ANALYZING FUTURE CHANGES OF EXTREME RIVER DISCHARGE IN JAPAN USING d4PDF

Abstract

 This study estimated future changes in extreme river discharge in all the class-A rivers in Japan using d4PDF. A distributed rainfall-runoff model was constructed for all the rivers accounting flood control of major dams. A novel bias correction method was developed and applied to the annual maxima of basin rainfall in d4PDF with thousand-year data using the Radar AMeDAS Rainfall. As the results, the simulated river discharges corresponding to the return period of design rainfall are in good agreement with design flood discharges. Extreme flood discharge will increase in all the rivers, especially in the Kanto region and the Pacific side of the Hokkaido, Tohoku and Kyushu regions. Rainfall-runoff simulation with/without dam operation in the Oyodo River basin indicated that its dam control effect for peak discharge remains for around 1000-year flood in the past experiment. Such floods will occur once in 100 years in the 4-degree rise experiment; consequently, the dam control may become less effective for events over a 100-year flood.