Multi-risk assessment in a historical city

Abstract

Natural hazards pose a significant threat to historical cities which have an authentic and universal value for mankind. This study aims at codifying a multi-risk workflow for seismic and flood hazards, for site-scale applications in historical cities, which provides the Average Annual Loss for buildings within a coherent multi-exposure and multi-vulnerability framework. The proposed methodology includes a multi-risk correlation and joint probability analysis to identify the role of urban development in re-shaping risk components in historical contexts. The workflow is unified by exposure modelling which adopts the same assumptions and parameters. Seismic vulnerability is modelled through an empirical approach by assigning to each building a vulnerability value depending on the European Macroseismic Scale (EMS-98) and modifiers available in literature. Flood vulnerability is modelled by means of stage-damage curves developed for the study area and validated against ex-post damage claims. The method is applied to the city centre of Florence (Italy) listed as UNESCO World Heritage site since 1982. Direct multi-hazard, multi-vulnerability losses are modelled for four probabilistic scenarios. A multi-risk of 3.15 M€/year is estimated for the current situation. In case of adoption of local mitigation measures like floodproofing of basements and installation of steel tie rods, multi-risk reduces to 1.55 M€/yr. The analysis of multi-risk correlation and joint probability distribution shows that the historical evolution of the city centre, from the roman castrum followed by rebuilding in the Middle Ages, the late XIX century and the post WWII, has significantly affected multi-risk in the area. Three identified portions of the study area with a different multi-risk spatial probability distribution highlight that the urban development of the historical city influenced the flood hazard and the seismic vulnerability. The presented multi-risk workflow could be applied to other historical cities and further extended to other natural hazards.

Multi-attribute-based procedure for seismic risk scenario in a historical area

“…The present research proposed a seismic risk assessment method for a subsector of Lisbon's city centre, known as Baixa Pombalina. The study employed an index-based method to analyse the vulnerability of ordinary unreinforced masonry (URM) structures, highlighting the significance of historical urban areas in risk assessment and mitigation (Arrighi et al, 2023).…”

“…In an urban risk assessment method, a crucial phase in predicting possible losses is to develop an exposure model for all assets that may be subject to hazards, such as people, properties, and economic activities. Buildings, in particular, require the identification of their position and monetary value; hence, the exposure model serves also as a geographical data layer for risk assessment (Arrighi et al, 2023;Sterlacchini et al, 2014). In this study, only ordinary unreinforced masonry (URM) structures were identified, classified, and structured into an inventory containing the most essential building attributes.…”

Planning for More Resilient and Safer Cities: A New Methodology for Seismic Risk Assessment at the Urban Scale, Applied to a Case Study in Italy

“…Earthquakes, as other natural hazards, are natural phenomena occurring worldwide, whose associated consequences pose serious threats to natural and man-made environments [1][2][3]. The disruptive energy of an earthquake can harm people, cause severe property damages, damage infrastructures and facilities, and cause monetary losses.…”

A Multidisciplinary Approach for the Vulnerability Assessment of a Venetian Historic Palace: High Water Phenomena and Climate Change Effects

“…Reflecting on the future of historic centers and finding strategies for their conservation and protection has become a crucial issue all over the world nowadays, also in view of the new threats represented by climatic change. In this field, it is fundamental to develop tools to support decision-makers and technicians to face this complex problem, and also in the framework of multi-risk approaches, e.g., [1][2][3][4][5]. For this aim, the available technologies and innovations may make a significant contribution, as an example, within structural assessment [6][7][8][9].…”