A few weeks after Hurricane Katrina flooded New Orleans in 2005, I flew over the city in a military helicopter with top brass from the U.S. Army Corps of Engineers.

Seen from the air, the destruction was overwhelming. Massive fishing trawlers had been tossed atop highways. Levees were punctured across the city.

At the time, I remember feeling some sympathy for the Corps, which was being widely blamed for causing a "man-made disaster" that had drowned and killed hundreds of people.

No doubt, the Corps bore some responsibility. But given the scope of Katrina's fury and storm surge, it's hard to imagine what kind of defenses could have saved this city from inundation.

Six years later, I no longer have many soft feelings for the Corps. Its leaders haven't earned it. The post-Katrina era was their moment to engage in some introspection, adapt to a new world and create new partners. Instead of doing so, the Corps has only retrenched, doing whatever it can to deflect responsibility and cover its backside.

There is no better example of this than the Corps' post-Katrina enforcement of its "vegetation management standards." All across the country, from the Sacramento Valley to Seattle and St. Louis, the Corps is effectively telling flood agencies that they need to strip trees on or near levees, regardless of whether they pose a demonstrable threat to flood control.

Never mind that, in California and other states, the Corps and other federal agencies previously spent taxpayer money planting trees along river corridors to benefit wildlife. Never mind that it could cost local agencies billions of dollars – an estimated $7.5 billion in California alone – to clear the trees the Corps now says are a threat to public safety.

Corps officials defend the policy, claiming they are trying to balance the needs of flood control with resource management. They rightly note that a tree next to a levee can gouge a big hole in the levee when it is toppled during a storm.

This is undoubtedly true. Yet the Corps policy doesn't take a selective approach toward figuring out which vegetation poses a threat and which doesn't. It doesn't account for variations in river basins, or whether the levees in question sit in a hurricane zone, subject to huge wind gusts. It doesn't consider whether a levee protects a highly developed urban area or properties of much less value.

"It is just a wrong-headed rule," says Jeffrey Mount, a geology professor and flood control expert at University of California, Davis. "Why would you have a one-size-fits-all policy for a nation that is as large and variable as the United States of America? Why have the same standards for the Mississippi as you have in California?"

Corps officials say their policy is less rigid than critics claim. Flood control districts, they note, can seek a variance to the rules under "a limited range of conditions." While that is true, such a variance can cost big money, as the Sacramento Area Flood Control Agency learned in obtaining one for its levee work in Natomas. SAFCA officials say the variance was one reason project costs in Natomas have risen from $414 million to at least $780 million in four years.

Possibly the most disingenuous claim by the Corps involves its motivation for the policy. Corps officials say the vegetation rules have been in place for decades, and aren't related to the criticism they received following Katrina. Yet if that is the case, why didn't the Corps enforce its policy aggressively prior to Katrina? Could it be that, faced with accusations of gross incompetence following the New Orleans flooding, it decided to rigidly enforce every rule on the books, regardless of merit?

"It's a cover-your-ass mentality," said Mount. "It gets to a culture of engineering where you set these rigid standards, regardless of risk or any other consideration."

Two weeks ago, I railed against the rampant litigation that tends to ensnare nearly all water issues in California.

Yet sometimes, intransigent bureaucracies such as the Corps leave litigants with little choice.

That's why Friends of the River and two other environmental groups filed suit last week in federal court in Sacramento against the Corps' policy. A lawyer for the plaintiffs said the Corps' vegetation rules, if fully enforced, could result in "the most massive intentional infliction of environmental damage on our rivers that we've seen in modern times."

And the damage won't be limited to rivers. If the Corps doesn't rethink this policy, its reputation will suffer further. Allies will forget that the Corps has built some vital infrastructure for the nation and recently made some tough and courageous decisions in managing floods on the Mississippi River.

By clinging to rules such as the vegetation policy, the Corps risks alienating friends in Congress and many of its historic partners. In an era of downsizing government and getting rid of red tape, it is making itself out to be a big, fat target.

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