Out of bounds: system structural uncertainty under extreme events

The study focuses on the Fossolo catchment in Bologna, which has been the subject of various modelling studies over the years. While previous research has focused on parameter optimization, limited attention has been devoted to model structure and boundary conditions. The study aims to investigate if the hypothesis of independence of subsystems is valid under extreme events. Two classes of models are developed in EPA-SWMM: one reflecting the original system structure and another based on a re-analysis of the system that incorporates downstream conditions. Sensitivity analysis reveals that downstream conditions impact parameter sets during extreme events, with pipe and impervious surface roughness being the most sensitive parameters.