Classification of Risks for Landslides in Slopes and Hillsides of Volcanic Nature in Macaronesia and Their Application to the Canary Islands

Abstract

Due to their genesis, volcanic rocks present some singularities that make their geotechnical characteristics significantly different from other more common types of massifs, such as sedimentary and metamorphic rocks. The formation mechanisms of volcanic rocks are varied, rapid, and, in general, of high energy. These processes give this type of rock a geotechnical behaviour and geomechanical properties that are totally different from those of other nonvolcanic materials, derived from their high heterogeneity and anisotropy. There are voids and cavities due to the alternation of strata of different competences and resistances, or susceptibility to erosion, and discontinuities and joints of very different genesis (of thermal origin, by mechanical forces, by erosive processes or by shrinkage—recrystallization). The phenomenology of the instability of blocks and stones is variable, which makes it very difficult to establish simple and concrete methodologies or procedures to study and analyse this problem. To date, the estimation of the risk of this type of phenomenon has been quantified using empirical methodologies; this approach is considered to be the most operative in responding to such a complex phenomenology in which a multitude of factors intervene. In the field of roads, the most widely used methods are RHRS and RHRON. Therefore, a new rockfall risk classification based on the RHRS (Rockfall Hazard Rating System) methodology is proposed in this article and specifically applied to the Canary Islands region.