Wood Debris Risk Analysis and Protection Scenarios of Lourdes City Using Iberwood Model

International audienceLarge wood (LW) accumulations can cause several damages, especially if the recruited wood is transported during floods down to urban areas, like Lourdes (France). One of the most serious problems concerning bridges and weirs all around the world, is the formation of LW accumulations, that might be responsible for the structure’s failure. However, the transport and deposition of LW during floods are very complex processes, which make predictions of these accumulations’ locations and potential impacts very challenging. Thus, reducing the LW-related risks is difficult. Thereby, we are conducting a study to assess the LW-related hazards by applying a numerical model of the Gave-de-Pau River. The software called Iber-Wood is a hydrodynamic model based on the 2D Saint Venant equations coupled to a wood dynamics module that simulates wood transport explicitly. It allows analyzing LW accumulations’ formation, depending on several input parameters. The aim of this study was to simulate wood transport during floods, in order to identify the potential risks created by the formation of LW accumulations in Lourdes’ city center. The paper first proposes a framework to calibrate the parameters of LW-supply (flux and size of logs) based on the typical dataset available in France. It then presents a preliminary study of the 2D hydrodynamic model showing its potential to identify preferential storage areas and bridges prone to the formation of LW accumulations. The calibration phase of the model is not finished but we can yet highlight some recommendations on LW-transport modelling from this early stage results