Mapping global floodplain development disparities highlights drivers behind intensifying flood losses

Floodplains attract disproportionate concentrations of population and economic activity globally, yet the systemic flood risks emerging from this uneven development remain insufficiently characterized. Through a global analysis spanning 2000-2020, we quantify floodplain development patterns and associated flood losses across nations with varying socio-economic statuses and flood protection levels. Our results reveal that floodplains have experienced faster growth than non-floodplains in both population density and GDP density. These trends show significant variation depending on income and flood protection levels, revealing a divergent risk pattern: wealthier, well-protected nations accumulate greater economic assets at risk, whereas poorer, under-protected nations concentrate larger populations at risk. Furthermore, the sensitivity of flood-induced economic damages to floodplain GDP growth is more pronounced in wealthier nations, whereas the sensitivity of flood-induced fatalities to floodplain population growth is higher in poorer nations. This underscores the distinct economic vulnerability of developed nations and the human vulnerability of developing nations in the face of flooding. Based on these findings, we argue for prioritizing economic resilience and the decoupling of economic development from flood-prone asset accumulation in higher-income nations, while simultaneously emphasizing humanitarian protection and equitable infrastructure investment in lower-income nations.