Validation of a social vulnerability index in context to river-floods in Germany

Social vulnerability indices are a means for generating information about people potentially affected by disasters that are e. g. triggered by river-floods. The purpose behind such an index is in this study the development and the validation of a social vulnerability map of population characteristics towards river-floods covering all counties in Germany. This map is based on a composite index of three main indicators for social vulnerability in Germany - fragility, socio-economic conditions and region. These indicators have been identified by a factor analysis of selected demographic variables obtained from federal statistical offices. Therefore, these indicators can be updated annually based on a reliable data source. The vulnerability patterns detected by the factor analysis are verified by using an independent second data set. The interpretation of the second data set shows that vulnerability is revealed by a real extreme flood event and demonstrates that the patterns of the presumed vulnerability match the observations of a real event. It comprises a survey of flood-affected households in three federal states. By using logistic regression, it is demonstrated that the theoretically presumed indications of vulnerability are correct and that the indicators are valid. It is shown that indeed certain social groups like the elderly, the financially weak or the urban residents are higher risk groups.