Rockfall Hazard and Risk zonation at the Regional Scale

Rockfalls involve  volumes moving by free falling, bouncing, rolling, and sliding ( Cruden and Varnes, 1996 ). They are extremely frequent and have a long runout. In general, freeze and thaw cycles, rainfall and seismic shaking are among the most frequently recognized triggering, but also root growth or leverage in high winds, or progressive weathering of rock masses can cause detachments. Rockfalls are extremely important in alpine area and in Lombardy in particular. Since 1990s, a progressive increase in the number of rockfalls ( < 100.000m3) has been recorded at mid to high elevations in direct relation with rainfall and mean annual temperature. Future climate scenarios ( CH2011, 2011 ) include: rapid snowmelt periods, anticipated rainfall at the end of winter ( between +3.6% and +10.4% ), rainfall decrease in summer ( between -4% and -20.4% ) and increase in maximum temperatures. All these factors are and will be relevant at triggering rockfalls in different environments, endangering structures, infrastructures and lifelines, and most of the touristic resorts and structures at mid and higher elevations. It is expected that these changes will increase the frequency of events and that larger meteo-climatic changes will be related with the size of the rockfalls. Rockfall risk is managed in Regione Lombardia through land planning, protection countermeasures, and civil protection actions. Protection from rockfalls requires the characterization of rockfall hazard for different scenarios, spatial distribution, frequency and intensity of impacts, vulnerability of exposed elements, expected costs, and a cost-efficiency analysis of mitigation options. In real practice, rockfall problem is mainly managed through susceptibility-hazard assessments ( Crosta and Agliardi, 2003; Jaboyedoff et al., 2005 ) or engineered countermeasures ( Ritchie, 1963; Nichol and Watters, 1983; Calvetti and Di Prisco, 2009; Volkwein et al., 2009 ). Rockfall hazard is the probability that a specific location will be reached by rock fragments with a particular intensity ( Crosta and Agliardi, 2003; Jaboyedoff et al., 2005 ). Therefore, this probability is a combination of onset probability ( i.e. the probability of rockfall occurrence ) and runout probability ( i.e. the probability that falling blocks will reach specific locations ).





The main concept of the project is to develop the highest scientific knowledge for rockfall, to prepare valuable products by using all available official datasets in GIS format ( INSPIRE standards ) and to provide this knowledge to regional and municipal authorities, infrastructure operators, professional, and the civil society in general for strengthening risk management strategies and social resilience.

The scientific aims of the project are:

  • to explore the relationship between triggering events and rockfall onset, especially in environments characterized by different interacting factors
  • to study the effects of climate change on rockfall activity in prealpine and alpine areas as a consequence of temperature rise, rainfall pattern changes and permafrost degradation;
  • to implement a reliable and scientifically sound tool for 3D rock fall modelling at a local and regional scale to be readily used by regional agencies;
  • to study the role of rockfall for debris production within stream network, possibly leading to a drastic increase in debris flow hazard during intense rainfall events.





The implementation of the project will be done by the two partners in strict collaboration by using the facilities available at UNIMIB and POLIMI. The project is structured on 6 actions ( WP, work-packages ) modulated according to the following phases:

  • WP1: creation of a geodatabase of triggering events and rockfall events in Lombardy and conterminous areas
  • WP2: study of the relationship among triggering events and meteoclimatic conditions and the onset of rockfalls
  • WP3: implementation of the Hy-STONE code with new impact laws and to develop a dedicated modelling tool for regional authorities
  • WP4: assessment rockfall hazard and risk for the entire Regione Lombardia
  • WP5: development of future scenario of rockfall hazard and risk
  • WP6: dissemination of the methodology and results of the project to stakeholders, policy-makers, technicians, professionals, civil society.