Integrated Approaches to Assessing the Impacts of Multirisk events initiated by Natural Hazards

The occurrence of disasters related to natural hazards has increased in recent decades due to the growing exposure of urban population and effects of climate change. This context can increase highly complex risks and create multidimensional vulnerabilities. Technological risks further aggravate these considerations, especially as the distance between inhabited and industrial areas has been decreasing over time and as the number of infrastructures and their interrelationships has been increasing. All those complex systems, which could act in combination - with or without coincidence in time, could impact potentially dependent elements at risk. Indeed, under certain conditions, different combinations of natural and technological hazards are likely to occur, e.g., an earthquake followed by a tsunami, floods impacting facilities, domino effect between industries, cascade effect between infrastructures. When these complexities are not properly accounted for by decision-makers, it can lead to ineffective or even misguided risk management strategies. This situation is visible in South of France (SF), a region prone to natural hazards such as forest fires, torrential floods, marine submersion, etc. Moreover, the analysis of 31 semi-structured interviews with local, departmental, and regional actors involved in risk management across three SF territories has shown that the current risk management approach facilitates an effective transition to a multi-risk strategy. However, the existing tools are insufficient and require improvements to ensure effective multi-risk management. This study seeks, by integrating different approaches (dependability analysis, multi-hazard modeling, geographical representations), to assess the potential consequences of the multi-risk events in and local scale considering the Influence of territorial specificities and stakeholder areas of intervention. We analyze the complex cause-and-effect interrelationships of the critical infrastructures (e.g. transportation networks, energy systems, water supply, and emergency services) exposed to hazardous events and estimate the resulting disruptions to basic services for the population. We use an example of a virtual coastal city typical of the South of France, exposed to phenomena like flood, submersion and technological risk to simulate various scenarios of multi hazards in order to integrate, describe and quantify their cascading impacts