Bianca Federici

From rainfall to slope instability: an automatic GIS procedure for susceptibility analyses over wide areas

The paper proposes an automatic procedure in geographic information system (GIS) for the analysis and prediction of landslides due to rainfall events over wide areas. It runs, for each unit cell, a hydrological balance based on the Curve Number method (USDA-SCS 1985–1986), computing the evolution of groundwater as a result of precipitation and then checks the overcoming, or not, of limit equilibrium conditions of the land in the domain of interest. The mathematical model was implemented in the free and open source GIS GRASS. For any sequence of consecutive days of rain, according to the conditions of soil moisture prior to the time history under study, the hydro-geotechnical model allows (1) the determination of the oscillations of the phreatic table, (2) the part of saturated soil and (3) the slope stability analysis, by taking into proper account the pore pressures buildup. The results of this procedure are returned in raster format, allowing an easy and intuitive interpretation of the land mass sensitivity to meteoric actions. The suggested procedure was applied on an extensive kinematic phenomenon surrounding the city of Santo Stefano d’Aveto (Liguria, Italy). The realized maps of landslide susceptibility are in excellent agreement with what is evident on site.

An Integrated Hydrological-Geotechnical Model in GIS for the Analysis and Prediction of Large-Scale Landslides Triggered by Rainfall Events

The proposed fully automatic procedure in a free and open source GIS, called GRASS, allows the evaluation of the propensity of a certain portion of land to slide due to rainfall events. Great attention has been devoted to define a proper infiltration model. Widespread slope stability analyses by a Global Limit Equilibrium method have been performed cell by cell. It is possible to take into account parameters that vary in vertical and horizontal directions. Moreover, the histories of rain (if necessary also of snowmelt) and the antecedent soil moisture condition are taken into account. There are no limits on the duration of the rain histories that can be considered. The computational effort is low even where large areas are divided into small pixels. The proposed procedure can be applied to any slipping site. In the present research an extensive kinematic phenomenon surrounding the city of Santo Stefano d’Aveto (Italy) was examined.

Evaluation of the Laser Response of Leica Nova MultiStation MS60 for 3D Modelling and Structural Monitoring

The use of Terrestrial Laser Scanner (TLS) is quite common for architectural surveys, however it requires to arrange special targets on the scanned object and to acquire several overlapping scans, which have to be aligned and edited externally. Recently, Leica released on the market a new kind of instrument, known as MultiStation (MS). It includes both the main characteristics of a TLS and of a Total Station (TS), meaning that no targets are required for the scan alignment, since the whole survey can be directly georeferenced. In this paper, some analyses about the use of this instrument for 3D modelling applications are discussed. First of all, the laser signal response is evaluated considering different materials, acquired using several combinations of distances and incidence angles. Then, the survey of the Casalbagliano Castle is presented and analyzed. All the performed tests show the great potentiality of the MS, allowing to reach accuracies of the order of few millimeters.

Oscillation of water table due to rainfall: an experience of modeling in GIS

A physically-based Integrated Hydrological-Geotechnical model (IHG) able to assess the rainfallinduced landslide susceptibility was developed, refined and applied in GIS environment along the past years (Passalacqua, 2002; Federici et al., 2014; Bovolenta et al., 2016), showing its reliability. It is a useful instrument to landslide susceptibility evaluations and land-use planning over wide areas. The present paper focuses on the modeling of water table oscillation due to rainfall, comparing different hydrological models.