A multi-hazard assessment approach to reveal and compare heat- and flood-related risks and inequalities in London, Boston, and Sydney

Abstract

Climate hazards pose several challenges to cities and their inhabitants, especially the more vulnerable ones, calling for a systematic adoption of adaptation measures. Climate risk assessments are of undoubtful importance to investigate and comprehend the nature of climate-related risks, and can ideally support adaptation planning through the identification of risk hotspots. In this study, a replicable method for assessing population risk to be negatively affected by heat stress and (river and coastal) flooding is proposed, providing a tool to support risk-based adaptive planning. Through a novel multi-hazard and multi-metric perspective and a comparative approach to reveal how they perform in terms of climate justice, the method is applied in three major cities: London, UK; Boston, US; Sydney, Australia. Results show the intra-city risk spatial variability, together with the factors that, with different magnitudes, contribute to the final risk condition. Boston has the highest proportion of population living in the most at-risk areas for heat stress. The same applies to London concerning flood risk. Sydney has the lowest shares for both. Boston and London also show greater problems of uneven distribution of risk, with the low-income residents more likely living in the riskiest areas, especially regarding heat stress. While replicability in other contexts depends on data availability, the method and its metrics are flexible to be adjusted according to different typologies of input data. The use of assessments of this type may in principle support decisions that prioritize interventions in areas where more disadvantaged people live, thus theoretically alleviating intra-city inequalities. However, proper planning and monitoring are needed to avoid reverse effects, such as gentrification processes that could lead to exacerbating existing or creating new injustices.