| "We’re helping to influence how other people are approaching habitat work in estuaries." | |
| Mike Graybill, South Slough National Estuarine Research Reserve |
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In the past, severe storms felled large trees and swept them into rivers, streams, estuaries, and even into the ocean, where they created a variety of natural habitats. For about the past hundred years, the number and size of trees being carried downstream has decreased, and the trees that do make it into the water are often removed to facilitate boating and prevent damage to dams, culverts, and other development.
Returning "large wood" to the natural system has become a well-known method for restoring stream habitat, but a National Estuarine Research Reserve in Oregon has recently used this method to restore juvenile salmon habitat and to develop an environmentally friendly canoe access ramp.
"Large wood in an estuary hasn’t been much on people’s radar screens," says Mike Graybill, manager of the South Slough National Estuarine Research Reserve in Coos Bay, Oregon. "We’re helping to influence how other people are approaching habitat work in estuaries."
Getting at the Root
For large wood structures in estuaries, "big trees with the root wads intact are most desirable," says Craig Cornu, the coordinator of monitoring programs at South Slough. "Whole trees placed in estuarine channels cause scour holes in the channel bottom to form, which combined with the tangle of roots and branches, provide important refuge for fish."
Graybill notes that the benefits of large trees vary depending on the environment. For instance, large trees provide food and hiding places for a variety of species in a stream or estuarine system and can absorb wave energy along the coast during storms, helping to prevent shoreline erosion.
The goal of large wood restoration is to facilitate and mimic the environment-specific natural processes.
In the estuarine environment, Graybill notes, trees would become stranded. While the trees can and do move around, the function in the estuary is most beneficial "when they are calm and experience relatively little movement."
Eight Months and Five Hours
A landslide in a local state park near the reserve severely damaged a road, and in order to relocate it, about 60 spruce trees were going to be harvested. The reserve was asked in February of 2004 if it had any beneficial use for the trees. The reserve selected 40 that were between 18 and 38 inches in diameter and averaged about 60 feet long—of adequate size for a large wood juvenile salmon habitat restoration project.
Partnering with the local watershed association, the reserve acquired grant funding and permits, as well as worked with the reserve’s advisory group of researchers and scientists to help finalize the design of the restoration project.
By October, the project was a go, and in five hours a large helicopter airlifted all 40 trees from the road construction project and placed them in their assigned locations in the restoration site.
"At $850 an hour to rent the helicopter and crew, it had to happen quickly," Cornu says.
Preserving Human Use
In the same area where the large wood restoration project was constructed, a fragile creek bank was often used as a site to launch canoes and kayaks into the shallow tidal waters of South Slough.
The reserve staff decided to use the same technology to "make sure that human uses were preserved along with habitat considerations," Graybill says.
In 2007, the reserve worked with a contractor to design a unique facility that stabilized two large hemlock logs protruding 20 feet into the creek to provide both easy access for paddlers and additional habitat for fish.
Export Potential
While reserve staff members immediately started seeing fish using the system for habitat, they know it will take a number of years of monitoring to determine the true success of the large wood restoration projects, Cornu says.
Graybill, however, is already happy with the results.
"The things we’re learning here have export potential," he says. "We’ve certainly seen that large wood projects have significant prospects in the Pacific Northwest."
He adds, "I wouldn’t have any reason to believe that large wood isn’t playing similar roles in other estuaries. I would encourage other coastal managers to take a look at large wood in their systems."
For more information on the South Slough National Estuarine Research Reserve’s "large wood" habitat restoration and canoe access projects, contact Mike Graybill at (541) 888-5558, or mike.graybill@state.or.us, or Craig Cornu at (541) 888-2581, or craig.cornu@state.or.us.
