SACRAMENTO — The federal government is pressing forward with a policy that could require trees to be stripped from California levees, eliminating what shade and wildlife habitat remain along the state's rivers, and costing billions of dollars.
An interim agreement appears likely to shield the state's levee habitat until 2012. But after that the U.S. Army Corps of Engineers could impose the new rules, which would allow nothing but short grass on most Central Valley levees.
Levee maintenance agencies can seek an exemption — called a variance — but even that could save trees only on the lower two-thirds of a levee's face on the water side. All other surfaces of the levee must be cleared.
"The proposed policy will likely have devastating environmental consequences," Mark Cowin and John McCamman, directors of the state Water Resources and Fish and Game departments, told the corps in a joint letter April 15. "We urge the corps to cease implementation of this new policy and procedures."
The Army Corps believes trees cause floods: by ripping out whole sections of a levee should they fall over in a storm, or by creating a path for water to seep through a levee via their roots.
But there is little proof of this, especially in California, where storm conditions differ from those in the hurricane-plagued South. In fact, research suggests trees strengthen levees by binding the soil together.
"We are not aware of any levee failures in the Central Valley that were caused by woody vegetation," Cowin and McCamman wrote.
Pete Rabbon, director of the Army Corps National Flood Risk Management Program said the corps is doing more research but stands behind its policy.
"We have our standards as they exist now," he said, "and we cannot change those standards unless we have something that shows us that change is an improvement."
The corps requires detailed surveys of levees before it will consider a variance.
If a region fails to comply, it could lose federal aid in the event of a flood, and may lose eligibility for federal flood insurance.
Removing trees would not only be environmentally destructive, it would be expensive, state officials said. "It's so expensive, it's really difficult to see how anyone could do it," said Gary Hobgood, an environmental scientist at the California Department of Fish and Game.
In a 64-page analysis accompanying its letter, the state agencies estimate removing trees from California's 1,600 miles of levees would cost $7.5 billion. A variance would save $1 billion.
Either expenditure far exceeds the $5 billion in bonds approved by California voters for flood control projects in 2006.
Levee experts and environmentalists alike said they are disappointed the federal government has shown little flexibility, despite earlier assurances.
California long has operated under a different policy than the rest of the nation, with Army Corps consent. The allowance for mature trees reflected the unique history of flood protection in the state, which left levees as virtually the only remaining riverside wildlife habitat.
After Hurricane Katrina in New Orleans, however, the Army Corps began imposing its national levee maintenance rules on all U.S. flood management agencies.
The move prompted a backlash in California, and federal officials offered a conciliatory response.
In 2007, the Army Corps commander, Lt. Gen. Robert Van Antwerp, stood on a levee in Sacramento's Pocket neighborhood and promised a flexible policy that would preserve trees and habitat.
But the result, a "variance process" recently published in the Federal Register, has caused widespread alarm.
Army Corps officials say the variance lives up to Van Antwerp's promise by striking a balance between habitat and safety.
Rabbon said the policy itself does not require that any trees be cut down. It does, however, establish criteria for maintaining levees, and those criteria require the levees to have nothing other than grass on them, unless a variance is obtained.
The Sacramento Area Flood Control Agency is believed to be the first to seek a variance in California, related to repairs on 30 miles of levees in the city's Natomas basin. Its application, submitted to the corps April 2, cost an estimated $300,000.
Removing trees, if necessary, would cost much more. Once a tree is cut down, the roots have to come out. Otherwise, the dying roots could create a path for water to seep through the levee as they decay. Then the levee must be rebuilt where the roots were.
The corps has agreed to honor California's current arrangement until 2012, when the Central Valley Flood Protection Board will submit a comprehensive regional flood protection plan.