Author(s): Nguyen Thanh Thu; Makoto Nakatsugawa; Tomohito Yamada; Tsuyoshi Hoshino
Linked Author(s):
Keywords: Flood risk; D4PDF; IFAS; River discharge; Climate change
Abstract: This study evaluated the flood risk of the Ishikari River basin under various climate change scenarios by using a large-ensemble dataset (d4PDF) with a high resolution of 5km. The top 20 and the top 36 rainfall events (corresponding to a return period of 150 years for the historical and future simulations, respectively) were selected. The Integrated Flood Analysis System (IFAS) was applied to simulate the flood risk under climate change scenarios after calibration and validation with observed discharge. After validation, we used the rainfall data from a large-ensemble dataset (d4PDF) as input to the IFAS model to assess the future flood risk. We found that the flood risk is expected to increase due to increases in rainfall for both historical and future simulations in the target basin. Moreover, the year of maximum rainfall (372 mm/72hr) does not agree with the year of greatest discharge of 17,982 m3/s under the historical simulation. In the future simulation, we obtained two cases with the same maximum rainfall amount (454 mm/72hr), but the peak discharges differed (30,018 m3/s versus 22,444 m3/s, respectively). This shows that the ranking of rainfall for a certain event does not necessarily coincide with the peak discharge ranking. As a result, river discharge volume depends not only on the total rainfall, but also on the temporal and spatial rainfall distribution. These results of this study will be helpful in developing flood disaster prevention plans in the target basin.
Year: 2020