Chapter V – Roads, sandpits and forest infrastructures
Division III – Bridge, culverts, removable structures and rudimentary structures
§4. General provisions applicable to bridges or culverts
During the construction, improvement or repair of a road, the bed of the watercourse upstream and downstream of a bridge or a culvert must be stabilized at the time of the work with adequate materials to prevent the scouring of the bed and ensure the free circulation of water and fish if the free flow of fish must be ensured by reason of the absence of any of the situations described in section 103.
- To avoid scouring of a watercourse
- To ensure the lifespan of a road, bridge or culvert
During construction, improvement or repair of a stretch of road that includes a bridge or culvert, the bed of the watercourse upstream and downstream of the structure must be stabilized using adequate materials to prevent scouring.
The materials used to stabilize the watercourse bed must be able to support the water flow speed so that they are not eroded and carried away by the current. A variety of materials similar to those that make up the natural bed of the watercourse should be used (rounded materials with a variety of particle sizes), and they should be arranged so as to overlap one another. This ensures that the reconstituted bed is watertight, and that water cannot filter through the materials. The addition of large stones (roughly 1.5 times the size of the largest stones in the natural watercourse), scattered across the bed, will improve stability and prevent scouring. The presence of large stones also helps to create a variety of flow conditions and also to create shelter for fish. When the stones are installed, it is important to ensure that they are nested and anchored in the underlying substrate, by partially burying them.
- To ensure the free flow of water
- To ensure the free flow of fish
The materials used to stabilize the bed of the watercourse must not hinder the flow of water or the flow of fish, in a watercourse where the free flow of fish must be maintained. Section 103 provides information on the watercourses in which the free flow of fish must be maintained.
When installing a bridge or culvert, as little work as possible must be carried out in the bed of the watercourse upstream and downstream of the structure. This promotes stability of the bed and minimizes the need for stabilization work..
To avoid hindering the free flow of fish, the stabilized bed:
- must be composed of materials that are embedded and anchored in the underlying substrate;
- must be watertight to prevent water from filtering through the materials making up the bed, which would render the depth of the water insufficient;
- must not include a waterfall or vertical drop that is too large, which would create a barrier or excessive flow speed;
- has a channel that provides a sufficient depth of water at low flow.