Development of Next-Generation Flood Inundation Maps: A Case Study in Kaohsiung City, Taiwan

Abstract

Flood inundation mapping has become a critical reference for flood risk management, particularly for determining insurance premiums and formulating mitigation strategies in rapidly urbanizing areas with high population density. With recent advancements in mapping technologies and high computing capacity, high-resolution spatiotemporal datasets can be integrated into flood simulation models. In this study, a hydrological digital elevation model (HyDEM) was implemented at the city scale for Kaohsiung City, Taiwan, to improve urban flood simulations. The HyDEM incorporated specialized datasets, including high-resolution DEM, building layer, bankline layer, and seadike layer. Using the Delft3D FM 1D-2D modeling platform, 10 basin-scale models were constructed across Kaohsiung City, and multiresolution computational meshes were employed to achieve a balance between simulation accuracy and computational efficiency. Model performance was validated using two historical flood events, during which it achieved an overall accuracy of similar to 84% for the June 5 Rainstorm event and 80% for the Typhoon Gaemi (2024) event. These results indicate that flood inundation maps (FIMs) can be considerably improved by preserving critical topographic features, particularly building footprints and hydraulic structures such as river and sea dikes. The proposed method thus addresses limitations of earlier generations of FIMs and provides a framework for advancing next-generation flood inundation maps.