Predicting the hazards
Figure 1. A typical hazard map used by the local authorities in the Wallis region of Switzerland. Land is divided into red and blue zones based on the expected impact pressures of an avalanche with a return period of 300 years. The grey region shows the extent of the avalanche debris following a large snow slide in 1999. Snow and ice covered the road and came within 200 metres of the railway line. The map performed well because the avalanche debris was confined to the blue region. (Picture credit: Swiss Federal Office of Topography)