The U.S. Army Corps of Engineers is facing stiff opposition to its directive to cut down trees within 15 feet of thousands of miles of levees nationwide.

The corps said trees can harm the structural integrity of the infrastructure, obscure visibility and impede access for maintenance and inspection, hindering flood control operations.

"Proper operation and maintenance of levee systems is a critical component of public safety and the consequences of issues such as vegetation on levees, floodwalls or dams go beyond a breach or failure," said Army Corps of Engineers spokesman Walter Pierce in an e-mail.

But opponents said a tree has never been responsible for the breach of a levee and removing vegetation around levees is an unnecessary cost that harms the environment.

The trees are an essential part of the river system, critics say. "Water, as it's going from the mountains to the oceans, goes under the ground, under the levees, into the floodplain, and as it does it is filtered," said Bob Freitag, director of the University of Washington's Institute for Hazards Mitigation. He said that's the process that provides clean water to the nation’s lakes and rivers, and without the vegetation the process is gone.

The corps promised to get tough on levee managers and improve flood protection after it was heavily criticized for the levee breaches in New Orleans after Hurricane Katrina in 2005. The next year the corps began sending out letters to levee districts ordering them to cut down trees.

In a June 2009 story, the Associated Press said it had done a survey of levee projects around the country and found that the corps had ordered tree removal on 100,000 miles of levees.

Pierce called the article inaccurate and said the corps has "specific authorities for approximately 14,000 miles of levees nationwide. That leaves a large universe of other private and non-corps levees that have not been inventoried or inspected," he said. "It is unknown how big [the inventory] is, where the levees are located, their condition or the consequences of failure."

Freitag said a better solution is tiered levees, moving the levees back or removing them altogether. "If you move the levees back, you have room for plants. The plants slow the river down so there's less velocity."

That keeps the water in the upper reaches longer, reducing the chance of flood in the lower reaches, Freitag said. "By not having the vegetation they lose the filtering, they lose sediment control, the water becomes dirtier, they increase velocity, which means they have to increase armoring so it's kind of a chain reaction."
 

[Photo courtesy of Patsy Lynch/FEMA.]