Cartino2D: Scalable and Automated 2D Shallow Water Rainfall-Flood Inundation Modeling up to Very High Resolution for Large Domains

Abstract. While 2D shallow water models with rainfall and infiltration provide a physically consistent framework for flood inundation modeling, their automated application at large scales remains constrained by challenges related to unstructured mesh generation, parameter specifications, and the integration of heterogeneous geospatial and hydrological datasets. This study presents Cartino 2D (C2D), a novel automated framework that enables the large-scale deployment of the well-established Telemac2D model, for solving the complete 2D shallow water equations, with flexible, spatially distributed hydrological forcing—either from rainfall fields or discharge hydrographs. C2D features topography-aware unstructured mesh generation, optional automated handling of hydraulic structures, and spatial parameter estimation from diverse datasets, including land use. It supports multi-resolution simulations up to very high (metric) resolutions and includes optional automated flow analysis at user-defined transects. The framework also features an automatic subdomain sectorization step, based on preliminary simulations on a regular grid, to delineate hydrologically-hydraulically consistent regions and inform targeted unstructured meshing procedures. The framework is successfully applied at the national scale across France, using 100-year return rainfall and discharge values from the SHYREG database, as well as at very high resolution in the complex metropolitan area such as the Aix-Marseille Provence or Grabels City, demonstrating both scalability and robustness. Model outputs are evaluated using flood marks and firefighter intervention records, showing encouraging hydrological and hydraulic consistency. This advancement opens new opportunities for large-scale flood hazard pre-assessment in France and can be transposed to other countries using global and/or national data. Future work will focus on improving culvert representation, testing alternative infiltration models, and extending the framework for model parameter optimization, coastal flooding and real-time applications.