Internal Boundary Conditions for Flood Simulation with 2D Shallow Water Equations Using Finite Volume Models: Bridge Piers

River flood events are usually simulated with the two-dimensional (2D) Shallow Water Equation (SWE) model using Finite Volume methods. In this kind of model, the presence of hydraulic structures such as bridge can be accounted for in different ways. Here, two alternative bridge representations to be used in 2D mesh, with reflective solid wall conditons applied along the hole boundary. The second approach consists in modelling the bridge axis as an internal boundary conditon, exploiting the Riemann problem concept. The performance of the two different bridge representations is assessed via a simple dam-break test case in a rectangular channel with a singl bridge pier.