Large-scale high-resolution hydrodynamic modelling of urban floods: Some practical considerations

The last few years have witnessed a series of catastrophic urban flood events across the world. This type of extreme events has become more frequent due to climate change. Numerical modelling provides an indispensable means to support flood risk assessment and management. Simulation of the highly transient flood dynamics induced by intense rainfall requires the use of high-resolution hydrodynamic models. Accurate flood prediction needs proper representation of infiltration and drainage processes in complex urban environments, which requires high-quality soil and drainage data that are not widely available. This paper considers these challenges and explores practical approaches to integrate a high-performance hydrodynamic model with high-resolution topography data and crowd-sourced flood observations to address data gaps and support real-time simulation of urban flooding. The model is applied to reproduce a real-world flood event in the 400 km² Tyneside metropolitan region in the UK at a 2 m resolution, with solution accuracy confirmed by crowd-sourced data. Different simulation strategies are implemented to reflect the impact of infiltration and drainage on surface flooding. It is demonstrated that infiltration and drainage capacity may be considered using conceptualised mass loss parameters, which produces better results than direct reduction to the rainfall rate. Such an approach offers a practical solution to support high-resolution urban flood modelling in large cities, particularly when essential drainage and soil data are not available.