High efficiency integrated urban flood inundation simulation based on the urban hydrologic unit

As the impact of flooding intensifies globally in metropolitan areas, there is an urgent need for high-resolution flood forecasting models to facilitate preparedness and mitigate flood impacts. In response, we have proposed a high efficiency algorithm (HEA) designed to simulate urban flood inundation, leveraging the urban hydrologic unit (UHU) concept from an urban hydrological cycle perspective. The HEA significantly reduces the computational demands associated with high-resolution modeling by using a hydrologic unit derived from the digital elevation model (DEM). This approach effectively shifts the overwhelming burden of computational load to the hydrodynamic algorithm (HDA), which is grounded in the Shallow Water Equations (SWEs), thus enabling efficient flood inundation simulation crucial for time-critical decision making during extreme events. Our research also incorporated the HEA and HDA methods into a self-developed, distributed-framework basin modeling system, named the Taihu Basin Model (TBM). Both the HEA and HDA models were calibrated and validated with observed data on pipe level, flow rate, and inundation depth from our Shuangqiaobang experimental fields. Comparative analysis, focusing on simulated urban flood inundation distribution characteristics, simulation accuracy and timeliness, demonstrated the superior effieicney of the HEA method by three orders of magnitude. The consistency between observed data and the simulated results of both HEA and HDA models underscores the accuracy and reliablility of these models. The HEA model's simulated urban flood inundation distribution appears more patchy and localized compared to the HDA model, due to the generalization of urban UHUs in the TBM.