Impact Assessment for Climate Change in the Midori River Basin with Large Ensemble Climate Simulation Data

The aims of this study are to assess a future change of heavy rainfall caused by climate change and to propose an evaluation method for quantitatively evaluating flood frequency by using of d4PDF, a large ensemble climate projection dataset. In recent years, the effects of climate change have become apparent, such as a rise in temperature, an increase in the frequency of flood. In Japan, record-breaking heavy rain caused extensive damage along a river basin year after year, e.g. the heavy rainfall event of July 2017 in Kyushu Hokubu, the heavy rainfall event of July 2018. Rainfall is expected to become more intense because global warming has boosted the number of record-breaking rainfall events.

In order to protect people’s lives and property under climate change, it is necessary to take adaptation measure to prevent or reduce damage expected in the future. Planning of adaptation for climate change will be based on assessments of disasters caused by extreme events. A large ensemble of climate simulations with high-resolution atmospheric models is useful. The results of these simulations, named d4PDF, are now being used in various impact assessment studies for natural disasters. In this study, the annual maximum rainfall events were extracted from the large ensemble database “d4PDF”. And then, we examined spatiotemporal characteristics of basin-averaged rainfall in the Midori River basin. Furthermore, flood runoff analysis were conducted to examine a quantity of discharge expected under global warming.