Evaluating Rockfall Risk: Some Critical Aspects

Abstract

Rockfalls evolve rapidly and unpredictably in mountain environments and can cause considerable losses to human societies, structures, economical activities, and also natural and historical heritage. Rockfall risk analyses are complex and multi-scale processes involving several disciplines and techniques. This complexity is due to the main features of rockfall phenomena, which are extremely variable over space and time. Today, a considerable number of methods exists for protecting land, as well as assessing and managing the risk level. These methodologies are often very different from each other, depending on the data required, the purposes of the analysis, and the reference scale adopted, i.e., the analysis level of detail. Nevertheless, several questions still remain open with reference to each phase of the hazard and risk process. This paper is devoted to a general overview of existing risk estimation methodologies and a critical analysis of some open questions with the aim of highlighting possible further research topics. A typical risk assessment framework is exemplified by analyzing a real case study. Each step of the process is treated at both the detailed and the large scale in order to highlight the main characteristics of each level of detail.

Preliminary Modeling of Rockfall Runout: Definition of the Input Parameters for the QGIS Plugin QPROTO

“…The following three raster maps (v_min, v_mean and v_max) concern the minimum, mean and maximum velocity, respectively, evaluated in each cell by using Equation (1). Based on these last three rasters, the corresponding energy raster maps (e_min, e_mean and e_max) are obtained adopting Equation (2). Furthermore, the two time-independent hazard maps (w_en and w_tot_en) are provided by multiplying the detachment index DI and the kinetic energy in each cell of the runout area.…”

“…The assessment of susceptibility and hazard are the most challenging issues in the field of rockfall risk estimation [1]. In particular, the study of the hazard level requires three main steps [2]: (i) the spatial identification of the involved areas; (ii) the computation of the rockfall intensity (measurable via the estimation of the kinetic energy of the falling blocks); (iii) the definition of the temporal occurrence of the phenomenon.…”

“…These models are generally used on large scales (i.e., site-specific) and local scales, following the recommendations of Corominas et al (2014) [3] for detailed risk analyses or to design protection works. Even more simplified models are used on small scales for territorial planning and preliminary study purposes [2][3][4]. Necessarily, in these cases, the runout model should be both simple and reliable in order to overcome the limited availability of data and their epistemic uncertainties.…”

Fragmented Rockfall Volume Distribution from Photogrammetry-Based Structural Mapping and Discrete Fracture Networks

“…Quantifying rockfall hazard and risk, and the design of rockfall mitigation structures, require information about the falling block volumes (and mass), their fragmentation during motion, and 2 of 18 their frequencies [13,[20][21][22][23][24]. Information on rockfall volumes and fragmentation can be gathered from comprehensive records or estimated through surveying fallen blocks along known rockfall trajectories [6,11,13,16,20,23].…”

Rock Mass Characterization of Karstified Marbles and Evaluation of Rockfall Potential Based on Traditional and SfM-Based Methods; Case Study of Nestos, Greece

“…The methodology that is usually followed for the evaluation of rockfall potential within an area is discriminated in several stages, including a detailed engineering geology field survey and analysis of the data obtained during this survey, identification of the failure type mechanism, e.g., wedge, planar slide, toppling, and the assessment of the rockfall trajectory and the evaluation of critical parameters like the kinetic energy and the bounce height of the detached rock (e.g., [1]).…”