Construction of an Integrated Social Vulnerability Index in urban areas prone to flash flooding

Abstract

Abstract. Flash floods are considered to be one of the natural hazards with the greatest capacity to generate risk. Therefore, a change in traditional flood risk management (FRM) is necessary towards an integrated approach, which requires a comprehensive assessment of the social risk component. In this regard, integrated social vulnerability (ISV) gives us the spatial distribution, contribution and combined effect of exposure, sensitivity and resilience to the total vulnerability, although these components are often disregarded. ISV is characterized by the demographic and socioeconomic characteristics that condition a population's capacity to cope with, resist and recover from risk, and it can be derived from assessing the Integrated Social Vulnerability Index (ISVI). As far as we know, it has not yet provided a methodological approach to construct the ISVI in urban areas of Castilla y León (northern central Spain, 94,223 km2, 2,478,376 inhabitants) prone to flash flooding. A hierarchical segmentation analysis (HSA) was performed prior to the principal components analysis (PCA), which helped to overcome sample size limitation inherent to PCA. ISVI was obtained from weighting vulnerability factors based on the tolerance statistic. Additionally, latent class cluster analysis (LCCA) was accomplished aiming to identify vulnerability spatial patterns within the study area. Our results show that the ISVI has high spatial variability. Moreover, the LCCA allowed us to identify the source of vulnerability in each urban area cluster. These findings enable a tailored design of FRM strategies, which intends to increase the efficiency of plans and policies, helping reduce implementation costs for mitigation measures.