Estimation of Future 100-year Precipitation in Mie Prefecture, Japan

Probabilistic precipitation, such as the 100-year rainfall, is widely used as the design storm for planning flood control structures. However, due to climate change, the return periods estimated 50 years ago are no longer valid. This shift necessitates a fundamental reconsideration of how we determine design levels for construction. In other words, there is an urgent need for more sophisticated methodologies capable of handling non-stationary precipitation data.

To address these challenges, we present two key topics:

• In Japan, the national and local governments have issued guidelines suggesting that future extreme rainfall intensities can be estimated by multiplying present-day values by a change factor of 1.1 to 1.15, assuming a 2.0°C increase in global temperature. While these guidelines tend to treat the change factor as largely uniform across regions for practical simplicity, we contend that it should be estimated with greater geographical precision. Consequently, we estimated the change factors specifically for Mie Prefecture in central Japan. Our results demonstrate that even within a single prefecture, the factor varies significantly depending on the specific location.

• We have been developing a novel approach to estimate future 100-year precipitation levels through multivariate analysis. The details of this methodology and our findings will be presented in our poster session.