Author(s): Hisanori Kusuhara; Kohji Tanaka; Ryoukei Azuma
Linked Author(s): Ryokei Azuma
Keywords: Global warming projection spatial resolution frequency simultaneous occurrence
Abstract: Recent years have seen unusually heavy rains and powerful typhoons, resulting in frequent water-related disasters throughout Japan. In response to this increase in external meteorological forces, many risk assessment studies have been conducted using global warming prediction values (d4PDF; 20km resolution). Recently, a higher resolution version with a resolution of 5km has been published, which can be applied to future projections for tributary river basins. In this study, the Kumano River basin of the Shingu River system, which has many cases of flood damage, was targeted. When considering future forecast data for the main river basin and tributary river basins, it is necessary to understand the hydrological characteristics of the different spatial resolutions. In this study, we aimed to understand the future rainfall and runoff frequency and the tendency of simultaneous occurrence of the main and branch rivers at different resolutions (20km and 5km) of the warming forecast data. The results showed that rainfall and runoff at 20km resolution tended to be underestimated compared to those at 5km resolution. The rainfall at 20km was underestimated compared to that at 5km, and the rainfall at 5km was underestimated at the same time, suggesting that 5km is appropriate for future projections in this basin. The actual frequency of coincident occurrences of the main branch river in the warming projection was confirmed to be extremely rare regardless of the resolution.
Year: 2025