The Functional Schematisation of the City as a Model for Anticipating Post-event Scenarios for Volcanic Hazards

Risk analysis requires the accurate characterisation of the hazardous events and their possible effects on the exposed elements. As demonstrated in recent events, volcanic activity may inflict several perturbations in urban functions, even compromising emergency-response actions. Thus, it is of the utmost interest to have holistic approaches that consider the city through its components for assembling feasible scenarios and performing mitigation strategies based on the system’s critical vulnerabilities. Failure Tree, Event Tree and Failure Mode and Event analysis are presented in this article as suitable approaches for conducting vulnerability-oriented research by using the village of San Pedro Tlalmimilulpan (México), in the context of the Popocatepetl volcano, as a case study. As demonstrated herein, these approaches facilitate the schematisation of the city based on the functions and infrastructures that, for a specific event scenario, are identified as critical for supporting sheltering and evacuation activities using such a traffic-light alert system. These analyses, supported by the existence of Risk Maps, reveal a series of proactive actions that would mitigate the adverse consequences of volcanic events. Furthermore, it is possible to find some highlights for designing a more efficient evacuation plan based on the most likely failures when analysing the singularities and location of a determinate village. The schematisation of urban functions in failure and event-based trees permitted identifying critical components of Tlalmimilulpan towards volcanic hazards, which may support the production of straightforward policies for risk mitigation and management in similar urban areas.