G. Vessia

Catalogue of Rainfall Events with Shallow Landslides and New Rainfall Thresholds in Italy

In Italy, rainfall-induced shallow landslides are frequent and harmful phenomena. The prediction of their occurrence is of social significance for civil protection purposes. For the operational prediction of rainfall-induced shallow landslides empirical rainfall thresholds based on the statistical analysis of past rainfall conditions that triggered slope failures are commonly used. The paper describes a catalogue of 1981 rainfall events, which caused 2408 shallow landslides in Italy in the period 1996–2012. Information on rainfall-induced landslides was collected searching chiefly online newspaper archives, blogs, and fire brigade reports. For each documented failure, we reconstructed the triggering rainfall conditions (rainfall duration D and cumulated rainfall E) using national and regional rain gauge networks. We analysed the rainfall conditions to determine new ED rainfall thresholds for Italy. The calculated thresholds can be implemented in a landslide forecasting system to mitigate landslide hazard and risk.

Methods and models for dealing with spatial variability in soil and rock characterisation: design, management and related hazards

Variability in time and space is a constant character of natural phenomena and geomaterials. When human activities within urbanised areas are concerned (such as construction of structures and infrastructures, civil protection actions against hazards and mining exploitation) a good strategy for soil management must take into account the inherent variable character of subsoil physical, chemical, minerological and mechanical properties. This special issue collects five different contributions from different research fields and professional experiences in terms of methods and models used to manage soil variability and related hazards. Parise proposes a procedure to estimate the susceptibility to natural and anthropogenic sinkholes in urban centres. The procedure recommends the need for accurate speleological, geological and geotechnical surveys (relieves) of the underground rock conditions before drawing zonation maps where the portion of territory prone to sinkhole development are contoured. Dematteis and Soldo introduce the R-index empirical method to estimate the reliability of the geological and geotechnical models used to design tunnels. It is needed especially to manage on going modifications to tunnel design due to unexpected spatial variations of rock conditions and properties. Two contributions are devoted to mining activities: Bauer et al. focus on the reliability of partial extraction of shaft support for pillar protection in copper mines; Namysłowska-Wilczyńska applies geostatistical tools to interpret the spatial variability of copper deposits in the mining areas. Finally, Marchesini et al. propose a method to manage the uncertainties in the definition of the bedding attitude for the production of morpho-structural domain maps through GIS instruments and their relationships with mapped landslide abundance. Through the different methods illustrated in this themed issue some strategies are shown to effectively model the variability of soil and rock behaviours in the subsurface. These are a compulsory step towards the design of efficient countermeasures to risks caused by natural and human induced hazards.

Reconnaissance of geotechnical aspects of the 2016 Central Italy earthquakes

Between August and November 2016, three major earthquake events occurred in Central Italy. The first event, with M6.1, took place on 24 August 2016, the second (M5.9) on 26 October, and the third (M6.5) on 30 October 2016. Each event was followed by numerous aftershocks. The 24 August event caused massive damages especially to the villages of Arquata del Tronto, Accumoli, Amatrice, and Pescara del Tronto. In total, there were 299 fatalities, generally from collapses of unreinforced masonry dwellings. The October events caused significant new damage in the villages of Visso, Ussita, and Norcia, although not producing fatalities, since the area had largely been evacuated. The Italy–US Geotechnical Extreme Events Reconnaissance team investigated earthquake effects on slopes, villages, and major infrastructures. The approach adopted to carry out post-earthquake reconnaissance surveys was to combine traditional reconnaissance activities of on-ground evidences and mapping of field conditions with advanced imaging and damage detection routines enabled by state-of-the-art geomatics technology. Presented herein are the outcomes of the post-event reconnaissance surveys conducted after both the August main shock and the October events, focusing on geotechnical aspects, such as earthquake-triggered slope failures, mud volcanoes, performance of different geotechnical structures (i.e., dams, retaining walls, rockfall barriers, road embankments) and building damage patterns related to site amplification.

Correction to: Reconnaissance of geotechnical aspects of the 2016 Central Italy earthquakes

Because of an error during the editorial process the first name initial of author Ernesto Ausilio was incorrectly given as A. (A. Ausilio) in the initial online publication. It should obviously be E. Ausilio. The original article has been corrected.

Introduction to a thematic set of papers on methods to assess the reliability of landslide hazard mapping

Landslide phenomena are widespread and cause extensive damage to the environment and to society every year (Cardinali et al. 2002; Carrara et al. 2003). Consequently, it is important to formulate appropriate strategies to mitigate and plan for landslides. The development of such a strategy relies on data provided by landslide hazard assessment and mapping—the number, locations, and magnitudes of mass movements during a reference time period. Different models, scales, and approaches for assessing landslide hazards have been proposed in the literature over the last 40 years (Corominas and Moya 2008; Fell et al. 2008 and references therein) due to the heterogeneity of landslide processes, the range of potential triggering factors (meteorological, seismic, anthropogenic), and the high variability observed in intrinsic features of landslides (e.g., size, velocity, lifetime, etc.). For this reason, the Joint Technical Committee on Landslides and Engineered Slopes (JTC-1; Fell et al. 2008) issued the Guidelines for Landslide Susceptibility and Hazard and Risk Zoning for Land Use, which summarizes the huge amount of previous experience gained in landslide mapping and related hazard calculations. Heuristic, physically-based, conceptual, and statistical models have been used to predict the spatial and temporal occurrence of landslides. Such models use a wide variety of information derived from field investigations, laboratory tests, proximal or remote sensing (e.g., data from drones and satellites, aerial data, etc.), and archive searches and analysis. The basic issue when assessing the occurrence of landslides is the accuracy and the reliability of the input data (Aleotti and Chowdhury 1999; van Westen et al. 2006; Fell et al. 2008) available for the study area. Moreover, as outlined by Aleotti and Chowdhury (1999), the input data for landslide hazard assessment should be updated over time with new information that continuously improves the reliability and the accuracy of the hazard models generated. Nonetheless, a degree of uncertainty is unavoidably associated with each landslide prediction due to the simplifications made during model development and the intrinsic variability of natural phenomena (Ardizzone et al. 2002; Guzzetti et al. 2006). Thus, the accuracy of hazard zoning strongly depends on the mapping scale used, which in turn depends on the zoning details. Three zoning levels can be distinguished according to Fell et al. (2008): regional, urban, and slopespecific. Studies performed at different scales require different methodologies associated with three different zoning levels—preliminary, intermediate, and advanced—according to Cascini (2008). A small-scale study can use only basic methods based on geological/geomorphological data and heuristic procedures, producing a preliminary zonation. A medium-scale study can employ intermediate methods such as statistical analyses and include more detailed information on soil and triggering factors, producing intermediate levels of zonation. Large and detailedscale studies can also utilize very detailed hydrogeological & G. Vessia g.vessia@unich.it