The changing city: risk and built heritage. The case of Lisbon downtown

摘要

After the devastating earthquake, tsunami and fires of 1755, the city of Lisbon was rebuilt as a modern disaster resilient city, implementing strict planning controls and earthquake resistant construction technologies. This is reflected in the regular grid layout of the historic city, namely the Baixa Pombalina, and its built fabric. But the city has changed considerably since 1755. Through GIS mapping of the city, this study identifies the exposure of the built heritage of Lisbon Downtown to natural hazards including earthquake, tsunami, flood and landslide. It then highlights some of the changes that have occurred within the city's landscape since 1755 and the potential impacts that these may have had on the ability of the city's fabric to perform as designed. In particular, it focuses on the historic urban precinct of Baixa Pombalina, the heart of the rebuilt city and part of the tentative UNESCO World Heritage property of Lisbon. Although many studies have been undertaken to examine the seismic performance of the Pombaline buildings, few have examined the greater context in which the buildings exist and its potential impact on their performance. Will the buildings be able to withstand a similar event now or have they been compromised by the changes that have occurred in and around them? This study considers the vulnerability of the city's historic structures and sites to various hazards and identifies areas of further research needed to enable the development of appropriate mitigation strategies to strengthen the resilience of the historic city.