Multi-hazard conditions in urban settlements: a framework for heatwave and flooding integrated impacts assessment to support climate-oriented design

The co-presence and the simultaneous occurrence of multi-hazard conditions can trigger the attainment of tipping points, potentially responsible for undermining the balance of urban settlements. In recent years, there has been a growing awareness of the need to know, investigate and to manage multiple risks involving impacts on assets, resources and people. The analysis of potential impacts can be based on a spatial approach that considers a base area and the hazards that may occur within this area (including cascade, compound, effects, etc.).

In relation to multi-hazard conditions – which may vary both temporally and spatially – urban hot spots can be identified as areas where the consequences of the combination of vulnerability, exposure and hazard are condensed as transition factors from risk conditions to impacts.  

In this scenario, the contribution aims to test a decision support framework – based on a systemic approach - for climate adaptation and mitigation design strategies and solutions under multi-hazard conditions.

The methodological approach is based on the identification of urban hotspots based on climate-related impacts. The proposed process identifies urban hotspots evaluating the impacts resulting from heat wave and pluvial flooding, assuming as exposed value the total population potentially subject to suffer the negative impacts of extreme climatic events.

The evaluation of an integrated impact indicator considers the intrinsic features of the urban system and the hazardous phenomena to understand the complex effects that emerge from the coexistence of multiple risk on the same area and the same exposed assets. The areas where the impact values of heat wave and pluvial flooding are higher and, therefore the integrated impact value is increased, represent urban hotspot. The criticality, thus assessed, is based on a complex data set that includes both exposure, i.e. the population that is likely to be affected, and vulnerability, determined by the physical characteristics of the urban system considered.

Based on the knowledge phase, it is then possible to operate simulations of adaptation and mitigation strategies and solutions, supporting decision-makers in evaluating design alternatives for increasing resilience and reduce urban risks.

The framework, developed in a GIS environment, serves as a simplified tool for assessing the resilience of project proposals – through the application of the Proof of Concept (PoC) process – aimed at counteracting impacts under multi-hazard climate conditions, contributing to guide the development of policies, plans and projects. The use of the PoC methodological approach allowed the introduction of some innovative elements that contribute to the usefulness of the proposed decision-making model. A testing case in the city of Naples is proposed; where the PoC plays a significant role to identify and address the challenges and limitations that may arise in the early stages of developing an idea or project.

The contribution is developed within the research Partenariato Esteso PE3, RETURN project (multi-Risk sciEnce for resilienT commUnities undeR a changiNg climate) (Codice Progetto MUR: PE00000005), in the framework of the Spoke TS1 - Urban and metropolitan settlements activities.