An Empirical Social Vulnerability Map for Flood Risk Assessment at Global Scale ("GlobE-SoVI")

Fatalities caused by natural hazards are driven not only by population exposure, but also by their vulnerability to these events, determined by intersecting characteristics such as education, age and income. Empirical evidence of the drivers of social vulnerability, however, is limited due to a lack of relevant data, in particular on a global scale. Consequently, existing global-scale risk assessments rarely account for social vulnerability. To address this gap, we estimate regression models that predict fatalities caused by past flooding events (n = 913) based on potential social vulnerability drivers. Analyzing 47 variables calculated from publicly available spatial data sets, we establish five statistically significant vulnerability variables: mean years of schooling; share of elderly; gender income gap; rural settlements; and walking time to nearest healthcare facility. We use the regression coefficients as weights to calculate the "Global-Empirical Social Vulnerability Index (GlobE-SoVI)" at a spatial resolution of similar to 1 km. We find distinct spatial patterns of vulnerability within and across countries, with low GlobE-SoVI scores (i.e., 1-2) in for example, Northern America, northern Europe, and Australia; and high scores (i.e., 9-10) in for example, northern Africa, the Middle East, and southern Asia. Globally, education has the highest relative contribution to vulnerability (roughly 58%), acting as a driver that reduces vulnerability; all other drivers increase vulnerability, with the gender income gap contributing similar to 24% and the elderly another 11%. Due to its empirical foundation, the GlobE-SoVI advances our understanding of social vulnerability drivers at global scale and can be used for global (flood) risk assessments. Social vulnerability is rarely accounted for in global-scale risk assessments. We develop an empirical social vulnerability map ("GlobE-SoVI") based on five key drivers of social vulnerability to flooding, that is, education, elderly, income inequality, rural settlements and travel time to healthcare, which we establish based on flood fatalities caused by past flooding events. Globally, we find education to have a high and reducing effect on social vulnerability, while all other drivers increase vulnerability. Integrating social vulnerability in global-scale (flood) risk assessments can help inform global policy frameworks that aim to reduce risks posed by natural hazards and climate change as well as to foster more equitable development globally. We develop a global map of social vulnerability at similar to 1 km spatial resolution based on five key vulnerability drivers ("GlobE-SoVI") We establish vulnerability drivers empirically based on their contribution to predicting fatalities caused by past flooding events Accounting for social vulnerability in global-scale (flood) risk assessments can inform global policy frameworks that aim to reduce risk