Flooding is identified as one of the main causes of NaTech events (“Natural hazard triggering Technological disasters”) targeting the electrical grid, with material damage to electrical substations, whose flooding can cause outages and blackouts.

SPHERA (RSE SpA) is a 3D code based on the SPH numerical method of computational fluid dynamics (CFD), focused on simulating floods and landslides for the safety of hydroelectric plants, electrical substations, and power line supports. Among the few 3D CFD codes for hydrogeological risk on complex topography, SPHERA has been improved and used for the 3D CFD analysis of an urban river flooding scenario, aimed at quantifying the flood damage to the Calenzano (Florence) electrical substation. A numerical scheme was developed for the slip coefficient as a function of roughness and a scheme for handling Dirichlet boundary conditions for water depth. Regarding estimates of this 2D magnitude, an inter-comparison between SPHERA and the FLORA2D code (University of Basilicata, RSE SpA) was performed, highlighting the performance characteristics of each software regarding computational speed, accuracy, functionality, and application fields. Due to the lack of available measurements in any flow regime along the analyzed watercourse, the damage analysis can only be demonstrative.

Additionally, due to the lack of flooding of the electrical substation in the SPHERA simulation, the damage analysis only indicates minimum distances from the liquid front and some conditions of particular criticality. The SPHERA damage model for electrical substations was effectively productive in a refined application for the dam-break flood of Alpe Gera, impacting residential areas and the Lanzada (Sondrio) electrical substations. This application quantified the benefits of the new slip coefficient scheme. For both case studies, among the 2D output variables of SPHERA, the estimates of maximum water depth were prepared for input to the FloodRisk2 damage code (University of Basilicata, RSE SpA). The RSE software tools in the SPHERA modeling chain are available as FOSS (Free/Libre Open-Source Software) on github.com.