An enhanced inundation method for urban flood hazard mapping at the large catchment scale

•EIM was proposed for urban flood hazard mapping at the large catchment scale.•SWMM model was introduced in floodwater generation process.•Floodwater spreading was based on topological relation of depression outlets.•Floodwater from lower depression elements was considered in EIM.•The performance of EIM was validated in terms of inundation locations and depths.