Conference Agenda

Frequent urban inundations from changing rainfall patterns highlight the need for reliable, timely flood forecasting. This study evaluates inundation prediction under varying storm sewer network simplification and surface grid resolutions using InfoWorks ICM, which supports 1D–2D coupled simulations. Five storm sewer configurations, determined by cumulative watershed area, and five grid resolutions yielded 25 scenarios. Results show that the number of two-dimensional mesh elements influences simulation time more than the number of storm sewer pipes. Coarser grids significantly reduce computation but may oversimplify topographic variability, reducing inundation depths and overestimating inundation extents. Conversely, increasing network detail raises inundation area and depth as well as computation time. For small- and medium-scale basins (e.g., Sinlim4, Daelim), a simplification threshold of 2.25 ha was optimal, while for large basins, 1 ha was best. These thresholds strike a balance between modeling accuracy and simulation speed. Overall, the study underscores the importance of jointly optimizing surface grid resolution and storm sewer network complexity to enhance the accuracy and efficiency of urban inundation forecasting.