Anchor QEA was featured in Encyclopedia of Puget Sound: “New Seattle Seawall Improves Migratory Pathway for Young Salmon.”

Anchor QEA was recently featured in Encyclopedia of Puget Sound’s recent article, “New Seattle Seawall Improves Migratory Pathway for Young Salmon.”

The new highway for salmon and enhanced seawall has been called the largest eco-engineering project of its kind, boosting the chances of survival for young salmon as they migrate through a treacherous section of waterfront on their way to the ocean.

Anchor QEA partners with the University of Washington in the successful restoration and continued monitoring of Seattle’s downtown shoreline, transforming it into a thriving ecosystem.

Read the full article here: https://www.eopugetsound.org/magazine/IS/seawall 

 

Nobody with an understanding of marine life would describe Seattle’s downtown shoreline as a thriving ecosystem. More than a hundred years of city development have left its tidelands covered in fill, flanked with concrete and overshadowed by industrial piers.

Yet salmon habitat seems to be improving there, scientists say, thanks to new features installed during replacement of the downtown seawall.

The enhanced seawall, which has been called the largest eco-engineering project of its kind, may be boosting the fitness and chances of survival for young salmon as they migrate through a treacherous section of waterfront on their way to the ocean.

Instead of encountering a barren slab of concrete, salmon can now swim across a “bench” in front of the seawall. The bench forms a narrow strip of intertidal habitat, effectively providing a shallow-water pathway for juvenile salmon. Glass blocks in the sidewalk above the seawall allow light to penetrate to the water below, and a rough surface on the wall itself has horizontal shelves to encourage the growth of algae and invertebrates.

New scientific findings about marine organisms growing on or near the seawall plus behavioral changes in young salmon swimming through the area suggest a real payoff from these enhancements, which added about 2 percent to the cost of the $410-million seawall.

“I am very satisfied with the result,” said Jeff Cordell, a researcher with the University of Washington’s School of Aquatic and Fishery Sciences who has been involved with the project from the start. “What we are encouraged about is that fish seem to be using habitat where they didn’t before.”

Some people say these new findings could lead to discussions, strategies and possibly regulations to reduce the ongoing damage in other locations where shoreline armoring remains a necessity. The Washington Legislature has commissioned an investigation to determine if future shoreline construction should be required to enhance, not just protect, habitat — thus going beyond the current “no-net-loss” standard to create “net ecological gain.”

More than a vertical wall

For close to a century, the seawall along Seattle’s sprawling waterfront has protected waterfront buildings and other structures from the pounding waves of Elliott Bay. For all practical purposes, the seawall did its job well. But after the 2001 Nisqually earthquake, engineers examined the integrity of the structure. They found, among other problems, that wood-boring invertebrates had weakened wooden components of the seawall, raising concerns that the wall could collapse in the next big earthquake.

Until it came time to replace the seawall, few people gave much thought to the tiny migrating salmon working their way among the pilings, searching for food and doing their best to avoid predators along Seattle’s waterfront.

Throughout Puget Sound, marine biologists have long described the environmental damage caused by seawalls, bulkheads and other shoreline armoring. Coastal geologists estimate that wood, rock or concrete structures have displaced natural habitat along 29 percent of the Sound’s 2,500 miles of shoreline.

In designing the new Seattle seawall, a variety of experts, including Cordell, began asking questions: Could something be built to offer fish better protection from predators and perhaps a little more food to eat while still holding back the land? In other words, could a functioning structure provide improved habitat with less hazard?

Under natural conditions, juvenile salmon tend to stay in shallow waters along the shoreline to avoid larger predators as they search for food. One of the major problems caused by shoreline armoring is that shallow water disappears when the tide comes in. In fact, where tidelands have been filled in — such as in older downtown and industrial areas — the water may never leave the wall.

In building the new 3,100-foot section of Seattle seawall from the Colman Dock ferry terminal north to the Seattle Aquarium, construction crews created a platform, or bench, in the front of the wall. The top of the bench was intentionally placed at an intertidal elevation — meaning the bench is covered with water at high tide and exposed at low tide, forming a shallow-water habitat during a portion of each day.

The bench was built by stacking mesh bags of quarry rocks, nicknamed rock mattresses, between the new wall and a sheet-pile barrier. The sheet pile, a series of interlocking steel plates, was installed initially to keep water out of the construction site. It was later cut down to form the front of the bench.

To facilitate construction, the new seawall was located 10 to 15 feet farther back from the water than the old one. The sidewalk along the waterfront was then built in cantilever fashion over the wall and above the new intertidal bench. To counteract the effects of the sidewalk shadow, glass blocks were installed in the walkway to transmit light to the bench and water below.

The new seawall also features a series of horizontal shelves attached at various locations, along with lots of crevices, to encourage the growth of seaweeds, invertebrates and other marine organisms.

“The goals,” said Cordell, “were to create an intertidal migratory corridor for juvenile salmon and to increase the nearshore ecosystem.”

New highway for salmon

The Seattle seawall lies on the migratory pathway used by juvenile Chinook, chum, pink and coho salmon making their way to the Pacific Ocean from the Duwamish River and its more-productive upstream reaches bearing the name Green River. Young salmon from more distant rivers to the south, such as the Puyallup and Nisqually, may also find themselves in the clutter of piers and pilings along the urban waterfront.

Before the seawall reconstruction, researchers in snorkeling gear watched for salmon during their migration from March through August. They found much higher densities of young salmon between the piers than in the shadows under the piers.

Scientists have long observed that salmon are hesitant to go under docks, floats and other overwater structures during daytime hours, often stopping at the sharp lines of shadow.

“They don’t like shade lines,” Cordell explained, noting that juvenile salmon tend to stay in the sunlight because their success in finding food is dependent on their ability to see. To avoid the shade of the Seattle piers, some fish even travel through more treacherous deep water, going out and around the piers.

The new seawall with its cantilevered sidewalk embedded with glass blocks altered the nearshore area in some critical ways. Light passing through the glass blocks increased visibility under the piers, where previously light levels were very low. At the same time, moving the seawall farther back and under the sidewalk resulted in a loss of light at the water’s edge that was only partially compensated with the glass blocks.

After construction, researchers observed a notable increase in feeding behaviors under the piers, where the fish had never been known to feed before, according to Cordell. Between the piers, the fish continued to forage much as before, resulting in a more consistent feeding pattern as the fish swam from pier to pier during their migration along the shoreline.

Seawall inspires new thinking

The new Seattle seawall has been touted as proof that salmon habitat can be improved, even in the most degraded urban environment. For many, the project offers new prospects for improving salmon habitat on just about any shoreline in Puget Sound.

So far, the big push by cities and counties has been to get people to remove old bulkheads on shorelines where the wave energy is low and hard armoring is not really needed. So-called “soft shore” protections — including logs and rocks anchored to the beach in a natural configuration — can help reduce shoreline erosion without upsetting the ecosystem.

For publicly owned shorelines, local governments have been using state and federal grants along with their own resources to replace bulkheads with soft-shore structures throughout Puget Sound. For private property owners, so-called “Shore Friendly” programs offer encouragement and sometimes financial and technical support to remove old bulkheads.

The primary message of Shore Friendly is that most shoreline properties in Puget Sound do not need the protection of bulkheads. The program acknowledges that armoring may be necessary where homes were built right up to the shoreline years ago before modern regulations outlawed such construction.

Under the Shoreline Management Act, rules call on property owners to consider the least harmful alternatives, yet many local governments have been allowing the replacement of bulkheads without questioning the environmental consequences, according to Tim Trohimovich of Futurewise, an environmental group that has studied the role of government in protecting shorelines.

A key provision of the Washington Administrative Code states, “The replacement structure should be designed, located, sized, and constructed to assure no net loss of ecological functions.”

The no-net-loss standard allows for environmental mitigation elsewhere along the shore to make up for ecological damage caused by construction.

Trohimovich says many local governments could do a better job of exercising their authorities to ensure “no net loss” — either by strengthening local regulations or by enforcing current rules. The Seattle seawall project provides an example of finding ways to improve habitat even at difficult sites, he said.

Meanwhile, the governor’s Southern Resident Killer Whale Task Force has concluded that the no-net-loss standard may not be strong enough to bring about significant environmental restoration. The task force, charged with finding ways to keep Puget Sound’s orcas from going extinct, says the state needs to adopt a policy of “net ecological gain” to improve salmon habitat and save the whales.

Legislation that would have required a builder or developer to improve ecological functions as part of any construction project never made it out of committee this year. Instead, the Legislature approved a $256,000 study to consider the burdens and implications of a net-ecological-gain requirement.

The bottom line is that habitat improvements are coming too slowly to help salmon and killer whales, said Mindy Roberts, a member of the orca task force and director of Puget Sound programs at Washington Environmental Council.

“That Seattle seawall project was what we had in mind behind the idea of net ecological gain,” Roberts said. “The goal is not to restore a site to pristine condition but to leave it in better shape for future generations.”

Opponents of the bill that would have required net ecological gain argue that this very concept runs counter to individual property rights, as prescribed by state law and the U.S. Constitution. To require mitigation, they argue, government must show a clear connection, or nexus, to the environmental damage caused by the development. Builders should not have to pay for environmental damage caused by past practices that were legal at the time, they say.

In funding the new study, the Legislature called for an assessment of the legal issues surrounding net ecological gain, a description of how to measure such gain, and an analysis of how the new standard might apply to the Shoreline Management Act, the Growth Management Act and other environmental laws.

The Washington Academy of Sciences was assigned the task of determining what kinds of environmental protections may be missing from current state law and where the no-net-loss standard may be falling short. A consultant is being hired to review legal and policy matters.