Soil characterization for landslide forecasting models: a case study in the Northern Apennines (Central Italy)

In this work we perform an assessment of the geotechnical and hydrological parameters affecting the occurrence of landslides. The aim of this study is to improve the reliability of the physically-based model HIRESSS (HIgh REsolution Slope Stability Simulator), for the forecasting of shallow landslides. The model and the soil characterization has been tested in northern Tuscany, in Italy, along the Apennine chain, an area that is historically affected by shallow landslides. In the area selected, the main geotechnical and hydrological parameters controlling the shear strength and permeability of soils have been determined by in situ measurements integrated by laboratory analyses. Around 60 survey points have been analyzed. The data obtained have been studied in order to assess the relationships existing among the different parameters and the bedrock lithology. Soil properties have been then statistically characterized and used to define the input parameters in the physical model, with the final aim of testing the ability of the model to predict shallow landslide occurrence in response of an intense meteoric precipitation. The rainfall event selected dates back to October 2010 when an intense precipitation affected the area, triggering around 50 reported shallow landslides. The geotechnical and hydrological data collected allowed to generate input map of parameters for the HIRESSS and the simulations showed substantial improvements in the results compared to the use of literature parameters.