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 that crosses a watercourse, a culvert must be installed so as to ensure the free flow of fish, except if, less than 250 m upstream or 500 m downstream of the crossing site, any of the following situations is present:
- there is the presence of a vertical fall more than 1 m high, measured from the surface of the water, and no spawning ground identified on the land or indicated in the numeric information layers used for forest planning is present between the fall and the crossing site;
- the bed of the watercourse has a section of smooth bedrock with an average slope of 5% or more over a minimum distance of 3 m and the depth of the water flowing over the entire section is less than 100 mm;
- a section of the watercourse has a slope equal to or greater than 20%, evaluated using the department’s topographical maps or observed on the site over a distance of more than 20 m.
A culvert need not be installed to ensure the free flow of fish where, less than 250 m upstream from the crossing site, the bed of the watercourse disappears over a distance of more than 5 m.
It is also acceptable not to secure the free passage of fish if, least than 500 m downstream from the crossing site, the watercourse bed (mapped or not) disappears on a distance of more than 5 m, since this is an obstacle to the free passage of fish.
Subparagraphs 1 and 2 of the first paragraph do not apply to a watercourse frequented by Atlantic salmon, ouananiche, Arctic char of the oquassa subspecies and anadromous brook trout.
For the purposes of this section, beaver dams, wood debris and anthropogenic obstacles are deemed not to be obstacles to the free flow of fish.
- To ensure the free flow of fish
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 presented in Schedules 9 to 12 will ensure that the structures do not hinder the free flow of fish.
Structures that allow for the free flow of fish
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.
¹ Authors: Collaboration, Ministère des Forêts, de la Faune et des Parcs and Fisheries and Oceans Canada
Specific conditions for certain types of work
Improvement or repair of a stretch of road that crosses a watercourse
When improving or repairing a stretch of road that crosses a watercourse, it is not necessary to install a new structure if the conduit or culvert is in good condition (i.e. if the structure is stable and allows the water to flow freely). However, if the work affects the conduit itself (e.g. extending its length or replacing it when the road is widened), the structure must allow for the free flow of fish after the work, except if one of the situations described in section 103 is present.
Construction of a culvert to cross an effluent or tributary of a lake in which Arctic char of the oquassa sub-species are present
Arctic char of the oquassa sub-species is a freshwater fish found in Québec south of the 52nd parallel. It is on the list of wildlife species likely to be designated as threatened or vulnerable. The Centre de données sur le patrimoine naturel du Québec (CDPNQ) defines the boundaries of an occurrence of oquassa Arctic char as being the area of a lake in which such a fish has been observed or caught, or of a lake in which a spawning ground has been observed. The species is generally found in deep, coldwater, transparent, well-oxygenated oligotrophic lakes (i.e. lakes poor in nutrition). It usually spends its entire life cycle in the lake, and is therefore not often found in watercourses.
It is therefore not necessary for a culvert crossing an effluent or tributary of a lake in which Arctic char of the oquassa sub-species are present to be built in such a way as to ensure the free circulation of the species if one of the situations described in section 103 is present less than 250 metres upstream or 500 metres downstream of the crossing site. This includes the following situations:
(1) there is the presence of a vertical fall more than one metre high, measured from the surface of the water, and no spawning ground identified on the land or indicated in the numeric information layers used for forest planning is present between the fall and the crossing site;
(2) the bed of the watercourse has a section of smooth bedrock with an average slope of 5% or more over a minimum distance of three metres and the depth of the water flowing over the entire section is less than 100 mm.
It goes without saying that section 103 applies in its entirety to other species of fish. Consequently, the requirement of ensuring the free flow of fish when constructing a culvert must be determined on the basis of the situations described in that section.
Installation of a culvert to cross a watercourse with a width of 600 mm or less
The rational method prescribed in Schedule 6 is used to establish the 10-year interval peak flow (Q10) at the crossing point of the watercourse for drainage basins having an area equal to or less than 60 km². This method is based on several hypotheses, and as a result may not be well adapted to certain drainage basins. Indeed, sometimes significant differences can be observed between the calculated peak flows and the flows recorded in small rivers associated with small watersheds.
In this context, the following conditions must be applied for watercourses with a width of 600 mm or less, mapped or not:
- The culvert does not need to be laid out in a way that ensures free flow of fish. As a result, there is no need to verify if any of the situations described in the first and second paragraphs of section 103 are present.
- The culvert must be laid out in accordance with the following conditions:
- the diameter of the conduit must be at least 450 mm;
- the conduit must be installed following the natural slope of the watercourse and be buried under the watercourse bed to a depth equivalent to 10% of its diameter, without however exceeding 500 mm, regardless of its size;
- the culvert may include one smooth wall conduit or two in the case of parallel conduits.
- When the diameter of the conduit determined according to the calculated peak flow is greater than the width of the watercourse, the conduit installed must belong to the diameter class closest to the average width of the watercourse. The conduit must in no case reduce the width by more than 20%, measured at the upper limit of the banks.
- When the diameter of the conduit determined according to the calculated peak flow is less than the width of the watercourse, the conduit installed cannot reduce the width of the watercourse by more than 50%, measured at the upper edge of the banks. It is acceptable not to calculate the peak flow rate of the watercourse before installing the culvert provided that the conduit installed is in the diameter class closest to the average width of the watercourse.
- If, under Section 101, the Minister requests the calculation of the peak flow of the watercourse, the reason that guided the choice not to make this calculation before the work must be provided within 48 hours.
How is the width of a watercourse measured?
The width of a watercourse is determined using the average of at least four representative measurements of the natural watercourse taken upstream and downstream from the crossing point. If signs of narrowing or broadening are present, the section concerned must be excluded (for example, a zone disturbed by a beaver dam). The width is measured at the upper limit of the banks, determined as indicated in the definition of “bank” or “shore”.