A new bioengineered approach for Wakamow

Lisa
Lisa Goudy
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Margaret Moran provides update with the valley's green river bank stabilization project

For years, erosion has been taking place along the Moose Jaw River.

The river bank was stable for many decades until the flood in spring 2011. The River Bank Stabilization Project was born as the first of its kind bioengineered river bank stabilization project in Saskatchewan at a cost of approximately $1.25 million.

"This type of bioengineered approach is the first of its kind in Western Canada," said Margaret Moran, CEO of Wakamow Valley Authority, "but this method has been used extensively in Ontario and also in Western U.S. - Wyoming, Montana and Colorado - very successful. It's less expensive than the traditional hard engineered approach. It's better for aquatic environment."

Funded by the Provincial Disaster Assistance Program (PDAP), the project is intended to stabilize the eroding river bank. Between flooding and ice jamming events in 2011, 2013 and 2015, considerable erosion started to threaten existing infrastructure like bridges and roads.

There are three main ways to slow bank erosion. Soil bioengineering system use living plant materials to provide some engineering function. Bioengineered systems integrate living materials with non-living structural elements for stabilization. Engineered systems use non-living materials in building structures.

"When engineered systems are used they are the strongest at the time of completion. However, over time they weaken and if they fail, they usually fail catastrophically," said Moran.

"Bioengineered methods are weakest when first completed, but with each passing year, the system gains strength as vegetation takes hold and roots integrate. Should a bioengineered fail, it is usually a gradual or slow failure."

Using 'next generation' bioengineered stream bank protection/restoration has "physical and ecological benefits," she said.

"It doesn't prevent nor does it contribute to flooding. It's flood neutral," said Moran. "It is a comprehensive approach to address isolated breaches in the river and it doesn't move the problem around to other areas."

In terms of soil bioengineering, one technique being used in Wakamow Valley is using live stakes where cuttings are placed into soft stream bank materials. The stakes provide mechanical stability while the root systems develop, she said, and in turn, it prevents further slope movement.

Work has been ongoing, including wood toe installation.

"We began to harvest wood for trees. The wood was harvested on-site in Wakamow Valley," said Moran. "Areas were chosen based on best practice for urban forestry management. All of the wood harvested was re-used in the project with the exception of rotten wood."

This spring, more than 1,700 new trees, shrubs and live stakes will be planted. New trees will be approximately two meters tall for a "good start to urban forest renewal," she said.

Other work includes rock spur with toe wood. Rock spur redirects flows away from the river bank while toe wood provides roughness, habitat and erosion protection. The bankfull bench provides flood relief and the point bar also provides flood relief as well as a depositional area.

"It's a really interesting process and it looks good, solid and the very kind of initiative that's required because we've all seen erosion damage that just keeps happening," said Coun. Don Mitchell. "Hopefully it will produce the results that are anticipated."

3 Facts: History of slowing bank erosion

1. Bioengineering has been used since 28 BC for dike repair in China. In Western Europe in the Middle Ages, willows were used to stabilize canal banks.

2. The use of bioengineering declined after the Industrial Revolution. Preference then changed to engineering systems.

3. Bioengineering has remained common in Europe and since the 1930s, it has seen a steady use in America as well.

Follow Lisa Goudy on Twitter @lisagoudy

Organizations: Wakamow Valley Authority

Geographic location: River Bank, Saskatchewan, Western Canada Ontario Western U.S. Wyoming Montana Colorado Wakamow Valley Western Europe China Middle Ages America

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