In March of 1999, melting snow cover combined with heavy rainfalls in the northeastern part of Switzerland resulted in the occurrence of numerous shallow landslides. This diploma thesis project involves the investigation of one such slide and the surrounding area; notable because of the geological factors contributing to the slide and the large number of preserved features characteristic of shallow sliding masses.

Located in subalpine Molasse of northeastern Switzerland, 2 km east of the town of Rufi in the Lithebene (Canton St. Gallen), the slide involved the mass movement of surficial soils and a conglomerate rock unit with a maximum displacement of approximately 100 m. The shear surface appears to coincide with a smooth marl surface and signs that the slope was heavily saturated are still present. Damage relating to the slide includes the destruction of a paved single-lane road and approximately one square kilometer of forested and pastured land. Given the apparent conditions contributing to the slope failure, similar slides within the region are highly probable.

Based on this preliminary assessment, the objectives of the diploma study are as follows:

• to map in detail the geology and structure of the slide mass and the surrounding region;
• to map and characterize small-scale displacement indicators (i.e. compressional, dilational and transform strain features), which may then be used as quantitative controls in subsequent numerical modelling studies;
• to assess the potential for additional landslides within the region based on the physical conditions established at the existing slide site (e.g. geology, topography, structure, etc.).

In this respect, the project will involve several components of mapping and slope stability analysis including: detailed mapping of tensile, compressional and transverse shear features within the slide mass and near it's toe (approximately 1:100 scale); detailed mapping of the slide geometry, geology and geomorphology (approximately 1:500 scale); mapping of regional geology (1:10,000 scale) in a 2-4 km² area surrounding the slide; analysis of pre-slide conditions and stability assessment of similar slopes within the mapped region.

Additional tools such as GPS, aerial photographs and satellite imagery will also be used to aid in and supplement mapping. Collected data will be managed using either GIS or 3D geological modelling tools (e.g. GOCAD), and back analysis of the sliding conditions will be performed using analytical models based on limit equilibrium techniques.