Updating a culvert brings the salmon back to a Langley creek.

Close your eyes and imagine the kind of urban development that threatens wildlife habitat. Chances are, you see a lot of concrete and steel. But as several B.C. stewardship projects are demonstrating, the very materials that often endanger the natural environment can sometimes help to support wild salmon.

In Langley Township, a series of impassable culverts and crossings near Highway 1 had long prevented wild salmon from travelling up Yorkson Creek to their native spawning grounds.  It’s tough work swimming upstream. Eroded outfalls, a lack of resting places (or baffles), and blasting water pressure made it impossible for salmon to complete the journey.

Thanks to a group of volunteers, engineers and fabricators, two of these old culverts were recently replaced with salmon-friendly, 12-by-7-foot precast concrete box culverts. Concrete baffles that resemble ladder-like ribs were also added to the new culvert streambeds, giving salmon a much-needed place to rest.

The details required collaboration between engineers, designers and watershed experts, but the result is that salmon can now travel safely underneath a busy highway without exposure to predators, off-leash pets or urban dangers – and now an increasing number of Coho in Yorkson Creek are doing exactly that.

Light at the end of the culvert?

Using concrete to cast baffles and fish passages is “an idea that engineers are becoming more aware of when they’re working in sensitive habitat,” says Joel Shimozawa, a technical marketing engineer for Langley Concrete Group in Chilliwack, which installed the new culverts. “It’s also a building material that will last a long time.”

According to Natal Cicuto, chair of the Yorkson Watershed Enhancement Society and a self-described “fish whisperer,” baffles create natural pools and nests inside the streambed gravel. Add in quality water with enough depth, a 1-3 per cent slope, and good gravel coverage, and you have the three main criteria required for salmon to successfully migrate and spawn.

“In nature, salmon have trees and logs and rocks that they can hide amongst,” says Cicuto. Human-made (and salmon-friendly) culverts and baffle systems mimic those natural structures.

When concrete is too costly or a culvert is in good shape, steel can also create a better salmon passageway – even if it’s a temporary solution. Under the Dollarton Highway in North Vancouver, for example, watershed stewards recently worked with engineers and stakeholders to install custom stainless steel baffles that fit inside a corrugated culvert. The system replicates a series of cascading freshwater pools where salmon naturally migrate. It might not be a tree-lined estuary, but re-wilding materials like concrete and steel can give wild salmon a fighting chance in an urban landscape.