Author(s): Gabriella Petaccia; Elisabetta Persi
Keywords: Bridge; 1D unsteady flow model; Internal boundary conditions; Hydraulic structures
Abstract: Bridges or hydraulic structures can increase flood risk in closer areas due to their obstruction to the flow. The presence of bridges can also increase large wood or debris deposition at the bridge cross-section, reducing the wetted area and bringing an additional water rise upstream of the structure. Even if the use of 2D fully dynamic models represents the most reliable approach for flood inundation studies, 1D models are still widely used in practical applications due to the reduced computational costs. This paper focuses on one-dimensional flood wave propagation through hydraulic structures. Different flow regimes can occur at bridges, like transition through the critical state, pressure flow, and overflow. The commonly adopted De Saint Venant Equations (DSVE) model cannot represent all these phenomena. The authors propose to couple internal boundary conditions with the mass or the momentum equation of DSVE. The original model is verified first on an exhaustive experimental campaign performed at the LIFTEC-CSIC Laboratory of Zaragoza University. The efficiency of the method is finally assessed by its application on a real-world case study: a 16 km reach of the Lambro River, a case study selected for the FLORIMAP project, Smart Flood Risk Management Policies, funded by the Cariplo Foundation in 2017. The proposed model reproduces every transition occurring in the flow regime, without the need for any calibration.