Geological Assessment and Physical Model of Complex Landslides: Integration of Different Techniques

Abstract

Complex landslides usually need to be investigated in depth in order to understand the geological setting that led to their formation and influenced their development. The knowledge of the landslide structure and history is the key point to understand potential future development and evolutions. Classical geological tools and campaigns can only give a partial insight and integration of different survey techniques arises as a crucial point to improve knowledge and overcome traditional techniques' shortcomings. Here, the Torrioni di Rialba (Italy) case study is presented. A vertical 135 m-high rock cliff in Abbadia Lariana, Northern Italy, is suspected to be potentially unstable, although no information about the geological setting is available. Although the landslide has not shown activity evidences in the last decade a possible collapse threatens a narrow corridor of extreme importance. The urge to better understand landslide causes led to start a broad campaign of surveys. Geological investigations were conducted along with geophysical surveys, namely seismic tomography and several electrical soundings, to give an insight in the inner slope structure and were calibrated drilling two boreholes on the slope. An accurate Lidar survey of the area as well as lake bathymetry near the landslide spot allowed for precise geometry assessment of the area to correctly locate information gathered. In this work the weak and strong points of each choice is debated in order to highlight uncertainty in the decisional process and to define good practice and caveats. The entire work, which took four years, due to economical and logistic limitations is critically reviewed and the better choices are underlined.