Chapter V – Roads, sandpits and forest infrastructures Division III – Bridge, culverts, removable structures and rudimentary structures §7. Stabilization of the bed, banks and riparian zone of a watercourse

Section 114

The bed, banks, riparian ecotone of a watercourse and the strip of woodland and land strip referred to in section 27 or 34 that have been disrupted during the construction, improvement, repair or removal of a bridge or a culvert or during the installation or removal of a removable structure must be stabilized immediately. The soil stabilization techniques used must allow the rapid reconstitution of the vegetal cover of the affected basal areas.

1

Objectives

To avoid carrying sediment into an aquatic, wetland or riparian environment
To promote natural regeneration

Additional information

A bed, bank or riparian ecotone of a watercourse or a strip of woodland or land strip referred to in section 27 or 34 must be stabilized immediately when disrupted. The risk of erosion may be reduced by carrying out the different phases of construction, improvement or repair work and stabilization as part of an ongoing sequence. The granular materials used and the soils exposed to erosion must therefore be stabilized as the work is being carried out. The strip of woodland referred to in section 27 is at least 20 m wide and is located alongside an open peat bog with a pond, a swamp, a riparian shrub marsh, a lake or a permanent watercourse. The strip of woodland is measured from the boundary separating the stand from the environment to be protected or, where there is a riparian ecotone, from the limit of the ecotone located furthest from the environment to be protected. The land strip referred to in section 34 is at least 6 m wide and is located alongside an open peat bog with a pond or an intermittent watercourse. The width of at least 6 m is measured from the boundary of the peat bog or the upper limit of the banks of the intermittent watercourse.

Materials with a sufficient gauge and stable enough to be flood resistant must be used when stabilizing the bed and banks of a watercourse.

2

Objectives

To avoid carrying sediment into an aquatic, wetland or riparian environment
To avoid scouring of a watercourse
To ensure the lifespan of a road, bridge or culvert

Additional information

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.