By taking the North Bund area in Shanghai’s Hongkou District, the core built-up area, as the study region, a 1D-2D coupled model integrating pipe network topology optimization and surface micro-topography refinement was developed to precisely simulate rainstorm waterlogging processes in urban high-density areas. The model’s reliability and applicability were dynamically validated using multiple recorded storm events from 2020 to 2024. Based on this model, two drainage system optimization schemes for the North Bund area were evaluated (Scheme 1: adding new main stormwater pipelines + upgrading the riverside pumping station; Scheme 2: retrofitting main pipelines + enhancing the efficiency of existing pumping stations). Results indicate that the constructed 1D-2D coupled model accurately simulates rainstorm waterlogging processes in urban high-density areas under various rainfall conditions. Under the design rainstorm scenario with a 10-year return period, Scheme 1 achieves a 52.5% reduction in overflow nodes and a 44.6% decrease in inundated area, demonstrating superior system resilience compared to Scheme 2 (47.3% overflow nodes reduction and 42.2% inundation area reduction)