Are we safer than before from flooding?

Abstract

The paper aimed to better characterize how flood impacts have changed over time in Japan. It is hypothesized that different flood impact indicators vary in their sensitivity to significant changes. To test this hypothesis, change-point analysis was applied to various indicators, including flood-related deaths, the ratio of deaths to total flood victims, and a newly proposed composite indicator that integrates both loss of life and property damage. The analysis revealed that while the annual number of flood victims has remained statistically unchanged during the study period, the proportion of deaths among victims has increased. Similarly, although the annual number of completely damaged houses did not show a significant change, the proportion of completely damaged houses relative to the total number of flooded houses has risen. According to the newly developed composite indicator, the overall impact of flooding in Japan has shifted upward since 2004. The value of this study lies in its novel approach of combining loss of life with property damage in trend analysis, enabling policymakers and citizens to better understand the evolving risks posed by floods. These findings not only provide policymakers with a comprehensive reference for evaluating the effectiveness of flood management measures but also help promote public participation in flood mitigation efforts.

Keywords

citizen / change-point / flood impact / house damage / indicator / life loss

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RIGHTS & PERMISSIONS

2025 The Author(s). River published by Wiley-VCH GmbH on behalf of China Institute of Water Resources and Hydropower Research (IWHR).