The long-run population effects of floods in Spanish municipalities, 1877–2011

This paper analyzes the long-term effects of floods on urban areas in Spain, focusing on demographic impacts across municipalities from 1877 to 2011. By combining historical data on flood events and municipal population sizes, the study utilizes advanced difference-in-differences estimation methods, specifically the approach developed by Callaway and Sant’Anna (2021), which accounts for varying treatment timings and heterogeneous effects. The results reveal that floods only have significant and lasting demographic impacts when they involve casualties. In such severe cases, the devastation drives residents to relocate to other areas, amplifying depopulation trends and fostering heightened awareness of flood risks among the affected population. These findings align with theories of increasing returns and random growth, suggesting that while minor natural disasters tend to have temporary effects on urban structures, severe events can alter long-term demographic trajectories. Furthermore, the study highlights the importance of considering geographical and spatial factors to ensure robust estimates. The psychological impact of catastrophic events, as documented in behavioral economics, underscores the need for effective mitigation strategies. In addition to traditional flood protection measures like dikes and dams, the research emphasizes improving flood risk maps, better identifying flood-prone areas, and strengthening flood alert systems. Moreover, effective communication of these alerts is critical to minimizing loss of life and mitigating long-term impacts. These measures, coupled with public assistance for affected individuals, could enhance resilience and ensure more balanced urban planning in flood-prone regions.