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Like Louisiana, California has cities and farmland below the water level of its rivers. And since Hurricane Katrina, California has spent hundreds of millions of dollars repairing urban levees. However, the U.S. Army Corps of Engineers says there's another problem: vegetation. A long-standing Army Corps policy bans shrubs and trees along levees. They can be harmful. California faces the loss of federal levee funds if it does not comply.
Tamara Keith of member station KQED reports.
TAMARA KEITH: California's levees are covered with vegetation. James Sandner, chief of operations and readiness in the Sacramento office of the Army Corps of Engineers, says that's a concern. Roots could compromise the strength of levees. A tree could topple, creating a breach. He says after Katrina, the Corps changed its approach to levee maintenance.
Mr. JAMES SANDNER (Chief of Operations and Readiness, Army Corps of Engineers, Sacramento, California): We wanted to insure that the standards as they were described in our inspection checklist were followed in a much more rigorous manner than they had in the past.
KEITH: And that new emphasis has California officials worried about the fiscal and environmental implications. Gary Hobgood is an environmental scientist with the California Department of Fish and Game. He's parked his white, state-issued pick-up truck on the crown of a levee on the west side of the Sacramento River.
Mr. GARY HOBGOOD (Environmental Scientist, California Department of Fish and Game): So as you look out there and along this berm...
KEITH: Hobgood points to a thick shock of trees and shrubs growing on the side of the levee. The vegetation along California's levees is the last remaining sliver of what was once a Riparian forest. He says its critical habitat for a who's who of endangered species.
Mr. HOBGOOD: Swenson hawk, bank swallow, a yellow-built cuckoo, 10 listed fish species, giant garter snake. If we were to lose this vegetation, those species would take a big hit.
KEITH: But this isn't just about habitat. It's about safety, about priorities, says Les Harter, deputy director for public safety at the California Department of Water Resources.
Mr. LES HARDER (Deputy Director for Public Safety and Business Operations, California Department of Water Resources): We don't want to spend hundreds of millions of dollars focused on clearing vegetation when we have clear deficiencies on the levees. We have underseepage problems, we have overtopping issues, we have erosion issues. We haven't had a failure because a tree fell down.
KEITH: Harder and others say they want the Army Corps to make decisions about vegetation on levees based on solid science and engineering. At the hydraulic lab at the University of California, Davis, researchers are trying to produce hard data. A pump pushes water into a massive steel plume designed to replicate a floodway, complete with shrubs.
Mr. STEFAN LORENZATO (Research Coordinator, California Department of Water Resources): You know, they're leaning over now, you can see a little bit of a current on them.
KEITH: Stefan Lorenzato is coordinating the research. This study is examining how different plants affect water flow and erosion. Lorenzato says the plants are reducing soil erosion.
Mr. LORENZATO: The test we're conducting seem to be showing that regardless of what happens on the habitat side, there's a reason you use plants just for structural integrity.
KEITH: The Army Corps' James Sandner says his agency is open to new findings and isn't looking for a fight with the state.
Mr. SANDNER: We should be able to work together in a collaborative manner, to come up with decisions that make sense for public safety and also allow for preservation and management of some of this Riparian habitat.
KEITH: The Army Corps is expected to release a final rule on vegetation later this year. California officials say they realize some plants will likely have to go, but they're hoping for flexibility from the Corps.
For NPR News, I'm Tamara Keith in Sacramento.
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