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Writer's pictureFreshwater Conservation Canada

Cold, Clean, Complex, Culverted?

Cold, Clean, Complex, Culverted? By Lili-Maude Craig, Fisheries Technician

Culverts can effectively convey water below a roadway; however, they are not always suitable passageways for stream inhabitants, especially when inadequately sized. Undersized culverts funnel all of a stream’s water into a narrow corridor. When the flow becomes constricted, it increases in speed. The fast-moving water from the culvert can scour out the streambed, causing the culvert to become higher than the stream below; this creates a complete barrier to fish passage. Unfortunately, Canada has many undersized, hanging culverts that are preventing the upstream and downstream movement of fish. For this reason, Trout Unlimited Canada (TUC) launched the Reconnecting Canada Campaign, which aims to restore access to habitat for native fishes.

An unnamed tributary to Waiparous Creek, referred to as Whispering Pines West, was slated to be reconnected as part of this campaign. The entire Waiparous Creek watershed is within a priority area for native trout recovery. Provincially and federally threatened populations of Westslope Cutthroat Trout and Bull Trout are found within this system. Both species require “cold”, “clean”, “complex”, and “connected” habitats to thrive. However, a set of perched culverts in Whispering Pines West acted as a source of chronic sedimentation and starved downstream reaches of structure. Debris, such as branches and leaf litter, would get stuck at the culvert inlet, preventing what could be useful cover for fish from accumulating downstream.

Whispering Pines West culvert

Sediment-laden water spilling out of the Whispering Pines West culvert during heavy rain


The crossing contained not one, not two, but five stacked, undersized culverts that likely fragmented critical habitat decades ago. The overhang of the culverts prevented Bull Trout from accessing upstream habitat for feeding, spawning, and rearing. A population of Westslope Cutthroat Trout was also isolated above the culverts, which put them at greater risk of local extinction from stochastic events. This population had limited options for refugia during harsh environmental conditions and lacked gene flow. Therefore, these fish were more likely to suffer declines from droughts, floods, inbreeding or genetic drifts, in addition to the list of threats this species already faces.

The site was identified in 2018, and after many years of planning and fundraising, work to replace this barrier with an open-bottom arch finally began in September 2022. Prior to construction, the work site was isolated, and a fish salvage was completed. Backpack electrofishing was conducted upstream and downstream of the crossing until there were two passes without any fish. In this small, seemingly fishless tributary, a total of 39 fish were captured within a 30-meter section: 9 of those were Westslope Cutthroat Trout, and 30 were non-native Brook Trout. All fish caught were relocated upstream of the project area, and the site was dewatered for construction.

Westslope Cutthroat Trout

Westslope Cutthroat Trout (left) and Brook Trout (right) captured during the fish salvage before construction.


Construction took place over seven long days, with the help of many individuals. The old culverts were removed, and a geotextile reinforced soil (GRS) arch manufactured by Atlantic Industries Limited was installed. After construction, bioengineering was completed along the crossing and on the banks. Staff from Big Rock Brewery assisted with live willow staking, distributing woody debris, moss and leaf litter, and installing erosion and sediment control measures.

the footings for the culvert

Preparing the footings for the arched crossing


culvert

Assembling the arch


The new GRS arch is self-sustaining, requiring less maintenance than regular culverts while allowing natural stream processes to continue. Fish will have unimpeded, year-round access to habitat to carry out their life cycle. A set of inadequately sized culverts in another tributary to Waiparous Creek (Whispering Pines East) is planned to be replaced in 2023, pending funding. The removal of both problematic crossings will help fulfill the four “C’s” required by at-risk Westslope Cutthroat Trout and Bull Trout, ensuring the long-term persistence and growth of these populations in the Waiparous Creek watershed.

Culvert

Unfit crossing in Whispering Pines West before its replacement.


Culvert

Completed geotextile reinforced soil arch.


This project was financially supported by the Alberta Fish and Game Association, Environment and Climate Change Canada, Forest Resource Improvement Association of Alberta, Samuel Hanen Society for Resource Conservation, Land Stewardship Centre, Bass Pro Shops and Cabela’s Outdoor Fund, Alberta Conservation Association, and Alberta Environment and Protected Areas through the Native Trout Collaborative. In-kind support has been gratefully received from the Blackfoot Confederacy, Ghost Watershed Alliance Society, Cows and Fish, Alberta Environment and Protected Areas, Alberta Transportation, Downer Contracting, and Big Rock Brewery. In addition, TUC would like to thank Whispering Pines Bible Camp for their willingness to partner with us on this project and all the volunteers who contributed their time and efforts.

For more on this project, check out “What a difference; stream work helps restore fish habitat.” by Michael Short of “Let’s Go Outdoors”


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