Flood safety by root and branch

The Army Corps of Engineers is on a mission to chop down every tree in the country that grows within 15 feet of a levee -- including oaks and sycamores in Louisiana, willows in Oklahoma and cottonwoods in California.

The corps is concerned that the trees’ roots could undermine barriers meant to protect low-lying communities from catastrophic floods like the ones caused by Hurricane Katrina.

An Associated Press survey of levee projects nationwide shows that the agency wants to eliminate all trees along more than 100,000 miles of levees. But environmentalists and some civil engineers insist that the trees pose little or no risk and actually help stabilize levee soil.

Thousands of trees have been felled already, though corps officials did not have a precise number of how many will be cut.

The corps has “this body of decades of experience that says you shouldn’t have trees on your levees,” said Eric Halpin, the agency’s special assistant for dam and levee safety.

The saws are buzzing despite the outcry from people who say the trees are an essential part of fragile river and wetland ecosystems.

“The literature on the presence of vegetation indicates that it may actually strengthen a levee,” said Andrew Levesque, senior engineer for King County, Wash., where the corps wants trees removed on the six rivers considered vital to salmon populations.

The anti-tree policy arose from criticism directed at the corps after Katrina breached levees in New Orleans in 2005. The agency promised to get tough on levee managers and improve flood protection.

In 2006, the corps began sending hundreds of letters to levee districts across the nation, ordering them to cut down “unwanted woody vegetation,” a prospect that could cost many of the districts millions of dollars each in timber-clearing expenses.

Inspectors began an inventory of the levee system and told districts to fill in animal burrows, repair culverts and patch up erosion.

If they fail to comply, the agencies risk higher flood insurance premiums and a loss of federal funding.

“The corps’ new edict was regarded as a major change in policy,” said Ronald Stork, senior policy advocate with Friends of the River in Sacramento. “Something that is cheap and inexpensive is a chain saw. It was something to do that didn’t cost a lot of money that made you feel better.”

Last summer, the cutting crews came to Columbia, La., on the wooded Ouachita River levee at Breston Plantation, an 18th century French colonial estate.

The plantation is surrounded by sycamores, live oaks, elms, pines, cedars, magnolias and crepe myrtles. Hundreds of trees grow within 15 feet of the levee. In theory, they would all have to go.

But after months of negotiations with landowners and the Tensas Basin Levee District, the corps agreed to let the district chop down only a few dozen trees on the levee.

“We don’t know how long the trees have been here, but they’ve never caused any problem up until now,” said Hugh Youngblood, 61, whose ancestors came to Breston in the 1800s.

On a recent afternoon, his son, who is named Breston, was upset as he walked the levee, pointing to a heap of limbs.

“They didn’t even find a buyer for the wood or the pulp,” the son said.

In 2007, the corps sought to clear oaks, cottonwoods, willows and other vegetation from 1,600 miles of levees in California’s Central Valley. But state wildlife officials complained that the policy would destroy habitat, and residents in Sacramento and elsewhere objected that it would have turned rivers into little more than barren culverts.

The corps eventually dropped the idea.

In a neighborhood north of Sacramento, the corps plans to rebuild the levees surrounding a basin that is home to 70,000 people and has determined that 900 trees, mostly native valley oaks, must be cut down.

Experts outside the corps say a tree has never caused a U.S. levee failure.

“If trees are a problem, why aren’t we having problems with them?” said George Sills, who formerly worked for the corps’ Engineer Research and Development Center in Vicksburg, Miss. “There’s never been a documented problem with a tree.”

In a March 2008 e-mail, Sills told the corps to remove his name from an updated vegetation policy paper he worked on for the corps. He said he ran analyses for the corps “that looked at the possibility that the trees caused any of the [levee] failures in New Orleans” and “it was determined that trees did not lead to any of these failures.”

Corps officials see it differently.

Halpin, the corps’ dam and levee expert, said the agency does not know whether a tree has ever directly caused a levee failure. But he noted that dam failures have been linked to trees, including a 1970s collapse in Georgia that claimed 39 lives.

The corps also wants to get rid of trees for safety reasons. A treeless levee is easier to inspect and repair during a flood.

But none of that washes with local authorities whose levees are being targeted.

“This is something they’ve dreamed up. It’s like they’re hell-bent to write up some negative reports,” said Frank Keith, levee commissioner of the Tulsa County Drainage District in Oklahoma, where levees contain the Arkansas River. The district is working with landowners to cut trees and fix other problems the corps found with its levees.

The carping frustrates Larry Larson, executive director of the Assn. of State Floodplain Managers, a group based in Madison, Wis., that represents interests such as insurers and engineers.

“If you’re going to have a levee, you have to be able to maintain a levee and make it safe,” Larson said.

Others are skeptical.

In Portland, Ore., residents of the Bridgeton neighborhood on the Columbia River lost a legal fight in 2007 to retain cottonwoods and poplars. About 90 trees were cut down at a cost of $268,000, though the corps planted 255 others nearby.

“They don’t care if that’s good science,” resident Walter Valenta said. “It is their policy.”