Urban flood analysis in plain river network regions is complex. A new model was created to simplify flood simulation for small tributaries and their flood control projects. The model defines river network drainage units and calculates municipal drainage system capacity. By combining different models and considering tides, the researchers built an urban flood analysis model for plain tidal river network regions. Using Shanghai as an example, they found that simulated tide levels matched observed data. Overflow occurred at specific rivers, in line with actual events.