Hazard Zoning in Areas with Major Deep-Seated Landslides: Case Study from Switzerland
TOBLER D., KEUSEN H.R. (2013)
Margottini, Canuti, Sassa (Eds.) Landslide Science and Practice, Vol 1, pp 337-343, Springer
The large, deep-seated Gryfenbach landslide in Lauterbrunnen, Switzerland, endangers part of the village as well as the main entrance to the whole valley. A mass of about 25 million m3 is situated at the left valley entrance and moves with an average of cm a year. In the steep frontal part of the sliding mass two large spontaneous landslides have been recorded (secondary processes). Following the abnormally intensive snowmelt in spring 1999 the movement increased thirtyfold. Important infra-structures within the landslide were destroyed. A complicated monitoring system has been installed to under-stand the landslide’s behaviour and hazard potential in detail.
At the same time the authorities start to elaborate the hazard map of the valley. Through extensive field investigations, analyses of monitoring data and conclusions by analogy from other large landslides the relevant scenarios for the hazard assessment have been formulated. In 2003 the first draft of the hazard map existed (GE-OTEST AG, 2003, see Figure 10). In 2011 a revised hazard map has been published (GEOTEST AG, 2011). This product is based on today’s hazard assessment methods. The paper focuses on the Swiss hazard assessment methodology, on the scenario definition of large, deep-seated land-slides illustrated on the case study in the Lauterbrunnen valley.