Better Edges for Eels

On a living shoreline in Ontario, Canada, Seferian Design Group balances designing for erosion and endangered species.

By Timothy A. Schuler

The hybrid shoreline mitigates erosion while also enhancing terrestrial and aquatic habitat. Image courtesy Seferian Design Group.

On the northern shore of Lake Ontario, 25 miles outside Toronto, a quarter mile of once-eroding lakefront is a case study in resilient design for the Great Lakes. Although at first glance it may not look as green or vegetated—as alive—as other so-called living shorelines, the new shoreline was planned and built around the needs of multiple vulnerable wildlife species and offers vital refugia for still others.

The stretch of shoreline belongs to Appleby College, a private preparatory school in Oakville, Ontario. Its largely natural shoreline was eroding at an alarming rate, battered by increased wave action caused by historically high lake levels and severed from natural replenishment cycles by shoreline hardening projects nearby. “They’d done surveying every couple of years, and in some areas, five, six meters of shoreline were just gone,” says Brad Smith, ASLA, a senior landscape architect at Seferian Design Group in nearby Burlington, Ontario, which was hired to help address the problem after a more typical hardening plan was scrapped. “The conservation authority came back and said, ‘We want something greener, softer, more dynamic.’”

The newly engineered shoreline employs both natural and seminatural shoreline strategies to protect the property from further erosion while also enhancing existing terrestrial and aquatic habitat. Interventions include the reconstruction of an armor stone revetment (a “hard” solution that nonetheless permits water intrusion and vegetation growth in the gaps between stones) and stretches of cobblestone beach that mimic historic conditions. An all-native plant palette and a nine-foot-wide no-mow zone at the crest of the bank are designed to provide additional stabilization and foraging opportunities.

Image courtesy Seferian Design Group.

As a living shoreline, it’s experimental, blending traditional and ecological approaches. “We ran almost the full gamut of coastal solutions,” says Chris Moon, a water resources engineer at Ecosystem Recovery Inc., a consultant on the project.

Notably, the shoreline was designed and built around vulnerable bird and fish populations, including a group of northern rough-winged swallows, which had taken up residence in the exposed face of the eroded bank. Although the swallow is not endangered, bank swallows, which built the nests, are listed as threatened under Canada’s Species at Risk Act. The design team preserved the nests, creating a cobblestone beach below the bank to mitigate wave action, taking care to keep the rock at a distance to prevent predators from reaching the eggs and young.

Another threatened species at the site was the American eel, a native freshwater fish that is endangered in Ontario. The American eel’s life cycle is the inverse of salmon: They are born in the Atlantic’s Sargasso Sea, swim upstream to feed, and then return to saltwater environments to spawn. In Ontario, American eel populations have been decimated by overfishing, habitat loss, and deadly hydroelectric turbines and have been reduced to just 1 percent of their historic numbers. At Appleby, the existing eel habitat was carefully preserved and expanded, and construction activities were timed around the eel’s life cycle.Sarah Mainguy, a senior ecologist at North-South Environmental, a consultant on the project, says the project’s hybrid nature makes it a potential model for other Great Lakes sites, which will continue to experience erratic conditions in coming years. Like all dynamic systems, however, the approach requires monitoring and maintenance. “If you’re going to go down the path of using that kind of approach, you have to know that it’s not just set it and forget it,” Moon says. “You’re gonna move it around, you might have to supplement it—but it’s effective.”

Historically high lake levels had left the school with a rapidly disappearing shoreline. Image courtesy Seferian Design Group.

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