TEAM RESTORING RIVER’S BANK
City and province taking cues from Mother Nature in use of alternatives to stop erosion
When Chris Hugenholtz and a team of university researchers started mapping sections of the Elbow River in 2012, he had no idea his findings would act as before and after snapshots of Mother Nature’s awesome power.
The team was using an eight-kilometre stretch of river near Redwood Meadows, west of Calgary, as a test site to see how they could use drones to create 3-D maps of fish habitats.
One year after the project began, Hugenholtz said his research took a turn when the southern Alberta flood came along and dramatically changed both the river’s course and his findings.
“It’s an interesting part of the river because right where we use the drones, Redwood Meadows almost had a breach ... so there was a lot of change that happened, and it was a very kind of violent event right in that location.”
Hugenholtz said the flood caused “dramatic changes” to that section of the Elbow due to significant erosion; it widened the river considerably and straightened out the river’s course.
Alberta Environment and Parks said the flood had a minimal impact on the province’s sport fish populations. In some areas, such as parts of the Bow River through Calgary, the flood actually improved spawning conditions for brown trout. The rushing waters helped clear away debris, rocks and sediment, which can make tough work for female trout to dig out spots to lay their eggs.
The flood also left behind some natural flood mitigation measures by changing the geological makeup of the river bank. Smaller rocks and gravel were washed away leaving very larger boulders in their place, which will help protect the banks from future floods.
“We’re going to need another really big event to exert a lot of influence in changing the river because, in a way, it kind of armoured itself against low-magnitude events,” Hugenholtz said.
Bioengineering — like the natural rock deposits Hugenholtz observed in the Redwood Meadows area — has been playing a big role in flood mitigation projects downstream from the Rockies, in Calgary and in many parts of southern Alberta.
One such initiative is the Bioengineering Demonstration & Education Project on the banks of the Bow River in Inglewood, said David DePape, senior manager with Alberta Environment and Park’s Fishes (Fisheries Habitat Enhancement and Sustainability) program. He’s been working with the City of Calgary on the project since March and the team has been repairing the riverbank, which was washed away about six to nine metres.
Team members use plant species native to southern Alberta and construction techniques that have a minimal environmental impact to improve the bank.
DePape said the most significant harm to the environment wasn’t caused by the water, but rather by work done to repair damage immediately following and during the flood.
“We had large excavators, trackhoes (and) rail cars dumping (rocks) in order to get ahead of and provide immediate protection to those highly eroded banks or displaced high pressure gas pipelines that often run under rivers and streams,” DePape said. “And that work had to happen, but there are consequences to that emergency work. And that’s what we’re addressing now.”
Many fish species and amphibians in Alberta, like the protected northern leopard frog, were temporarily displaced because of the flood.
DePape said the ministry helped recover thousands of stranded fish from “some interesting places” around Calgary, but added these animals have been around for 300 to 400 million years and know how to adapt to dramatic changes in habitat.
“A lot of folks are of the mistaken belief that these sorts of natural events have significant and longlasting effects on fisheries and wildlife population,” he said. However, “those critters and fish, to a large degree, found their way back as flow returned to a semblance of normality.”
Normal conditions are indeed returning.
Timber, soil and native vegetation have been used to create about a dozen six-metre-long crib walls along the bank to safeguard against erosion and create an overhang, ideal for trout habitat.
The river’s edge has been contoured to a slope where the bank previously had a steep cliff face. The project, which is only one of 11 under the Fishes program, is also using retaining walls made with bundles of plant species like cottonwoods, poplar and alder to reinforce the banks.
Frank Frigo, with the city’s water resources department, said the city used some bioengineering techniques in projects along the river banks prior to the 2013 flood.
Those bioengineering sites held up better, in terms of experiencing decreased erosion, when compared to areas that used more traditional construction techniques, he said.
“This is really where water resources (are) evolving too, and that recognition that nature has evolved some very self-healing processes,” Frigo said. “The last three decades have been a really, really interesting time. We’ve reformed and reshaped our understanding of nature and really learned to work in concert with it.”
DePape said he hopes to “set a standard for industry” with the project by testing the effectiveness of nature-friendly alternatives to standard construction techniques to stop erosion, such as using concrete and stone to protect the banks.
While these techniques are fairly new to Calgary, DePape says bioengineering has been gaining popularity in Europe and in B.C. The project has already piqued the interest of engineers from France and Germany who have taken tours of the site.
Along with repairing the washed-out pathways, improving the riverbanks and repairing fish habitat, the project will serve as an interpretive centre on the benefits of bioengineering.
There are even plans for construction of river overhangs and placement of educational signage on the bus rapid transit bridge being built next to the project, slated for completion in 2019.
The province is also using bioengineering for rehabilitation and reclamation projects in Alberta’s national parks and backcountry recreation areas.
Andun Jevne, program manager with Alberta Environment and Park’s backcountry trails flood rehab program, said some 5,300 kilometres of backcountry trails were surveyed for post-flood damage. About 140 bridges and more than 500 kilometres of trails needed repairs.
"(Bioengineering) reduces the need for some of those expensive hard engineering options,” Jevne said. “For us it was twofold: We see it as an effective way of reducing erosion and stabilizing banks, but it’s also a cost-effective way (of improving erosion control) because it’s really hard to get that type of heavy material way back in the back country.”
Jevne noted there are only 11 projects left in the $11.5 million program’s mandate and a fair share of the credit for repairing the province’s trails goes to user groups, stakeholders and volunteers who donated time and effort to the projects.
“We had something like 7,000 hours of volunteer contribution into the program, and that is kind of the take away for me.”