Beavers are regarded as ecological engineering wonders – and now Banff National Park is relying on some manmade engineering solutions to retain vital beaver habitat in the Bow Valley.
Parks Canada is embarking on a $26 million project to replace an aging wildlife exclusion fence along the busy Trans-Canada Highway, but the fence runs through several areas that beavers have turned into impressive wetlands.
Officials say there are two beaver dam areas that are causing particular concern – one along the Legacy Trail and the other by the Norquay interchange where culverts beneath the highway are being affected.
“Where we’re able to, we’re going to re-route the fence design to keep out of the wetlands beavers have created,” said Bill Hunt, resource conservation manager for Banff National Park
“But there’s a few spots, one at Norquay interchange and the other along the Legacy Trail, where they’ve basically backed up enough water that it’s impacting the effectiveness of the culverts under the highway.”
Beavers are known for unprecedented feats of ecological engineering – building dams, ponds and wetlands that can flood and damage human infrastructure – and are persecuted by humans as a result.
But they are also considered a keystone species, creating ponds that consistently have higher waterfowl diversity, more complex invertebrate communities, and provide critical habitats for amphibians.
The buck-toothed creatures also create habitats that provide flood mitigation and resilience to extreme drought.
Hunt said when beavers cause problems for human infrastructure, the traditional go-to solution has long been to live trap or kill beavers, or go in with heavy equipment to destroy their dams.
“None of those historic remedies are very appropriate these days,” said Hunt. “We’d like to come up with solutions that work to ensure water flows through the culverts, but also preserves the habitat for the beavers.”
Beavers probably see a culvert beneath a road as a hole in an otherwise good dam, so they try to plug the hole. Parks is using flow devices, which are relatively cost-effective, low-maintenance solutions that regulate the water level of beaver dams and keep culverts open.
At the dam near the Norquay turnoff, Parks Canada has used a so-called Beaver Deceiver, a trapezoidal shaped culvert fence and some associated pipes, which are known to be effective at eliminating beaver damming of a culvert.
First, the perimeter of the trapezoidal fence is typically long, making it difficult for a beaver to dam the entire fence. Second, as beavers try to dam the culvert, the fence forces them to dam in a direction away from the culvert, which is not in their nature. Third, as they dam farther out on the fence, the opening of the stream into which it flows gets wider.
Therefore, the damming stimuli of the sound and feel of moving water decreases the farther beavers dam on the fence.
For dams that are below a culvert, and backing water up into culverts, Parks is using what’s known as a Clemson Leveller – a length of plumbing pipe that allows water to pass through the dam, but does it quietly so beavers are less inclined to notice.
“What stimulates beavers building is the sound of rushing water. It drives them crazy and the leveller device moves this noise downstream,” said Hunt.
Hunt said the work at the Norquay site was completed about two weeks ago.
“We’ve been able to top the level of ponding area by about a foot, which is allowing the culvert to continue functioning,” he said. “We’ll continue to see how it functions and look at what maintenance efforts are needed.”
Hunt said Parks Canada is looking at applying a similar approach to the beaver dam by the Legacy Trail.
But, he said, this work has to be done around a window of opportunity important to fisheries as it’s believed there are brown trout and brook trout in the waterway.
“The Legacy trail one is a little bit trickier,” he said. “There are several dams and the gradient is much steeper.”
Beavers are North America’s largest rodent and they are built for life in the water.
The most remarkable characteristic is the beaver’s tail, which is flat and has scales.
They use it as a prop while cutting down trees, a rudder while swimming, a fat reserve in winter, a cooling device, and even an alarm when warning others in the colony of imminent danger.
Glynnis Hood, author of the Beaver Manifesto and an associate professor of environmental science at the University of Alberta’s Augustana Campus in Camrose, said she was pleased to hear about the work that Parks Canada is doing.
She said she has installed 29 flow devices since 2011 in various places, including at Cooking Lake-Blackfoot Provincial Recreation Area, as well as in the rural municipality of Beaver County.
“I think what Parks Canada is doing is great, especially in a national park,” she said. “I’ve installed many of these devices in various places and the success rate has been very high. There’s been minimal to no maintenance on most.”
Hood, who studies wetland ecology as it relates to wildlife habitat and management, said she started to look into some of these flow devices because she was tired of seeing beaver habitat destroyed.
“I’m an ecologist, but over time I’ve turned into a wetland plumber because I was tired of seeing these wetlands, and specifically ones that are occupied and modified and transformed by beavers, with the highest biodiversity, disappear,” she said.
“I would be at a beautiful pond, with nesting songbirds, tadpole, frogs and waterfowl and then the next day I would go back and it would be drained because of management concerns. I thought ‘there’s got to be a better way.’ ”
Beavers play a vital role in the environment and are referred to as a keystone species.
“When beavers are in areas, it ends up supporting many other species that otherwise wouldn’t have habitat,” said Hood. “They do remarkable things.”
Parks Canada is hoping to showcase the work to be done at the beaver dam by the Legacy Trail to educate how important beaver habitat can be saved instead of destroyed.
“It’s one of the best beaver dam viewing opportunities in Banff National Park, and it’s completely and totally accessible,” said Hunt.
“It’s like a demonstration project. We really want to show there are ways to allow beavers on the landscape without having the detrimental effects people often associate with them.”
