CERCA (Cascading Effects in Risk Consequences Assessment): an operational tool for geo-hydrological scenario risk assessment and cascading effects evaluation

Building multiple, complex risk scenarios is a priority for the improvement of the effectiveness of early warning systems and technical countermeasure designs to detect phenomena associated with severe weather events, such as floods and landslides. This study presents CERCA (Cascading Effects in Risk Consequences Assessment), a methodology for the characterisation of event scenarios that is consistent with the current Italian Civil Protection Guidelines on the national warning system for weather-related geo-hydrological and hydraulic risks. The aim is to propose a simple, effective, multi-scale operational tool that can be adapted to multiple purposes. CERCA is structured as a tool for a typical ‘scenario analysis’ in a multi-hazard context through the qualitative assessment of cascading effects and consequences for different categories of elements at risk, particularly in terms of human losses. The framework is assessed on a case study concerning a local event in Rossano (Calabria, Italy) and on a number of damaging events that occurred in Italy during the period 2004–2021. The proposed approach can be effective in processing post-disaster information, monitoring the real-time evolution of critical situations, creating priority lists for decision-making, and providing general dependency matrices to be used for ‘ex-ante’ definitions of scenarios.