Development of flood hazard index under climate change scenarios in Java Island

Climate change-induced alterations in temperature and precipitation patterns pose a significant threat to flood risk worldwide. This research focuses on Java Island and presents a method to develop a flood hazard index map considering various future climate change scenarios. To simulate flood characteristics for various scenarios, an RRI (Rainfall-Runoff-Inundation) model was calibrated and validated using six different flood events in three basin areas. Furthermore, the baseline, historical 100-year return period, was compared against climate change scenarios representing near-future (2015–2060) and far-future (2061–2100) cycles, integrating six bias-corrected climate models under the SSP2.45 and SSP5.85 scenarios. This study reveals that the maximum predicted flood extents under both SSP2.45 and SSP5.85 scenarios surpass the baseline across all cycles, with propagation areas expanding with each scenario and cycle. Notably, the worst-case hazard score for all cycles and scenarios occurred in DKI Jakarta and Central Java due to high rainfall concentration and population density. In the case of DKI Jakarta, the hazard score was between 0.61 and 0.76, while, for Central Java, the hazard score was between 0.61 and 0.73. These findings are important for guiding non-governmental and governmental institutions in making robust flood mitigation policies to safeguard vulnerable communities in Java Island.