Flood simulation in urban areas obtained by GPU-accelerated 2D shallow water model with internal boundary conditions

In this paper, the integration of Internal Boundary Conditions (IBC) in the two-dimensional shallow water model “PARFLOOD” is described. The proposed formulation, designed to minimize code branching, requires slight modifications to the numerical scheme only at selected cells and edges in the domain, and is compatible with the GPU implementation of the code. The model is applied to the simulation of a real flood event, occurred in October 2014, where the presence of bridges contributed to the partial inundation of the city of Parma (Italy). Results show that the IBC model satisfactorily predicts backwater upstream of bridges and the subsequent lateral overflows. Moreover, despite the high-resolution mesh used to discretize the urban area, a physical/computational time ratio around 20 is obtained, confirming the computational efficiency of the code.