Hazard Zoning in Areas with Major Deep-Seated Landslides: Case Study from Switzerland

摘要

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 m~3 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 30-fold. Important infrastructures within the landslide were destroyed. A complicated monitoring system has been installed to understand 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of the hazard map existed GEOTEST AG (Technischer Bericht zur Gefahrenkarte Lauterbrunnen, Nr. 00063.5, Zollikofen (unpublished), 2003), see Fig. 10). In 2011 a revised hazard map has been published GEOTEST AG (Lauterbrunnen, Naturgefahren, Bericht zur Teilrevision Gefahrenkarte, Nr. 10151.01, Zollikofen (unpublished), 2011).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 landslides illustrated on the case study in the Lauterbrunnen valley.