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Scientists give shoreline primer

More than half of Bainbridge’s roughly 50 miles of shoreline are armored with artificial bulkheads.  - Brad Camp/File Photo
More than half of Bainbridge’s roughly 50 miles of shoreline are armored with artificial bulkheads.
— image credit: Brad Camp/File Photo

Photos of tumor-infested sole fish in Eagle Harbor were all it took to kindle environmental fervor on Bainbridge 20 years ago.

The outcry led to a massive project to cap sediments contaminated by the Wyckoff creosote plant, an effort that continues at the Eagle Harbor Superfund site. It was an easy case of tracking an environmental impact to a human cause, said Casey Rice, biologist for the National Oceanographic and Atmospheric Administration.

“At the beginning of the environmental movement, these point sources were one of the first things we began to understand,” Rice said.

But Rice, joined by Tom Mumford of the state Department of Natural Resources, and Jim Brennan of Washington Sea Grant, said most damage wreaked on Puget Sound shoreline habitat by human activity today is more subtle, and its root causes are far harder to pinpoint.

The three scientists spoke to a crowd of 80 at IslandWood Thursday night, as part of a “Island on the Edge” forum, sponsored by Bainbridge Alliance for Puget Sound. The discussion was aimed at informing citizens about the science surrounding both local and regional shoreline initiatives.

Following legal prodding from the Suquamish Tribe, the City of Bainbridge is now in the midst of revising its Critical Areas Ordinance to include protections for nearshore habitat, which could mean tighter regulations on shoreline structures and buffers.

Meanwhile the state-mandated Puget Sound Partnership is tackling environmental degradation throughout Puget Sound.

Brennan, a University of Washington biologist and island resident, laid out the physical nature of the shoreline environment and how human activity can disrupt its functions.

The band of vegetated bank above beaches, called the riparian zone, is critical as both a filter for contaminated runoff as well as a protective barrier for humans, he said.

“There’s a human safety aspect as well,” he said. “Leaving a buffer, a setback from storm surge, is really important.”

The banks slowly erode at the base, feeding sediment onto beaches below, where spawning foraging fish lay eggs in the gravel. The shallow waters of the nearshore environment, which ranges from salt marsh to rugged outcroppings, is home to a host of marine species that thrive with sunlight and abundant food. According to Brennan, land-based insects make up 50 percent of the diet for juvenile chinook salmon, which migrate along the shorelines.

Human activity along banks can throw discord into the nearshore system in a number of ways, he said. The clearing of upland vegetation can damage the natural filtration of the banks and lead to erosion, while bulkheads and other shoreline armor can disrupt drainage and actually destabilize slopes, while accelerating the scouring of beaches below. The most important thing people can do is to leave space along undeveloped shorelines, Brennan said.

“Giving some space for the system to breathe and work is important for us, and important for Puget Sound,” he said.

Marine plant species, which form the base of the nearshore ecosystem, are highly susceptible to development, said Mumford.

“Unlike salmon, which, if they don’t like it they can leave, plants have to stick around,” he said.

The contribution of Puget Sound’s marine plants, which include 600 seaweed species and a hand full of flowering plants like eelgrass is often overlooked, Mumford said. But they provide both a physical home for other organisms, while leeching carbon into the ecosystem.

Plant growth can be over-stimulated by an influx of nitrogen and other nutrients from inland sewage systems and fertilizer runoff he said. Shoreline structures can physically displace plant beds, or shade them from the sun.

Both are issues on Bainbridge and around the Sound.

“There’s nothing unique about Bainbridge Island,” Mumford said. “It’s fairly normal, the problems you are facing are fairly widespread.”

Many residents at the discussion said they were skeptical of the “best available science” they had heard as the justification for local projects over the years. Others said shoreline protection should begin with stricter enforcement of codes already in place.

John Anderson, who owns a home on the shoreline of Eagle Harbor, said his house was located 50 feet from a bulkhead built into his property long before he bought it. He said he understood that the bulkhead could be environmentally damaging, but with high levels of ferry and boat traffic in the harbor, he wouldn’t feel safe taking the wall down now.

Any new regulations, he said, need to take into account that most Bainbridge shoreline owners already have structures on their property.

“The regulations put in place will impact a very specific group of people,” he said.

Community Events, April 2014

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