SEATTLE — Trees, shrubs and other vegetation hugging miles of levees in Puget Sound provide shade and key habitat for many of the Northwest’s struggling salmon. But hundreds of trees have been cut down in recent years to satisfy the Army Corps of Engineers, which says vegetation compromises levees that prevent flooding.
With many more flagged for removal, communities are fighting to save some or all of the trees and brush — including willows in the Seattle area, Ponderosa pines in Coeur d’Alene, Idaho, and oaks and cottonwoods in California’s Central Valley. They say vegetation in some cases can actually reinforce levees.
Last month, the state of California sued the corps, saying it didn’t follow federal environmental laws when it required the removal of most trees and shrubs on federal levees. Environmental groups have also sued over the corps’ policy to preserve levee vegetation in Idaho and California.
Meanwhile, the Puget Sound Partnership, a state agency, has been working with local and federal agencies and the corps to find an alternative that would allow levee managers such as King, Whatcom and Pierce counties to maintain some vegetation along the levees while still ensuring they protect people.
“We’re confident that trees on levees can be safe,” said Mark Isaacson, director of King County’s Water and Land Resources Division. “We have not observed trees causing damage to levees.”
In recent years, the county reluctantly cut down more than 400 trees and shrubs along the lower Green River south of Seattle to meet corps standards and to avoid losing millions of federal dollars for levee repairs. At the same time state laws required it to spend millions to balance out that loss of salmon habitat elsewhere.
The corps says its standards keep people safe, reduces flood risk and are based on the best available information. Undesirable vegetation can undermine the structural performance of levees, block visibility for inspections and hinder flood fighting, it says. A two-year corps study found that trees could strengthen levees in some cases and weaken them in others, depending on soil, climate and other factors. However, the corps says it will err on the side of caution for public safety in areas of uncertainty.
“We want safe levees, bottom line,” said Patricia Graesser, a spokeswoman with the corps’ Seattle district, which covers Washington, northern Idaho and western Montana. Nationwide, the corps has authority over about 14,700 miles of levees in its levee rehabilitation program.
“We have salmon swimming up against our levees where other parts of the country do not,” Graesser said of the Northwest. “What we’re trying to do is: What can we do to keep levees safe and also meet requirements under ESA (Endangered Species Act) and (tribal) treaty trust?”
A corps policy currently being finalized allows exceptions to the national standard, which calls for a vegetation-free zone within 15-feet of levees. But local, state and tribal officials say the process is too costly and impractical. The corps says the collaborative approach will allow sponsors to determine early in the process whether to seek a variance.
Steve Landino, Washington state habitat director for the National Marine Fisheries Service, worried the process would be so burdensome that local levee managers will cut down the trees to comply. “That’s not going to be good for fish,” he said.
Writing to the corps in April, federal wildlife and fisheries experts said ripping out vegetation on or near levees could further harm habitat for Northwest salmon and steelhead already on the brink. American Indian tribes warned the policy risks violating tribal fishing rights. And local levee districts urged the corps to allow for regional exceptions to its national policy.
“The fact is that the science doesn’t show that vegetation weakens levees,” said Lisa Belenky, senior staff attorney with the Center for Biological Diversity, who along with Friends of the River and Defenders of Wildlife sued the corps last year over the policy in California. “It’s very dependent on the ecosystem of the area and the climate in that area.”
In Coeur d’Alene, city engineer Gordon Dobler said the city is trying to retain as many ponderosa pines and other trees along its levees as possible, though they may not be able save them all. It may do so by seeking a third-party certification that the levees are structurally sound, he said.
Isaacson said King County and others are caught between two conflicting federal mandates: remove riverside habitat and risk violating federal environmental laws, or keep the vegetation and risk losing federal money for levee repairs.
“We’re in a very difficult position,” he said. “It’s really a conundrum that everyone understands clearly, and they want to fix this.”