The restoration of the landscapes after removal of the Elwha and Glines Canyon dams and their associated reservoirs is more than just planting a few trees, shrubs and grasses.
Since 2000, the Lower Elwha Klallam Tribe and Olympic National Park have been collecting millions of seeds from native plants in the river valley. From those seeds, crews expect to plant more than 400,000 plants throughout nearly 800 acres of new lands exposed by the dewatering of the reservoirs Lake Mills and Lake Aldwell.
The seeds are being stored at the park’s Matt Albright Native Plant Center in Agnew and at Silvaseed Company in Roy, WA. The tribe and park also have worked with commercial nurseries around the Pacific Northwest to supplement the production of native trees, shrubs and grasses.
“While the dams are coming down, we’re hoping to get a head start on the vegetation establishing itself,” said Josh Chenoweth, a botanist with the park. “So far at Lake Mills, we have 25,000 plants in the ground.”
The site is lacking developed soils. Instead, revegetation must occur on deep layers of inorganic silt and clay or on terraces of sand and gravel that have accumulated in the reservoirs over the last 80-100 years. Vegetation to be planted includes Douglas-fir, twinberry, nootka rose, cedar, Suksdorf’s wormwood and various types of willows, in addition to dozens of other grasses, trees and shrubs.
“We’re trying a variety of planting methods, from bare roots to container plants,” Chenoweth said. “As we plant, we’re letting the site teach us what will work. We’ll see what survives, and what doesn’t, and go from there.”
The crews started planting the Mills site in November 2011 soon after the Glines Canyon dam deconstruction started in September 2011. Revegetation of the former Aldwell reservoir won’t start until the fall of 2012. The overall revegetation work is expected to be completed by 2018.