Insight into the digital twin of Hanover: real-time modelling of flooded areas

Abstract

The Digital Twin platform developed for the “ZwillE” research project in Germany serves different purposes, covering a wide range of urban water management tasks of the wastewater utility of Hanover in Germany. Fundamental concepts, such as model integration issues and different use cases with different levels of complexity are tackled within the project. This contribution focuses on a new approach for the fast estimation of maximum water levels for use in relatively flat urban environments. The approach combines pre-calculated flood maps based on design rainfall for fixed return periods with real-time radar measurements and radar nowcasts, including uncertainty information. An evaluation with 10 extreme precipitation events in Hanover, between 2002 and 2023, was performed, where an observed flooding, and a high number of fire brigade calls were registered throughout the city. Forecast and Maximum forecast precipitation conditions are also included and validated. Results of the new approach for fast flooding estimation are assessed in comparison to fire brigade calls and to a coupled 1D sewer and 2D surface runoff simulation using the model Hystem-Extran/Hystem- Extran2D. The fast estimation shows good results of the maximum water level in comparison to the reference simulation, with absolute differences mostly below 0.1 m or 0.2 m respectively. The approach is suitable for real-time application in the newly developed digital Twin for the city Hanover.