Principles of multi risk assessment

Several risks impend on the environment, on public and private properties, on strategic and priceless infrastructures in any inhabited area of our planet. They are generated by different sources, both natural and anthropogenic, and have different relevance depending on the synergy between the generated events and on the peculiar interaction with the region where they break out. The evaluation of risks related to different sources is generally done through independent analyses, adopting disparate procedures and time-space resolutions. In most of cases, only qualitative estimates of the risk level are available. In practice, this means that a potential ‘multi-risk’ index could be higher than the simple aggregation of single risk indexes calculated considering each source as independent from the others. A joint analysis and quantification of all the anthropogenic and natural risks which can affect a territory (multi-risk approach) is a basic factor for the development of a sustainable environment and land use planning as well as for a competent emergency management before and during catastrophic events. In this article, is proposed a new quantitative procedure for multi-risk assessment that makes easier the comparison among different threats and accounts for possible triggering effects