UNDERSTANDING GEOENVIRONMENTAL DYNAMICS AND RISKS: THE CASSAS LANDSLIDE AND THE LARGE SLOPE INSTABILITIES OF THE MIDDLE SUSA VALLEY

Mountain regions have geological and geomorphological features that make them attractive for leisure and tourism activities; land occupation and seasonal population in many mountain areas are consequently increasing, together with impacts on the natural environment and geomorphological risks for human activities and infrastructures. This happens also because of enhanced environmental dynamics of mountain areas, due both to climate change, seismotectonics activity and lithostructural conditions. Sociological surveys have shown that "perceived risk", not "real risk", influences people's behavior towards natural hazards. Proper communication of hazard and risks studies can play an important role in raising awareness of tourists and residents in mountain areas of elevated risk and high geotouristic attraction. Based of this, we aim to: 1) contribute to the awareness-raising communication strategy of the RiskNat project (Interreg Alcotra 2007-2013, Action A.4.3) by synthesizing geoscience knowledge on slope instabilities of the Middle Susa Valley and information on models/prevention measures/warning systems of the Cassas landslide; and 2) achieve a new conceptual and operational discipline in the management of the geological heritage of the Middle Susa valley, by means of the development of techniques for recognizing and managing its rich geodiversity (ProGeoPiemonte Project, submitted to the "Progetti d'Ateneo" selection, operated by Università degli Studi di Torino and Compagnia di San Paolo Bank Foundation). By analyzing natural risk components in the Middle Susa valley, we outlined an approach to slope instabilities including: (a) natural hazards identification; (b) estimation of risk and vulnerability, and (c) evaluation of social consequences. (a) A review of geoscience literature on geodiversity, climate and landscape evolutionary stages and natural hazards of the area delineated the local and regional components of environmental dynamics. Significant landforms, agents, processes and factors have been described and mapped for reconstructing the evolutionary stages of the mountain environment. The long-term geomorphological changes have been represented through virtual landscapes of the Pleistocene glacial phases, from LGM to cataglacial stages. Relationships between deglaciation and deep-seated gravitational deformation at the Susa-Chisone divide have been explored also by analysis of lichen colonization on rock surfaces. (b) By integration of multispectral satellite images and multitemporal aerial photographs, static and dynamic conditions to Cassas landslide risk and related territorial vulnerability have been outlined. (c) Since vulnerability is a function of population, settlement and infrastructures, images of historical events of instability and documentation of related local damages have been collected. Panoramic view-points have been selected for a didactic trail to show the risk that people face in various circumstances and to present mitigation strategies. As a result of the systematic review of geoscience and natural hazards information, the Middle Susa valley became one of the 9 strategic geothematic areas have been selected by the ProGEO-Piemonte project to represent the geodiversity of our region, each characterized by high potential for enhancement of public understanding of science, and recreation activities supported by local communities. The visual representations and digital evolutionary models prepared for the RiskNat didactic trail and laboratory will contribute to the popularization of geological history, climate and environmental changes, natural hazards and related risk management practices in the Susa valley. A better recognition of the economic value of geodiversity and a stronger perception of natural risks will reduce local vulnerability to disasters and will support the territorial integrated quality management systems, suitable for tourism and sustainable development.