The last two years have set a sad record in terms of the number and scale of natural disasters and have clearly demonstrated the high vulnerability of the global economy to their impact. Amongst the most serious consequences have been the so-called natural-technological or NaTech disasters that occur when natural hazards trigger accidents and disasters at technological and critical infrastructure facilities, such as nuclear power plants, chemical plants, oil refineries and pipelines. This also raises the issue of the increasing realisation that a “multi-type” framework is necessary if one is to more effectively assess the consequences of, and mitigate against, natural and anthropogenic disasters. Such a framework would need to consider the causal, spatial and temporal relationships that exist between different hazards and risks, leading to the situation where simply the sum of individual risks underestimates their true impact, as for example observed in the cases of the 2005 Katrina hurricane and the 2011 Tohoku earthquake.
The need for such a framework will only increase in the future, given how the number and size of urban centres is increasing throughout the world. The linkages between natural hazards at a regional scale and infrastructure risks at a local scale in urban areas can be therefore considered as crucial to assess possible scenarios in the future.
The main goals of this session are (1) to summarize case studies of relationships between natural hazards and technological disasters and to encourage a discussion about tools and methods to prevent or minimize their consequence, and (2) present the latest developments in the areas of multi-type hazard and risk assessment. The issues of particular concern are cascade effects, including the interactions between natural and NaTech events, uncertainty propagation and, temporal dependency, which would also require examining short-term sequences where hazards occur almost simultaneously or are triggered by one another, to longer-term scenarios that may cover several months or years.