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Abstract Background Rockfalls pose a serious threat along the main road network, representing a major hazard in mountainous territory and causing damage and victims. Currently, susceptibility mapping represents a starting point to identify areas more susceptible to rockfall occurrence, a key approach in land use planning and risk management. Despite the extensive use of these maps by decision makers and administrators, the usability of such maps over time and their reliability represent a poorly discussed and examined feature. Methods Here, we proposed a-posteriori analysis of a three-year-old rockfall susceptibility map, generated along the main road network of the Aosta Valley, an alpine region of north-western Italy. To verify map consistency over time, we implemented a dual-analysis in GIS-environment and by text mining, to respectively analyse the geocoded data and textual information derivable from the regional landslide inventory. The first one allowed us to extract rockfall events occurred after the susceptibility map generation. By this way, we operated to spatially and temporally verify the map consistency. Jointly, the textual information reported in the Event Description Form, linked to each geocoded event, are being exploited. This allowed us to derive relevant information about occurred damage and their degree, presence of protective measures or secondary roads, i.e. involvement of, farm or forestry, road. Results The implemented approach allowed us to prove the quality of the previous map in terms of reliability, robustness and degree of fitting respect to the succession of rockfall occurrence over time. After only three years as many as 198 rockfall events have been occurred and collected since the map was generated. Particularly, 80% of rockfall fit with “high” and “very high” susceptibility classes, and pointed out large involvement of main roads in rockfall occurrence, representing the most affected target with damage to road pavement and vehicles, as well as a relevant involvement of existing rockfall barriers and of the dense network of forestry roads and footpaths that characterize this alpine region. Results The proposed approach representing a starting point in landslide susceptibility map verification and usability as valid instrument for a reliable land planning.

The presence of trees along the slope and block fragmentation at impact strongly affect rockfall dynamics and hazard as a consequence. However, these phenomena are rarely simulated explicitly in rockfall studies. We performed rockfall simulations by using the 3D rockfall simulator Hy-Stone, modeling both the presence of trees and fragmentation through specific algorithms implemented in the code. By comparing these simulations with a more classical approach that attempts to account implicitly for such phenomena in the model parameters and by using a new probabilistic rockfall hazard analysis (PRHA) method, we were able to quantify the impact of these phenomena on the design of countermeasures and on hazard. We demonstrated that hazard changes significantly when accounting explicitly for these phenomena and that a classical implicit approach usually overestimates both the hazard level and the 95th percentile of kinetic energy, leading to an oversizing of mitigation measures.

Rockfalls are a major hazard in mountain areas. They can endanger human settlements and infrastructures, and, every year, cause multiple damage and victims. An investigation of those areas more susceptible to rockfall represents a key approach to improve the analysis and management of rockfall impact and consequences. The proposed procedure involves the study of occurred rockfall databases and thematic maps to compute a susceptibility map, by the employment of Analytical Hierarchic Process. The computation is focused on the road network of Aosta Valley Region (northwestern Italy) and its proximity. The model results highlight the importance of morphometric factors on the investigated phenomena. The outcomes of the analysis were also validated by comparing rockfall databases with the receiver operating characteristic curve, in order to confirm their reliability. The results of the procedure are a starting point for a detailed planning action in order to manage the hazard related to these phenomena.

Straightforward communication of monitoring results is of major importance in emergency scenarios relevant to large slope instabilities. Here we describe the communication strategy developed for the Mont de La Saxe rockslide threatening La Palud and Entrèves hamlets in the Courmayeur municipality (Aosta Valley, Italy). Starting from the definition of actions and needs of the landslide management team, including scientists, technicians, civil protection operators, decision makers, and politicians, we show that sharing and disseminating ad hoc information simplifies the understanding of the landslide evolution, as well as the correct communication of the level of criticality.

Deep-seated Gravitational Slope Deformations (DsGSDs) are huge ground-deformation slow evolving phenomena, highly widespread in alpine territory. Their long-lasting evolution, with continuous deformation rate, may represents a natural hazard, able to endanger various anthropic structures and infrastructures. Until today, the development of technical and regulatory tools, aimed to effectively manage the interactions between DsGSDs and anthropic elements, has been generally lightly considered in risk management and land use planning. The definition of the type and severity of impacts on the anthropic elements, becomes increasingly important in terms of urban planning and risk management, and deserve an update in the current adopted procedures. Focusing on the Western Italian Alps, we implemented an interdisciplinary analysis, based on multi-source data, by means of geoinformatics, remote sensing and archive consultation approaches. Intersecting DsGSDs available information with the urbanized territory in a Geographic Information System environment, we obtained, despite the high data heterogeneity, an overall framework of the existing interactions. Specifically, we defined the interactions between these large phenomena and buildings, roads and rail networks, and linear infrastructures, as penstocks, waterworks or dams, also highlighing the state of activity of the inventoried phenomena. Moreover, we analysed the degree of the DsGSD impacts on the anthropic elements, detecting and classifying all the documented damages within the Italian Western Alps territory. The obtained results highlight the need for an innovative approach in DsGSDs risk assessment, both in terms of the definition of their behavior over time and of their impacts on the anthropic elements, for a more effective land use planning and a proper handling of these phenomena in the legislation framework., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)