Upscaled shallow water modeling with SW2D-Lemon for urban flood simulation

We present a new multi-OS platform named SW2D-LEMON (SW2D for Shallow Water 2D) developed by the LEMON research team in Montpellier.

SW2D-LEMON is a multi-model software focusing on shallow water-based models. It includes an unprecedented collection of upscaled (porosity) models used for shallow water equations and transport-reaction processes. Porosity models are obtained by averaging the two-dimensional shallow water equations over large areas containing both a water and a solid phase. The size of a computational cell can be increased by a factor 10 to 50 compared to a 2D shallow water model, with CPU times reduced by 2 to 3 orders of magnitude. Applications include urban flood simulations as well as flows over complex topography. Besides the standard shallow water equations (the default model), several porosity models are included in the platform: (i) Single Porosity, (ii) Dual Integral Porosity, (iii) Depth-dependent Porosity. Various flow processes (friction, head losses, wind, momentum diffusion, precipitation/infiltration) can be included in a modular way by activating specific execution flags.

Classical input data are required by SW2D-Lemon software: mesh file (several formats available) with elements having an arbitrary number of edges; geometric and hydraulic parameter fields: bathymetry, porosity, Boussinesq/Coriolis momentum distribution coefficient, friction coefficient fields, etc.; initial and boundary conditions (several types available) and forcings (wind, rainfall).

SW2D can be used in two ways: in command-line mode or via a dedicated graphic user interface (GUI). Both features are available on all Windows, MacOS and Linux operating systems. SW2D is available under three license modes: Academic Research (source code, developer manual and basic configurations are freely available in the framework of a scientific partnership with the LEMON team), Industry and education.

Various real-world test cases will be presented to illustrate the potential of SW2D and the contribution of porosity based models to urban flood modelling:

- Flood simulation on Sacramento city induced by the breach of a dike;

- Marine submersion on Valras Plage;

- Fast rain flood on the Abidjan Riviera district.