2025 Volume 81 Issue 16 Article ID: 24-16073
In recent years, water-related disasters have become more severe and frequent due to climate change. Additionally, there is concern about the occurrence of a massive tsunami caused by the Nankai Trough earthquake, which has a 70-80% probability of occurring within the next 30 years. Therefore, it is necessary to consider the combined disasters of tsunamis and floods. In this study, we used a comprehensive flood analysis model to examine the characteristics of tsunami run-up during compound disasters for the Asahi River, Hyakken River, and Yoshii River, which flow into Kojima Bay. The results confirmed that tsunamis run up the rivers for several kilometers more significantly when the scale of the flood is small. Conversely, when the scale of the flood increases, the run-up distance of the tsunami decreases, but the river water level rises due to the flood itself. Additionally, rivers with a larger incidence angle of the river mouth relative to the tsunami propagation direction in the sea tend to show a more pronounced effect of flood flow, leading to a narrower range of water level rise.
