Flood vulnerability indices at varying spatial scales

Populations around the world are vulnerable to natural disasters. Such disasters are occurring with increased frequency as a consequence of socio-economic and land-use developments and due to increased climate variability. This paper describes a methodology for using indicators to compute a Flood Vulnerability Index which is aimed at assessing the conditions which influence flood damage at various spatial scales: river basin, sub-catchment and urban area. The methodology developed distinguishes different characteristics at each identified spatial scale, thus allowing a more in-depth analysis and interpretation of local indicators. This also pinpoints local hotspots of flood vulnerability. The final results are presented by means of a standardised number, ranging from 0 to 1, which symbolises comparatively low or high flood vulnerability between the various spatial scales. The Flood Vulnerability Index can be used by international river basin organisations to identify and develop action plans to deal with floods and flooding or on smaller scales to improve local decision-making processes by selecting measures to reduce vulnerability at local and regional levels. In this work the methodology has been applied to various case studies at different spatial scales. This leads to some interesting observations on how flood vulnerability can be reflected by quantifiable indicators across scales, e. g. the relationship between the flood vulnerability of a sub-catchment with its river basin or the weak relation between the flood vulnerability of an urban area with the sub-catchment or river basin which it belongs to.