FUTURE CHANGES OF COOCCURRENCE PROBABILITY OF EXTREME FLOODS USING BIVARIATE EXTREME VALUE THEORY AND d4PDF

Abstract

 We applied the bivariate extreme value theory to d4PDF 4-degree rise experiment in the Kanto and Kyushu regions and the metropolitan areas and analyzed the future change of cooccurrence probability of floods over the design level (extreme floods). Its return period in the 4-degree rise scenario was estimated as 800 years in Kanto and 473 years in Kyushu which is similar to the past experiment, indicating that future changes in extreme floods will be caused by enhanced frequency of extreme floods in each river system. That between the Ara and Shonai Rivers was obtained as 4,000 years by non-parametric estimation while parametric estimation was unstable; therefore, further ensemble enrichment or meteorological analysis is crusial for more robust estimation.