Search

Rockfalls pose a significant threat to life and property, although significant advances in rockfall protection have been made in the past decade. Determining rockfall processes and related hazard, however, remains a difficult task, because of the complexity and intrinsic stochastic nature of the physics involved. Appropriate application of rockfall modelling tools requires a thorough understanding of their logic, assumptions, advantages, and limitations, as well as careful assessment of rockfall sources, block and slope characteristics, and model calibration data. This chapter provides a discussion of major issues in rockfall definition, characterisation, and modelling, with special emphasis on rockfall runout. Our discussion is supported by modelling examples carried out using the 3D simulator Hy-STONE. Different modelling approaches are critically evaluated, including the empirical shadow angle method, and 2D and 3D mathematical models. Application of the shadow angle concept requires the user to be aware of several issues related to definition of the shadow angle and the effects of morphological constraints. Most limitations of empirical approaches can be overcome with mathematical models that account for slope morphology and roughness, energy dissipation at impact or by rolling, and the effects of vegetation, block fragmentation, and block-structure interaction. We discuss different modelling approaches and calibration problems and the important dependency of model parameters and results on correct characterisation of topography.

Giant, deep-seated gravitational slope deformations (DSGSD) affecting entire high-relief valley walls are common in alpine areas, and influence the evolution of mountain landscapes and the related hazards. In the last few years, new characterisation approaches and emerging technology shed new light on the occurrence, distribution, activity, and mechanisms of these spectacular slope failures. This chapter is aimed at providing an overview of alpine DSGSD, as well as a discussion of outstanding issues and future research needs. We review the definition of DSGSD and its typical features, field evidence, settings, and mechanisms. We discuss the distribution and controls on DSGSD occurrence based on the analysis of the first-ever orogen-scale inventory of these phenomena, including over 900 individual phenomena in the European Alps. We demonstrate that DSGSDs are widespread in active orogenic settings and chiefly occur in formerly glaciated areas under significant structural controls, and show that alpine DSGSDs are often active phenomena with a engineering significance. We use the emblematic case study of the Cima di Mandriole sackung to illustrate the complex relations among rock structure, the morpho-climatic evolution of Alpine valleys, and man-made structures, and point out future research needs.