Multi-hazard exposure characterization of urban settlements: a clustering proposal using open source data

A comprehensive understanding of essential characteristics of urban settlements, including typo-morphological, demographic, social, economic and institutional features is essential for developing effective strategies to enhance the resilience of urban settlements to natural hazards. The complexity and concentrated infrastructure in urban settlements can exacerbate the vulnerability to natural hazards . The high population density in cities increases the potential for casualties and impacts during events like earthquakes, floods, and hurricanes. Indeed, rapid urbanization often occurs without adequate consideration of natural hazard risks, leading to poorly planned structures and insufficient resilience measures. The interconnectedness of urban systems, including transportation, utilities, and communication, heightens the susceptibility of cities to systemic failures during disasters. Informal settlements and marginalized communities within urban areas are often disproportionately affected, lacking the resources and infrastructure to withstand natural hazards. The reliance on centralized resources and critical facilities can exacerbate vulnerabilities, as disruptions to these systems have cascading effects on the entire urban population.

In this study, a national-scale characterization of urban settlements in Italy is proposed using only open-source data. Urban settlements range from small towns and cities to large metropolis, with local government or administrative boundaries often defining their limits. Publicly available data on the built environment and population in urban areas is typically provided with reference to the administrative level. Information on the degree of urbanization, urban centeredness, residential population, and altimetric zone are used for a preliminary classification of Italian municipalities. Using such information, clustering of the municipalities is also carried out. Clustering urban settlements may help understand the most common types and features of urban settlements in a country.

For a proper characterization of an urban context, the impending hazard should also be identified. Due to the variability of geomorphological, climatic, and hydrological features, the incidence of different hazards throughout the Italian territory varies, as does their potential to generate significant impacts. A score-based procedure is proposed to allow the ranking of different hazards and to infer which hazards could be more relevant in a given urban context. For each relevant peril, the value of the corresponding intensity measure on the hazard map at a given return period is used to define a normalized score. Through scoring, a ranking of all Italian municipalities with respect to a given hazardous event is carried out.

This study was carried out within the RETURN Extended Partnership and received funding from the European Union Next-GenerationEU (National Recovery and Resilience Plan – NRRP, Mission 4, Component 2, Investment 1.3 – D.D. 1243 2/8/2022, PE0000005