Early warning systems related to mountain hazards

Hans Kienholz
International Association of Geomorphology, Mountain Hazards Project, Geographical Institute, University of Bern, Hallerstraße 12, 3012 Bern, Switzerland.
Tel. : +41-31-6 31 88 84 or 6 31 88 59, Fax: +41-31-6 31 85 11

Mountain hazards, such as snow avalanches, rockfall, landslides, debris flows, and torrential processes are responsible for disasters and catastrophes in mountainous areas every year. In many of these densely populated areas governmental agencies or the inhabitants themselves try to protect settlements and traffic routes by active measures (for example checkdams, etc.) and/or passive measures (for example hazard zoning, planning of evacuation, closing of railways and roads in case of acute danger, etc.). All these measures, especially the passive ones require early warning. Early warning can concern either (1) the basic disposition of an area for dangerous processes (e.g. long-term preconditions, such as the general instability of a slope), or (2) the variable disposition (e.g. short-term state of the snow cover on an avalanche slope), or (3) the immediate effect of triggering events (e.g. thunderstorms triggering flash floods). There is a wide span of technical realisations of early warning systems for these three phases. In many cases traditional warning by attentive observers is the most adequate solution; in other cases sophisticated electronic devices provide better safety.

In all cases however, it is essential that early warning systems are very well applied by the involved experts, by the regional and local authorities, and by the population. The best concepts and the most sophisticated instrumentation are useless if the alert is not transmitted to the menaced people at the right time and if no accurate planning of emergency measures is provided.