Habitat benches and salmon skylights help fish feel at home.

By Katharine Logan

Before Seattle grew up on its shores, Elliott Bay was a bluff-backed beach, with intertidal marshes and mudflats providing a complex and varied habitat for birds, fish, and marine invertebrates. Its sloping beaches offered salmon a safe passage through shallow waters, with plenty to eat along the way.

The growth of Seattle changed that. The developing city filled and leveled its waterfront behind a seawall built on densely spaced and creosote-blackened pilings. Deep, dark, and toxic, the urban shoreline repels migrating salmon out into the bay on a difficult journey where they become easy prey for other fish and marine mammals.

Now, aspart of an ASLA award-winning redevelopment plan led by James Corner Field Operations, the replacement of the Elliott Bay Seawall is under way. And as details of the design for the new seawall emerge, it’s clear that it’s not just the people of Seattle who will benefit from the waterfront revitalization. The iconic Pacific salmon, central to the ecology and historic culture of the Pacific Northwest—and now struggling to survive the combined threats of overfishing and habitat loss—will enjoy some relief as they migrate along this redesigned stretch of the city’s edge.

With the need to replace the aging seawall comes a rare opportunity to encourage the salmon back in to shore. “The salmon runs—their highways—have been seriously disrupted by industrial development of the waterfront,” says Tatiana Choulika, ASLA, principal at Field Operations and design lead on the project. “Their situation is dire.”

Field Operations’s design for the new seawall re-creates the shallow waters salmon prefer, raising the seabed with a habitat bench. The bench, now under construction, consists of sand and gravel cushions stacked up in a narrow band along the base of the wall. The bench widens out into larger shelves near Pioneer Square and the Seattle Aquarium and is intended eventually to link to a beach at the Olympic Sculpture Park.

To allow sunlight to penetrate these new shallows, so that the salmon can see and plants can grow, a cantilevered promenade along the top of the seawall will be surfaced with a grid of glass blocks all along its length. The grid will provide a nearly 20 percent glazed area to act as skylights for the salmon.

Between the skylights above and the bench below, the wall itself will be surfaced with textured panels so that algae and aquatic life can attach and provide the fish with safe feeding grounds. The artist-designed panels take inspiration for their textures from the natural environment at each tide level of the wall, referencing bull kelp, seaweed, sea stars, anemone, mussels, barnacles, and lichen.

Construction of phase one is scheduled for completion in 2016.

Katharine Logan is a British Columbia-based contributing editor for GreenSource.

Photo Credit: James Corner Field Operations.