Population versus Building Exposure in Flood Risk Assessment

Flood risk management commonly relies on structural exposure assessments, with a strong emphasis on the built environment. However, the relationship between exposure and observed flood impacts, such as economic losses, remains uncertain. In particular, the role of population exposure in explaining flood impacts is often underrepresented in large-scale risk assessments.

This study presents an integrated national-scale analysis of flood exposure in Sweden, explicitly comparing the explanatory power of population-based and building-based exposure metrics across two flood hazard scenarios. Using high-resolution geospatial datasets combined with empirical insurance claims data, flood exposure for buildings and populations was quantified and analyzed at municipal and regional scales.

The results show that population exposure exhibits a stronger relationship with observed flood impacts than building exposure, particularly under more severe flood scenarios. Economic losses, represented by total insurance compensation, were better explained by population-based exposure metrics than by structural exposure alone. These findings highlight the importance of human occupancy patterns and dynamic population distributions in shaping flood impacts.

Overall, the study demonstrates that integrating population exposure into flood risk assessments provides more robust insights into observed flood losses, supporting improved risk-informed decision-making, preparedness planning, and resilient flood risk management strategies.