Settimio Ferlisi

Recommendations for the quantitative analysis of landslide risk

This paper presents recommended methodologies for the quantitative analysis of landslide hazard, vulnerability and risk at different spatial scales (site-specific, local, regional and national), as well as for the verification and validation of the results. The methodologies described focus on the evaluation of the probabilities of occurrence of different landslide types with certain characteristics. Methods used to determine the spatial distribution of landslide intensity, the characterisation of the elements at risk, the assessment of the potential degree of damage and the quantification of the vulnerability of the elements at risk, and those used to perform the quantitative risk analysis are also described. The paper is intended for use by scientists and practising engineers, geologists and other landslide experts.

Seasonal effects of rainfall on the shallow pyroclastic deposits of the Campania region (southern Italy)

The shallow deposits of unsaturated pyroclastic soils covering the slopes in the Campania region (southern Italy) are systematically affected by various rainfall-induced slope instabilities. The type and triggering of these instabilities depend on several factors, among which in situ soil suction—as an initial condition—and rainfall—as a boundary condition—play a fundamental role. Based on the available database—which includes a comprehensive catalogue of historical data, in situ soil suction measurements and soil laboratory tests along with the results of geomechanical analyses—this paper discusses the relationships among in situ soil suction and rainfall conditions and induced slope instability types. The goal is to reach a better understanding of past events and gain further insight into the analysis and forecasting of future events. In particular, the paper outlines how the season strongly affects the spatial distribution and the type of slope instability likely to develop. For example, erosion phenomena essentially occur at the end of the dry season and originate hyperconcentrated flows while first-time shallow slides prevail in the rainy season and later propagate as debris flows or as debris avalanches.

Subsidence monitoring in Sarno urban area via multi‐temporal DInSAR technique

In this study Differential Interferometric Synthetic Aperture Radar (DInSAR) is used to investigate the effects of a subsidence phenomenon – related to groundwater withdrawal –on ancient low‐rise masonry buildings located in the urban area of Sarno, Italy. ERS‐1/2 SAR data from 1992 to 2002 were analysed and results were validated with geodetic data. The results encourage future developments for study and use of the multi‐temporal DInSAR technique in the mitigation of subsidence risk.

Individual and societal risk owing to landslides in the Campania region (southern Italy)

This paper deals with the estimation of both individual and societal risks owing to landslides in the Campania region (southern Italy) thanks to the availability of an extensive catalogue of historical incident data spanning from the 5th century up to now. Individual risk is estimated by computing the landslide mortality rate. Societal risk is measured by plotting the annual frequency F of events causing N or more fatalities against the number N of fatalities (i.e. an F–N curve). The results obtained show that in Campania both individual and societal risks owing to landslides are very high when compared to similar risks of the Italian territory. Moreover, the analysis of the incident data clearly highlights the most prone areas to catastrophic events, essentially related to the occurrence of flow-like fast-moving phenomena, where the societal risk is proved to be one of the highest in Europe.

Detection and monitoring of facilities exposed to subsidence phenomena via past and current generation SAR sensors

The identification of facilities in areas affected by subsidence phenomena represents a fundamental activity in processes dealing with land management. For this kind of phenomena, the analyses may be hampered by the lack of official subsidence zoning maps because of the wide extension of the affected areas. This is mainly due to the costs necessary for measurements and surveys to be carried out via conventional in?situ techniques which can turn out to be unaffordable for the authorities in charge of land management. In this regard, during the last decade the use of remote sensing data, such as medium resolution synthetic aperture radar (SAR) images processed via differential interferometry algorithms (DInSAR), has proven its benefits for the detection and monitoring of facilities (i.e., buildings and infrastructures) in subsiding areas. Currently, the improved resolution and coverage of the ultimate generation SAR sensors seem very promising for consequence analyses of facilities, although displacement time series are still limited for long-term studies. In this paper, analyses of DInSAR data acquired via both medium (ERS-ENVISAT) and high (COSMO-SkyMed) resolution sensors are carried out over a densely urbanized flat area in southern Italy so as to show how the appropriate use of DInSAR data at different scales can valuably help in the detection and monitoring of damageable facilities.

Expert engagement in participatory processes: translating stakeholder discourses into policy options

This paper demonstrates an innovative role for experts in supporting participatory policy processes with an application to landslide risk management in the Italian town of Nocera Inferiore. Experts co-produce risk mitigation options based on their specialized knowledge taking account of local knowledge and values by directly coupling stakeholder discourses with option design. Drawing on the theory of plural rationality and based on a literature review, interviews and a public questionnaire, stakeholder discourses are elicited on the landslide risk problem and its solution. Armed with the discourses and in close interaction with stakeholders, experts provide a range of technical mitigation options, each within a given budget constraint. These options are subsequently deliberated in the participatory process with the intent of reaching compromise recommendations for landslide risk mitigation. As we show in an accompanying paper, “Compromise not consensus. Designing a participatory process for landslide risk mitigation” (this issue), the provision of multiple co-produced policy options enhances stakeholder deliberation by respecting legitimate differences in values and worldviews.

Empirical fragility and vulnerability curves for buildings exposed to slow-moving landslides at medium and large scales

Slow-moving landslides yearly induce huge economic losses worldwide in terms of damage to facilities and interruption of human activities. Within the landslide risk management framework, the consequence analysis is a key step entailing procedures mainly based on identifying and quantifying the exposed elements, defining an intensity criterion and assessing the expected losses. This paper presents a two-scale (medium and large) procedure for vulnerability assessment of buildings located in areas affected by slow-moving landslides. Their intensity derives from Differential Interferometric Synthetic Aperture Radar (DInSAR) satellite data analysis, which in the last decade proved to be capable of providing cost-effective long-term displacement archives. The analyses carried out on two study areas of southern Italy (one per each of the addressed scales) lead to the generation, as an absolute novelty, of both empirical fragility and vulnerability curves for buildings in slow-moving landslide-affected areas. These curves, once further validated, can be valuably used as tools for consequence forecasting purposes and, more in general, for planning the most suitable slow-moving landslide risk mitigation strategies.

The Use of DInSAR Data for the Analysis of Building Damage Induced by Slow-Moving Landslides

The paper aims at checking the contribution that DInSAR data, processed via different algorithms, can provide to the analysis of damages recorded to buildings located in slow-moving landslide affected areas. For this purpose, an urban area in Calabria region, southern Italy, was selected due to the availability of both DInSAR data since 1992 and historic information concerning damage data recorded via municipal ordinances. The combination of DInSAR data and the results of supplementary damage surveys allowed the preliminary investigation of a cause (maximum velocity)—effect (damage) relationship which, once validated, can be valuably used for damage analysis and forecasting.

Quantitative risk analysis for hyperconcentrated flows in Nocera Inferiore (southern Italy)

This paper reports on a quantitative estimation of the risk to residents at the toe of Mount Albino, a carbonatic relief covered by shallow deposits of pyroclastic soils, which threatens the municipality of Nocera Inferiore (southern Italy). The quantitative risk analysis (QRA) focuses on one type of mass transport phenomena typical for the context at hand, namely the hyperconcentrated flows. The methodological approach includes three main steps: hazard analysis, consequence analysis and risk estimation. Based on historical incident data, the hazard analysis makes use of a high-resolution digital terrain model and advanced models that incorporate relevant geological and geotechnical input data collected via in situ investigations and laboratory tests. The consequence analysis takes into account information on the exposed persons (age, gender) and their vulnerability. The estimated risk to life is calculated at the individual level (risk to the average and most exposed person). The reported procedure is one of the first QRA’s applications to instabilities which potentially affect natural slopes in Italy, and it was successfully used as technical basis for a public participatory process in Nocera Inferiore, designed and developed to support decisions about risk mitigation measures.

Analysis of building vulnerability to slow-moving landslides via A-DInSAR and damage survey data

The paper presents a procedure for the analysis of building vulnerability to slow-moving landslides via A-DInSAR and damage survey data. For this purpose, a test site in Calabria region (southern Italy) affected by slow-moving landslides, which over the time caused severe damage to buildings, was selected. The availability of remote sensing data such as those derived from the processing of Synthetic Aperture Radar images via Advanced Differential Interferometry techniques (A-DInSAR) and information concerning damage severity suffered by the facilities, collected by in situ damage surveys, allowed investigating the cause (differential settlement)—effect (damage) relationship. Then, empirical fragility curves for both reinforced concrete and masonry buildings were generated. These latter, once further validated, can be valuably used for damage analysis and forecasting purposes and framed within procedures for risk analysis and management over urban landslide-affected areas.