1) A one-dimensional unsteady flow model was developed for the Surabaya River and its tributaries to simulate past flood events in Surabaya City, Indonesia. 2) The model was calibrated using hydrological data including rainfall, discharge hydrographs, and water level recordings. 3) Preliminary results show the model can simulate changes in water surface elevations over time within the river channels, but has limitations in representing actual inundated areas.