New Developments in Rock Fall Hazard Assessment and Zoning: An Application of the Cadanav Methodology

Abstract

Rock fall hazard assessment and zoning are very important for an appropriate land use planning in mountainous areas. However, they are complex topics, and current methodologies adopted for producing zoning maps do not provide satisfactory results, due to assumptions and uncertainties involved in hazard assessment. This paper presents an application of the Cadanav methodology, which attempts at reducing hypotheses and related uncertainties particularly affecting the use of rock fall modelling results and the techniques for combining energy and frequency. This procedure allows for a quantitative evaluation of rock fall hazards based on the combination of relevant parameters also determined in quantitative terms. The hazard is obtained at any point of the slope by means of a new tool defined as “hazard curve”. Aimed to hazard degree assessment and zoning at the local scale, the Cadanav methodology is presented with reference to a case study set in the Canton of Valais (Switzerland). Different scenarios in terms of rock fall frequency are considered, to illustrate how this procedure can also describe the way hazard evolves along the slope, if a change in the probability of failure occurs.