Ralph Allen Acierto, Toshio Koike, Tomoki Ushiyama, Yozo Tanaka, Keijiro Kubota
Received 20 January, 2025
Accepted 8 April, 2025
Published online 9 August, 2025

Ralph Allen Acierto¹⁾, Toshio Koike¹⁾, Tomoki Ushiyama¹⁾, Yozo Tanaka¹⁾, Keijiro Kubota¹⁾

1) International Centre for Water Hazard and Risk Management (ICHARM), Public Works Research Institute (PWRI), Japan

Due to the increasing frequency and intensity of heavy rainfall events observed globally, the impact of climate change on critical heavy rainfall information, such as probable maximum precipitation (PMP), requires urgent update to ensure its utility in protecting lives and informing infrastructure design.

We applied the depth-area-duration (DAD) analysis on a 5-km d4PDF large ensemble dataset under historical and warming scenarios (+2K, +4K) with 720-year climate periods to investigate climate change impacts on PMP using the change factor approach. Annual Maximum Rainfall (AMR) in different durations over Northwest (NW) and Southeast (SE) Kyushu were analyzed. Depth-area relationships were derived and enveloped to estimate DAD-based PMP. Change factors were calculated as the ratio of warming scenario PMP to historical PMP.

Results indicate that AMR magnitude increases in NW Kyushu by approximately 10% at +2K and 20% at +4K across all durations. In SE Kyushu, it increases approximately 10% overall, with a larger increase (10–20%) above the 75th percentile. PMP change factors were higher in NW Kyushu (1.17 at +2K, 1.28 at +4K) compared to SE Kyushu (1.12 at +2K, 1.22 at +4K). These estimates highlight the need to address climate change impact on PMP used for flood risk management.

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Copyright (c) 2025 The Author(s) CC-BY 4.0