Spatial patterns of landslide dimension: A tool for magnitude mapping

AbstractThe magnitude of mass movements, which may be expressed by their dimension in terms of area or volume, is an important component of intensity together with velocity. In the case of slow-moving deep-seated landslides, the expected magnitude is the prevalent parameter for defining intensity when assessed as a spatially distributed variable in a given area. In particular, the frequency–volume statistics of past landslides may be used to understand and predict the magnitude of new landslides and reactivations. In this paper we study the spatial properties of volume frequency distributions in the Arno river basin (Central Italy, about 9100km2). The overall landslide inventory taken into account (around 27,500 events) shows a power-law scaling of volumes for values greater than a cutoff value of about 2×104m3. We explore the variability of the power-law exponent in the geographic space by setting up local subsets of the inventory based on neighbourhoods with radii between 5 and 50km. We found that the power-law exponent α varies according to geographic position and that the exponent itself can be treated as a random space variable with autocorrelation properties both at local and regional scale. We use this finding to devise a simple method to map the magnitude frequency distribution in space and to create maps of exceeding probability of landslide volume for risk analysis. We also study the causes of spatial variation of α by analysing the dependence of power-law properties on geological and geomorphological factors, and we find that structural settings and valley density exert a strong influence on mass movement dimensions

Geomorphological investigations on landslide dams

Background: The study of past landslide dams and their consequences has gained a considerable significance for forecasting induced hydraulic risk on people and property. Landslide dams are rather frequent in Italy, where a broad climatic, geological and morphological variability characterize different part of the peninsula, and have already been studied in literature, focusing different geographical regions with different levels of detail. In order to develop specific tools to assess the landslide dam formation and stability, the first step is to realize a large data archive including a big number of data, collected with a consistent methodology to standardize the quality. Description: For this reason, this paper reports the results of an extensive bibliographic work and geomorphologic investigation on landslide dams that lead to the development of the wider systematic inventory in Italy. Through the revision and the update of scientific works and historical reports, three hundreds of landslide dams from the Alps to the Southern Apennine and Sicily were identified. During investigations and through cartographic and aerial photos interpretation, several geomorphic parameters of the landslide, the dam body, the valley and the lake, if any, have been determined, or estimated using historical and bibliographical documents analysis. Conclusions: The collected data were resumed in a database, formed by 57 information fields easy to collect and measure to privilege intuitive usability and future implementation. In order to describe the characteristics of landslide dams in Italy some specific analysis on the different types of landslide movements and their volume, the dam longevity, the main triggers and their geographical distribution were carried out

Risk analysis for the Ancona landslide—II: estimation of risk to buildings

This paper illustrates the quantitative estimation of specific risk (i.e., the product of hazard and vulnerability) for 39 buildings located upon the Ancona landslide based on the characterization of landslide kinematics presented in a companion paper. Hazard is quantified based on intensity, intended as the damaging potential of the kinetic and/or geometric attributes of the landslide, and is expressed in terms of expected exceedance of preset cumulative displacement thresholds for a set of five reference time intervals, ranging from 1 to 100 years. The estimation of hazard relies sequentially on (1) Monte Carlo simulation of displacement series, with sampling distributions of average yearly displacement defined on the basis of the statistical processing of inclinometer and radar interferometer data; and (2) the subsequent spatialization of displacement using radial basis interpolation as described in the companion paper. The vulnerability of the set of buildings relies on a quantitative model in which vulnerability is a function of landslide intensity and the resilience of the buildings. Resilience is a function of a set of indicators including structural type, age, and foundation type and is temporally variable due to the progressive structural degradation. Hazard, vulnerability, and specific risk are estimated for the set of five aforementioned reference time intervals. The magnitude and temporal dependence of hazard, vulnerability, and specific risk are assessed critically