*2.4. Integration of the Metro Infrastructure in the Hydrodynamic Model*

Water presence in the tunnel and the stations of a Metro system affects the continuity of the service. Thus, this study represents Metro network components into the hydrodynamic model through the creation of hydraulic geometry elements, comparable to real infrastructure components, evaluating a conceivable water entry event into the system, through hydrodynamic modelling. Principal floodwater access to the Metro system during extreme precipitation events are the ventilation grates and stations' entrances, according to TMB and visual inspections carried out by TMB personnel during extreme rainfall events.

The data required to calculate the flow intercepted at the ventilation grates depends on the modelled inlet type. InfoWorks ICM®offers various methods to estimate captured flow by inlets, two of them based on the Federal Highway Administration (FHWA) Urban Drainage Design Manual, Hydraulic Engineering Circular No. 22 (HEC-22) [44]. This study applies another method, an alternative to the HEC-22 continuous grate inlet based on the equations from work carried out by Gomez et al. [45] at the Technical University of Catalonia (UPC), implemented in the InfoWorks®ICM software package.

Three-dimensional numerical modelling experimental campaigns [46,47] executed at UPC characterizes Barcelona drainage grates' hydrodynamic behavior [45,48,49], including physical obstruction conditions determining hydrodynamic efficiency decrease on partially clogged grated inlets [50]. The ventilation grates as a water inlet use this previous research outcome since the model integrates hydrodynamic equations representing urban drainage grates, comparable to ventilation grates.

Metro tunnels' representation in the hydrodynamic model introduces pipes with identical dimensions and geometry to the real infrastructure, considering tunnels' cross-section and elevation data as Figure 6 shows. Metro network elements' depiction in the hydrodynamic model process disregards entrance to service tunnel variability, which simplifies the flood impact analysis on the stations' platform and tunnels.

**Figure 6.** (**a**) Image (up) and essential features (down) of a typical surface grate for ventilation purposes in the Barcelona Metro system; (**b**) Catalunya Metro station cross-section drawing (up); tunnel depiction shape in ICM®software (down).

Reaching a proper representation of Metro entrances requires gathering information such as longitude, altitude, stairs slope, and the elevation difference with the tunnel service, to set the pipe connecting them. An evaluation and calibration process for different inlet types concludes, in this case, that the continuous curb-opening inlet typology provides a better representation of Metro station entrances' hydrodynamic behavior.
