Geomorphology and stability analysis of the Charonnier landslide using remote sensing and in situ observations

Abstract

A combination of methods was applied in this research in order to investigate the geomorphology and stability of the Charonnier landslide occurred in early January 1994 after a prolonged wet period. This landslide is located in the mountainous environment of French Alps, an area vulnerable to mass movements. 29 collected samples and 6 saturated conductivity tests indicated that permeability and pore space decrease with depth suggesting the existence of macro-pores in the upper layers of soil.

Remote sensing techniques offer a variety of possibilities for studying mass movements on mountainous areas. Therefore, topography reconstruction of high resolution through photogrammetry methods used in this study for the detection and identification of surface objects. Moreover, mapping and monitoring of landslides was facilitated by the accurate and detailed photogrammetry products. A conventional UAV platform with a digital compact camera provided images for the construction of an elevation model. The derived products were of high spatial accuracy. Based on field observations and digital products of photogrammetry, conventional and modern techniques of mapping were performed and created a geomorphological map of large scale. The final map consists of five digital layers with respect to the assessment of landslide stability based on topographical, hydrological and morphological characteristics. The field survey and the evaluation of the geomorphological map denoted that there are signs of slow superficial movement not caused under the influence of stresses. They are probably caused by erosion processes (e.g. gully erosion on black marls) and thus, they cannot be attributed to landslide activity.

The strength parameters of effective cohesion (4 kPa) and internal friction angle (33.2o) were determined by shear tests on collected samples and were applied in the slope stability analysis. An analytical model was used to assess the stability conditions of the slope, by implementing the shear strength parameters and estimations about the rupture surface position revealing that the Charonnier landslide is currently considered stable. However, this can change in the future as erosion processes such as creep movements, influence the stability of the landslide.