Section 105

1

Objectives

• To ensure the free flow of water
• To ensure the lifespan of a road, bridge or culvert
• To avoid scouring of a watercourse
• To maintain a flow level and water level in the culvert that are sufficient to ensure the free flow of fish

Additional information

The decision tree below can be used to decide on the type of structure that must be installed to cross a watercourse.

Where the conditions specified in Schedule 9 cannot be met for a crossing site at which the free flow of fish must be ensured, section 106 provides that one or other of the following culverts may be installed:

1. A culvert including a conduit with outlets, designed and installed according to the conditions provided for in Schedule 10;
2. A culvert that meets other conditions, the installation of which was authorized by the Minister under section 41 of the Sustainable Forest Development Act  (chapter A-18.1), or the installation of which is authorized under a forestry permit or by a contract or an agreement entered into under the Act.

A person wishing to obtain authorization for this must apply to the regional office of the Ministère des Ressources naturelles et des Forêts  (in French only) by completing the form provided for that purpose. The application must describe the situation that justifies completion of the work in accordance with standards different from those enacted in the Regulation. It must also propose replacement measures that will be implemented to achieve the objectives of the regulatory standards from which a departure is requested. Where the proposed replacement standards fall within the approval framework, authorization may be granted along with conditions that must be met when carrying out the work.

In addition, regardless of the watercourse slope or the need to ensure the free flow of fish, section 107 provides that a bridge or culvert with an arch may be installed, provided it meets the conditions provided for in section 108.

When installing bridges and culverts on a stretch of water where the free flow of fish must be ensured, the structures must not become obstacles to the fish (e.g. insufficient depth of water, excessive water speed in the culvert or a vertical fall at the culvert outlet). Compliance with the standards set out in sections 103, 105, 106, 108 and 110 and with the conditions specified in Schedules 9 to 12 will help avoid situations such as these.

Why must the free flow of fish be ensured in a watercourse?1

Fish migrate throughout their lives, to access good quality habitats that will provide food, shelter and a place to reproduce. It is essential for fish to be able to circulate freely in order to meet their vital needs. If they cannot feed properly, they will be in poor condition, which may delay their growth, reduce their breeding success or make them easier prey for predators. During reproduction periods, obstacles may delay their arrival at spawning grounds or prevent them from reaching the best spawning grounds, thereby depriving them of suitable conditions for incubation of their eggs and compromising the survival of the young fish.

The presence of several structures limiting the upstream flow of fish in the same drainage basin will fragment the fish habitat and hinder the free flow of fish, and may also have a negative effect on fishing and harvesting, thereby creating significant social and economic impacts.

Fish flow may, in some circumstances, be limited in specific portions of a natural watercourse. It is therefore not necessary to ensure the free flow of fish everywhere, at all times. For example, the free flow of fish is not required if there is a permanent natural obstacle such as a waterfall or steep slope at the watercourse crossing site or nearby, or if the habitat upstream of the structure is marginal (i.e. small and of poor quality), or if the water conditions are unfavourable, because the fish will not swim upstream during these periods. On the other hand, the free flow of fish through the structure must be assured during periods in which water conditions are favourable to the migration for the species present in the watercourse.

Compliance with the standards set out in sections 103, 105, 106, 108 and 110 and with the conditions specified in Schedules 9 to 12 will ensure that the structures do not hinder the free flow of fish.

It is not necessary to ensure the free flow of fish everywhere, at all times. For example, the free flow of fish is not required if there is a permanent natural obstacle such as a waterfall or steep slope at the watercourse crossing site or nearby, or if the habitat upstream of the structure is marginal (i.e. of poor quality). On the other hand, the free flow of fish through the structure must be assured during periods in which water conditions are representative of favourable migration conditions for the species present in the watercourse. If these conditions are not favourable, the fish will not swim upstream, and it is therefore not necessary to ensure the free flow of fish through the structure during that period.

Structures that allow for the free flow of fish

Bridges

The most effective structures to ensure the free flow of fish are bridges in general and clear-span bridges in particular, where all the components span the watercourse without altering the bed or banks. Bridges allow natural flow conditions to be maintained by preserving the characteristics (substrate, slope and width) of the watercourse bed. A bridge also crosses a shorter stretch of water than a culvert, due to the absence of fill.

Culverts with an arch

Culverts with an arch, especially those for which all the work is performed outside the banks, are also effective in ensuring the free flow of fish, provided the characteristics of the natural watercourse are preserved or reproduced. In these situations, the fish encounter water conditions that are similar to natural water conditions in migration periods.

Culverts with a conduit

Culverts with a conduit can also ensure the free flow of fish if they are designed and installed properly.

• First, culverts can ensure the free flow of fish if the conduit is buried sufficiently deeply for the water to be pushed back upstream by means of a sill located downstream in the watercourse. This increases the level of the water and reduces water flow speed in the conduit. These conditions can only be created in watercourses with low-angle slopes.
• Culverts with a conduit equipped with outlets can also ensure the free flow of fish in watercourses with steeper slopes. Outlets are installed at regular intervals in the conduit to create a series of thresholds and basins that increases the level of water in the conduit and reduces flow speed. The water is pushed back towards the first outlet downstream of the culvert by a sill located downstream in the watercourse.

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¹ Authors: Collaboration, Ministère des Ressources naturelles et des Forêts and Fisheries and Oceans Canada

2

Objective

• To maintain a flow level and water level in the culvert that are sufficient to ensure the free flow of fish

Additional information

A culvert with a smooth wall conduit limits the free flow of fish because of its lack of roughness. The lower the Manning roughness coefficient of a conduit, the faster the water will flow through the culvert, and the shallower the water is likely to be. Conduits with a Manning coefficient of less than 0.022 are considered to be smooth wall conduits. Conduits made of concrete and high-density polyethylene normally fall into this category.

Some conduits with annular corrugated interiors, such as aluminized or galvanized metal pipe (ACSP, GCSP), create the conditions that are conducive to the free flow of fish despite having a Manning coefficient of under 0.022. Consequently, they are not considered to be smooth wall conduits.