniques of avalanche maps composing, and also the name and the content of maps.