[Objective] In urban flooding simulation，the loose coupling between surface flow and pipe networks fails to accurately describe bidirectional hydraulic exchange processes，and future urban underlying surface data cannot meet the fine-scale simulation requirements at the urban scale. To address these limitations，this study aims to simulate the pipe network overloading processes and surface inundation evolution under different rainfall scenarios and urbanization stages，providing a scientific basis for flood control planning and resilient city construction in riverside cities. [Methods] A tightly coupled 1D-2D hydrodynamic model was developed by integrating SWMM with LISFLOOD-FP，enabling real-time bidirectional data exchange between the surface and pipe network at a unified time step of 1 second. Three hydraulic exchange processes were considered： overflow from the pipe network to the surface，surface inflow into the pipe network via orifice flow，and weir flow. Design rainfall scenarios with return periods ranging from 1 to 100 years were generated using the Chicago rainfall pattern method with a duration of 120 minutes，and model parameters were calibrated using the comprehensive runoff coefficient as the calibration target. The Multi-engine Urban Expansion Simulator （MUSE） was introduced to simulate urban built-up area expansion from 2026 to 2040，adopting the Neighborhood-constrained Patch Growth Engine （Nei-PGE） and lognormal patch size distribution，with model accuracy evaluated using the Kappa coefficient，Figure of Merit （FoM），and Overall Accuracy （OA）. On this basis，the pipe network operating conditions and surface inundation response characteristics under different rainfall scenarios and future urbanization stages were systematically analyzed. [Results] （1） Model calibration results show that the coefficient of variation remains within ±10% across all return periods，confirming the model’s applicability. As the return period increases，the number of overflow nodes （NON） with overflow duration exceeding 2 hours rises continuously，reaching 79.17% of total nodes under the 100-year return period； the inundation area with water depth exceeding 1 m increases from 4.38 km² under the 1-year return period to 28.05 km² under the 100-year return period. （2） The urban expansion simulation achieves high accuracy，with a relative error of only 0.267% between the simulated and actual built-up area in 2024，a Kappa coefficient of 0.869，FoM of 0.573，and OA of 0.870； the urban built-up area is projected to increase from 95.485 km² to 131.453 km² during 2025-2040，with edge expansion as the dominant pattern alongside diversified internal infilling trends. （3） Under future urbanization scenarios，surface inundation risk intensifies progressively，with total inundation area under the 1-year return period increasing from 14.23 km² in 2026 to 22.98 km² in 2040，and inundation area with water depth exceeding 1 m under the 50-year return period increasing from 2.96 km² to 20.18 km². In contrast，the impact of urbanization on overflow node counts is relatively limited，with maximum NON variation not exceeding 4 nodes across urbanization stages under the same return period，indicating that the existing drainage network has approached saturation. [Conclusions] This study develops an integrated urban flood assessment framework coupling fine-scale hydrodynamic simulation with future urban expansion prediction for riverside cities. The tightly coupled hydrological-hydrodynamic model effectively captures the dynamic bidirectional hydraulic interaction between surface water and the drainage network，while the MUSE-based urban expansion simulation provides high-resolution future land use scenarios for flood modeling across multiple urbanization stages. The results demonstrate that as rainfall intensity increases，overflow nodes with shorter overflow duration progressively transition to longer-duration overflow. Urbanization significantly intensifies surface inundation risk，with shallow inundation areas gradually transitioning to deeper inundation zones as urbanization advances. In contrast，the impact of urbanization on overflow node counts is relatively limited，indicating that the existing drainage network has approached saturation，and that the effects of newly added impervious surfaces are primarily manifested as prolonged overflow duration and increased overflow volume rather than an expanded spatial distribution of overflow nodes.