**2. Materials and Methods**

This study incorporates Barcelona Metro Line 3 real data into the hydrodynamic 1D/2D model of Barcelona considering the connections among possible water inflows and Metro tunnels and stations and considering them as pipelines. To summarize the overall structure of the model, Figure 3 lists the necessary steps performed for the proposed flood risk assessment.

**Figure 3.** The overall model structure for flood risk assessment in Metro systems.

This chapter presents a list of the precipitation events in Barcelona that have caused disruptions in the Metro service due to the entry of water into the system, considering both the sources and methods of study, with the hydrodynamic model implementation, the Metro Line 3 data acquisition, and components' introduction processes to the model. Furthermore, this chapter describes the model calibration and validation process, along with the flood risk assessment under the impact of climate change.
