Constitution of a multicentennial multirisk database in a mountainous environment from composite sources: the example of the Vallouise-Pelvoux municipality (Ecrins, France)

Abstract

To develop efficient mountain risk management strategies, an obvious, yet tremendously difficult prerequisite is the constitution of comprehensive databases of past events and their impacts over long-time frames. However, existing records are often too short and siloed between different data providers and/or as function of hazards. To fill this gap, a methodology based on the combination of scattered pre-existing records with further archival research is proposed and used to populate a well-structured multirisk database covering the period 1600–2020 AD in a municipality of the French Alps – Vallouise-Pelvoux. Results include 2131 events related to rockfall, landslides, snow avalanches, floods (including debris flows) and glacial hazards, with documentation of possible interactions between hazards, their characteristics and detailed impacts. The combined use of different sources – and in particular archival searches – and their cross-referencing therefore provides a detailed record of past events that goes far beyond any inventory existing at the local scale. The analysis suggests that the distribution of events results from the combined effect of hazards, sources and human activities putting assets at risk, with a primary effect of sources. The methodology opens perspective for multirisk assessment in mountain territories and can be usefully transferred to other case studies.