Ministry of Municipal Affairs and housing

Published purpose

In order to achieve the objective of mitigating the risk of natural flood disasters, the project has four elements (1) Rehabilitation of the east wall/dike (2) Rehabilitation of the west wall (3) Resilient redevelopment of the river (4) Shoreline stabilization. For the first element (1), since a portion of the wall gave way during the 2023 floods, it is imperative to repair this structure. The event also showed that the wall was not high enough for water levels like the one on May 1. The structure will also be raised. The final shape will be either a wall or a dike or a combination of these two shapes. It should be noted that this structure protects the Saint-Joseph/Ménard neighbourhood, which includes nearly 200 properties as well as a provincial road, Route 362. For the second element (2), since a portion of the wall collapsed during the 2023 floods, it is imperative to repair this structure. This structure protects the residences and businesses of Saint-Jean-Baptiste Street, which is the city's main street and heritage street. It should be noted that the subsidence of this structure could cause landslides and damage to properties that the structure protects less and less. For the third element (3), it is essentially a question of optimising the hydraulic section of the river, i.e. the space available for flow. This work is necessary because sedimentation over time has limited this space, increasing the water level and therefore the risk of flooding. Also, the wheelbase of the train bridge piers downstream of the section also creates a narrowing of the flow space that may have exacerbated the water level. Thus, work to redevelop the riverbed along the entire urban section will mitigate the risk by reducing the water level during flooding. This work, although oriented towards the reduction of natural risk, will also be relevant and interesting from an ecological point of view. Indeed, this part of the project will make it possible to give back space to the river and to rehabilitate river spaces. The work will be carried out according to a hydrodynamic design that respects the natural morphology of this type of watercourse. Other banks are at risk of erosion. Stabilization is necessary on these banks. All three elements of the project are intertwined and thought out in a global and coherent way. The hydraulic study will integrate this entire strategy into the evaluation of the project components.