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'Catastrophic draining' damages beaver dam

“The concerns have mainly centred around the timing of the beaver dam removal and the amount of water drained, leaving early wetland nesters high and dry.”
A beaver swims through open water in a melting pond.
A beaver swims through open water in a melting pond. RMO file photo

BANFF – Beavers are nature’s ecological engineers but have long been persecuted for the damage they do to human infrastructure.

So when Parks Canada diverted water from a beaver dam in the Cave and Basin marsh loop in early May to prevent flooding, conservationists were quick to flag concerns, including for birds during the sensitive spring nesting period.

The Bow Valley Naturalists say the “catastrophic draining” caused water levels to significantly drop in an area of Banff National Park designated for special protection, damaging the beaver dam and exposing the entrance to the lodge.

The beavers were seen busily piling mud on top of their dam as a result.

“It’s reported that the water levels have dropped two to three feet in the marsh area,” said Reg Bunyan, past president of Bow Valley Naturalists.

“The concerns have mainly centred around the timing of the beaver dam removal and the amount of water drained, leaving early wetland nesters high and dry.”

This is in about the same location the marsh was drained with disastrous results due to beaver activity in the 1980s.

Beavers returned to the Sundance Pond near the Cave and Basin wetlands about three to four years ago, creating two dams at the outflows to the Bow River.

The water levels have risen approximately 84 centimetres since 2021.

As a result of the beaver construction activities and rising water levels, Parks Canada has concerns about the risk of flooding to the Marsh loop trail, and potentially the commercial horse stables and Banff recreation grounds. The trail is popular for hiking and birding, but is also used by the Banff Trail Riders.

Parks Canada’s impact assessment review notes that the Marsh Loop trail probably would be affected by spring run-off, resulting in potential trail damage and closures for public safety if mitigations were not taken to lower water levels.

In addition, the federal agency has concerns that the water may break or flow over the levee, resulting in flooding of the adjacent road, Banff Trail Riders Stables, and/or Town of Banff Recreational Grounds.

“The water levels at Sundance Pond reached levels above historic norms this spring, placing pressure on the levee at the start of the Marsh Pond Loop,” said Justin Brisbane, a Parks Canada spokesperson for Banff National Park in a statement.

Bunyan, who is a retired resource conservation officer with Parks Canada, said the environmental assessment makes a few well reasoned arguments for lowering the water levels, but said the stated flooding threat to town recreation facilities is questionable.

He said the marsh area is a Zone 1 special preservation area for a reason, noting it is a unique ecological area that supports a number of rare species and provides some of the best birding opportunities in the Bow Valley.

While that designation does not preclude undertaking some management action such as modifying water levels, Bunyan said it certainly calls for a precautionary approach such as making smaller water adjustments and modifying as needed.

“This is Zone 1 special preservation and any management action taken there should be extremely conservative and taken with all the appropriate ecological precautions,” he said.

On May 6, Parks Canada installed temporary Clemson Levellers – simple, low-cost devices made largely from PVC pipe – in the existing beaver dams to reduce the flooding risk to the area.

The levellers are designed to allow water to flow through a dam, while preventing beavers from quickly repairing the dams. Beavers fix dams on the basis of sight, sound and feel of running water.

“This is a proven successful temporary solution intended to allow water to flow through the dams and restore water levels to their expected target,” said Brisbane.

“Following best practices for beaver dam management, removal of the keystone species was not considered as an option.”

Beavers are considered a keystone species.

In building dams to block streams to create ponds and wetlands, beavers provide many valuable services for the ecosystem, such as storage of water during droughts and floods, creation of habitat for many wildlife species, and improvement of water quality.

Peter Duck, BVN’s president, said members are concerned about damage to this special wildlife habitat at an obviously sensitive time of year and are upset about the loss of a special opportunity for visitors to observe and experience natural landscape processes.

“This was providing an opportunity to get close to nature,” Duck said.

“You would think this would be the place where we could make a little sacrifice in the interest of the ecosystem.”

Beavers started to recolonize areas around Banff after more than 200 elk were trapped and relocated between 1999 and 2002 as part of Parks Canada’s elk management strategy to reduce elk attacks and restore natural ecological process.

Back then, the big spike in the elk population around the townsite led to widespread environmental damage, destroying aspen and willow for example, which are considered key to the survival of songbirds and beavers.

“The beavers have been gone for a while but they are back doing what they would do; the willows have come back and the beaver are here to take advantage of that,” said Duck.

The marsh area is also important for nesting birds at this time of year, with Duck noting that birds pick their nesting sites based on the habitat characteristics around them.

“Now somebody has literally pulled the plug on them and in a matter of hours, that’s changed, it’s no longer the site they thought they had selected… so it’s probably a stressor on these species,” he said.

“There is a high likelihood that birds were going through their nesting behaviour at this time of year, they now have to readjust and figure out how to either reset themselves or maybe they’ve lost a window.”

Bunyan said the decision to remove the beaver dam also highlight’s BVN’s ongoing concerns about Parks Canada’s lack of a public-facing environmental assessment process.

It took the Outlook five days to get a copy of the impact assessment review, which is a public document, as part of a media approval process.

Bunyan said the assessment appears to have been written from primarily from an aquatics/fisheries perspective, which is important, but it had errors of omission from a nesting waterfowl perspective.

“If this EA had been posted, Parks would potentially have had significant public feedback on the issues of nesting timing and water levels,” he said.

"No one wants to or should need to review every routine Parks Canada decision. However this is a beloved and highly sensitive area where hearing input and concerns from locals and birding experts would have been valuable to all."

The Outlook contacted Parks Canada for an interview on Wednesday, May 11. The interview request was declined, and a statement was received on the afternoon of Tuesday (May 17).

Brisbane said a development review, including an options analysis and impact assessment was completed on the project which considered a number of valued ecological components, including fish species, amphibians, migratory birds, the beaver dam itself, amongst others.

“As a result of the review, it was determined that adverse effects were not anticipated, and a balance of water and wetland management with allowances for dynamic ecosystem processes to occur,” he said.