County-scale flood risk assessment of properties and associated population in the United States

Flood risk was assessed at the county scale in the United States, focusing on properties and associated populations. The assessment of risk was conducted using the Intergovernmental Panel on Climate Change (IPCC) framework, which incorporates hazard, exposure, and vulnerability as integral components. Additionally, the response was added as a core component to the flood risk framework. A Self-Organizing Map (SOM) was implemented to carry out unsupervised clustering, which captured the interactions within vulnerability and overall risk components. The results indicate that counties in the eastern and southern regions of the United States, along with those in the coastal areas, face a heightened risk. This is primarily due to a larger population and a more significant concentration of properties with high hazard scores. However, our analysis also showed that the counties in these regions have very robust responses, including structural, non-structural, and emergency measures, subduing the risk associated with flooding. We also compared our maps with the National Risk Index (NRI), revealing a reasonable correlation between the Social Vulnerability Index (SoVI) and our vulnerability assessment. A notable distinction between the SoVI and our proposed vulnerability framework was our inclusion of unique vulnerability indicators referring to social, ecological, economic, and health factors specific to flooding, suggesting that vulnerability can vary depending on the type of natural hazard. A county-scale approach like this will make policymakers aware of the existing flood risks, which can help make tailored, effective, and locally relevant policies.