An advanced methodology for the multi-risk assessment : an application for climate change impacts in the North Adriatic case study (Italy)

Abstract

Climate change will pose multiple impacts on natural and human systems worldwide, increasing risks from long-term climate trends and disasters triggered by weather extremes. Till now, a hazard by hazard approach was considered in risk assessment for evaluating the consequences of individual natural and climate-related hazards (e.g. heavy precipitation events, droughts, floods, debris flows, landslides, storm surges) on vulnerable systems, without any consideration of an integrated assessment of multiple risks triggered by different forces. Starting from an initial review of existing multi-risk assessment concepts and tools applied by international organisations and projects, the main aim of the thesis was to develop and apply an advanced and interdisciplinary multi-risk methodology, allowing a sound assessment and communication of the multi-faceted threats posed by a variety of climate-related hazards across regions and sectors. A multi-hazard assessment was developed to analyze the relationships of multiple hazards (e.g. sea-level rise, coastal erosion, storm surge) happening in the same spatial and temporal area, using an influence matrix and the disjoint probability. Then, the multi-vulnerability of different exposed receptors (e.g. natural systems, beaches, agricultural and urban areas) was estimated trough a variety of vulnerability indicators (e.g. vegetation cover, sediment budget, % of urbanization) associated to different hazards. Finally, the multi-risk assessment was performed by integrating the multi-hazard with the multi-vulnerability index for the exposed receptors, thus supporting the development of information useful to stakeholders in the definition of adaptation strategies. The methodology was tested in the North Adriatic coast producing GIS-based multi-hazard, exposure, multi-vulnerability and multi-risk maps. The results of the analysis showed that the areas affected by higher multi-hazard scores are located close to the coastline where all the investigated hazards are present. Multi-vulnerability assumes relatively high scores in the whole case study, showing that beaches, wetlands, protected areas and river mouths are the more sensible targets. Finally, the multi-risk map presents a similar trend of the multi-hazard map, highlighting beaches as the receptor more affected by multi-risk with a relevant percentage of surface (i.e. 60%) in the very high and high multi-risk classes. The final estimate of multi-risk for coastal municipalities provides useful information for local public authorities to set future priorities for adaptation and define future plans for shoreline and coastal management in view of climate change. In conclusion, the proposed multi-risk methodology is a step forward to traditional single risk assessments, providing a more comprehensive – even if relative - assessment of the multiple impacts and risks affecting the same area. Moreover, moving from the multi-risk methodologies generally developed for natural hazards, the presented methodology considers also future scenarios of climate-related hazards, providing a generic guideline for its application to different case studies, scale of analysis and contexts. The proposed multi-risk methodology can be applied adopting a bottom-up approach considering stakeholder needs in order to obtain tailored risk-based adaptation services suitable to mainstream adaptation in the development of plans, policies and programmes.