Citywide multi-grid urban flood modelling: the July 2012 flood in Beijing

Global flood management is a major issue for most cities which have to deal with worsening factors such as climate change and fast urban growth. Computer models have been used to model and understand urban flooding on a local scale in cities (25-50km(2)). It has been practically impossible to model bigger cities in one go in sufficiently high resolution due to the heavy computations involved. The present paper describes a new modelling approach for urban flooding which allows modelling on large city scale (1000km(2)) while keeping sufficient resolution, e.g. 5m or 10m grid. The multicell approach is applied for the city of Beijing for July 21st, 2012 flood event. Model results are compared to testimonials from the 2012 event. Comparison to traditional 2D urban flood computations shows that the multicell approach is much faster than standard detailed models while keeping a suitable level of precision.