This study investigates the short- and long-run impact on population dynamics of the major flood in the Netherlands in 1953. A dynamic difference-in-differences analysis reveals that the flood had an immediate negative impact on population growth, but limited long-term effects. In contrast, the resulting flood protection program (Deltaworks), had a persisting positive effect on population growth. As a result, there has been an increase in population in flood-prone areas. Our results suggest a moral hazard effect of flood mitigation leading to more people locating in flood-prone areas, increasing potential disaster costs.