Multi-hazard system of a high Alpine valley: construction of an event chronology from different sources

Mountain regions are subject to highly damaging hydrological and gravitational hazards. This exposure is due to their biophysical and societal characteristics. It is essential for a sustainable management of these risks to consider the natural risk as the result of complex interactions within the risk system, which is composed of a natural and a societal subsystem. In this way, it is possible to adopt a dynamic approach to the risk system by placing the phenomenon in an evolutionary context. We can therefore consider its trajectory according to the socio-environmental dynamics that influence it.

Studying these risk systems over the long term is necessary to understand their evolution and to anticipate future ones in order to guarantee the sustainability of mountain socio-ecosystems, and requires an interdisciplinary approach between geography and history.

The study of the trajectory of a multi-hazard system is being carried out in the Commune of Vallouise-Pelvoux, a high Alpine valley in the Écrins massif, France. This territory was chosen because it is subject to various risks that occur over a wide range of altitudes, its recent socio-economic development is mainly based on tourism, and it is marked by glacial recession, but also because we were aware of the availability of several sources allowing the production of event and multirisk chronologies.

The first stage of the research consisted in the production of a multi-hazard event chronology over 420 years (1600-2020). This database was built from various resources. On the one hand, from existing databases produced by public services and organizations such as the French Forest Office (ONF) specifically the mountain land restoration service (RTM) or the departmental councils. On the other hand, archival research was carried out in the municipal archives of Vallouise-Pelvoux and the departmental archives of the Hautes-Alpes.

After analysis of all available sources, the data collected was processed in various ways. Indeed, sources of different forms and origins requires standardization of the information to make it comparable and usable. The chronology was also subjected to a critical analysis : are the sources authentic? Reliable? What factors might influence them? 

Once this chronology of events in Vallouise-Pelvoux has been contextualized (changes in the natural and societal systems of the Commune), a first statistical analysis of the risks identified and the damage caused will be presented. In the future the data will be used to analyze the trajectory of the system.