Urban flood modelling using computational fluid dynamics

The paper discusses the use of a code solving two-dimensional (2D) shallow-water equations in an urban area. Two application examples are described: a laboratory model representing low-density housing, and the city of Nimes (France), which suffered a catastrophic flood in October 1988. From these examples, the paper shows that such 2D models can provide general flow dynamics. Moreover, they can integrate description of some details (such as obstacles and storage areas), which can contribute to an understanding of some flow features and thus provide accurate results locally. For engineering use, the limits are computational time and number of cells: the two examples described show that a grid adapted to urban topography features is a way to reduce these disadvantages while providing reliable results with a convenient numerical stability, even if the size of the cells varies considerably.