Résumé
The Brague River (south-east France) has historically been subjected to significant flooding events, notably recently in 2011, 2015 and 2019. This research primarily focuses on the 2015 flood event, which resulted in human loss and significant damage. In the study domain, several hydraulic structures across the river (e.g., under the A8 highway), which can hinder the river flow during extreme flood events. Our objective in this work is to assess the influence of culvert representation within the domain on hydraulic discharge, particularly beneath roadways, and to examine the resultant variations in flood extents and water depth. To this goal, the TELEMAC-2D hydraulic modelling software is used to simulate a range of modelling approaches that account differently for the flow in the culvert areas, such as opened or closed topography or using culvert discharge equations. Five scenarios concerning the highway culverts are proposed. The numerical results are analysed and intercompared with field observations. The results reveal a significant reduction in culverts flow rate upon the formation of logjams, while the highway overflow increases. These studies' findings could help in guiding management policies and practices, offering a scientific foundation for decision-making in the context of flood events involving hydraulic structures.