Extreme climate and land subsidence: flood vulnerability projection in the Bandung Basin by 2045 and its socio-economic implications

Abstract Background Flood is one of the most frequent disaster events in Indonesia and has a strong correlation with local climate conditions. In addition, land subsidence can increase the extent of flood-prone areas in the future. Understanding future flood risk is therefore essential for planning and mitigation decisions. This study predicts flood-prone and risk areas around the Bandung Basin in 2045 by integrating land subsidence and a flood-prone modeling approach. Land subsidence is observed using Sentinel-1 and projected to a future Digital Elevation Model. In the flood modeling, predicted land use/land cover change is also incorporated as an input to the model. Results The results show that future land subsidence is projected to increase most notably in densely populated and rural areas. Changes in the elevation indicate the emergence of new flood points, especially in road and settlement areas. Bandung Regency and West Bandung record the highest subsidence rates, at 0.223 and 0.22 m per year, respectively. Second, the land use/land cover predictions reveal a significant expansion of built-up areas. From 2005 to 2045, built-up areas increase by 6.52%, reflecting rapid urbanization growth across the Bandung Raya region. Finally, future flood simulations indicate that although the total inundation area tends to decrease from 2025 to 2045, the proportion of high-depth inundation (> 1.5 m) increases. This pattern is driven by progressive land subsidence, which deepens ground elevation depression over time, causing areas that were previously less affected to subside further. As subsidence progresses, flood-prone zones become more localized: the flood footprint contracts, while flood water depths increase in subsided hotspots. Conclusions Overall, these findings provide a policy foundation for prioritizing areas affected by land subsidence and strengthening flood damage mitigation efforts. The study is expected to contribute to Sustainable Development Goals 13 and 15, particularly through climate action and protection of terrestrial ecosystems for future flood disaster mitigation.