[H-CG22] Adaptation to climate change and its social implementation

[HCG22-04] Flood Risk Assessment by Atmospheric Rivers

*Shamoto Akihiro¹, Koji Dairaku², Paul Ayodele Adigun¹, Defersha Dessalew Tadesse¹, ALYSSA GEWELL AGENA¹ (1.University of Tsukuba, 2.University of Tukuba)

Keywords:Flood Risk, Atmospheric rivers , Japan

In recent years, extreme rainfall has occurred frequently in Japan, and recent studies have indicated that atmospheric rivers detected in Japan contribute significantly to these heavy rainfall events. Although previous studies have focused on the relationship between atmospheric rivers and extreme events, analyzing the relationship between them and the damage they cause is useful for taking appropriate measures to mitigate their social impacts. Therefore, this study uses comprehensive atmospheric reanalysis data and flood damage records for 47 years (1962-2008) to assess atmospheric rivers and their social impacts in Japan. The results of an analysis of the relationship between the presence of atmospheric rivers and the probability of flooding in each grid in Japan showed that the likelihood of flooding increased with the presence of atmospheric rivers at all sites in Japan, and this increase was particularly pronounced on the Sea of Japan side. Then, comparing the average number of damages and the average area inundated when the atmospheric river was present and when it was absent, the average number of damages and the average area increased by about 2.5 times and 2.9 times, respectively. The result that the ratio of the area inundated by the presence of atmospheric rivers is higher than the ratio of the number of damages by the presence of atmospheric rivers indicates that the presence of atmospheric rivers increased the average area inundated by flooding. This result is statistically significant. A study of factors influencing the occurrence and damage of flooding showed that an increase in the maximum IVT and duration of atmospheric rivers tends to increase the occurrence of flooding, the area inundated, and the amount of damage. These results suggests that intense atmospheric rivers may increase the risk of flooding. These results indicate that atmospheric rivers are detecting and causing damage on the west coasts of North America, Europe, South Asia, and Japan. Therefore, based on the findings of this study, the presence and intensity of atmospheric rivers increase the probability of flooding. The results of this study contribute to our understanding of the economic impacts of atmospheric rivers in Japan.