NEW ORLEANS (AP) — More than six years after Hurricane Katrina’s rampage, authorities have taken only halting steps toward identifying weaknesses in a nationwide patchwork of levees intended to protect millions of Americans’ lives and property during potentially catastrophic floods.

The U.S. Army Corps of Engineers, accused of building substandard levees and floodwalls that failed when Katrina swamped the Gulf Coast in 2005, has spent $56 million since then developing the initial phase of a national levee inventory as required by Congress. The Corps on Thursday was releasing a database with information about nearly 14,000 miles of levees under its jurisdiction.

But the inventory doesn’t include what is believed to be more than 100,000 additional miles of levees not covered by the Corps’ safety program. Some are little more than mounds of earth piled up more than a century ago to protect farm fields. Others extend for miles and are made of concrete and steel, with sophisticated pump and drainage systems. They shield homes, businesses and infrastructure such as highways and power plants.

The National Committee on Levee Safety, established after the Katrina disaster to evaluate the system and recommend improvements, issued a report in 2009 calling for the Corps to catalog and inspect every levee so deficiencies could be fixed. But Corps officials say Congress has not provided enough authority or money to add non-federal levees to the database, a massive undertaking that would take years.

“The reality is, we don’t know how many levees are out there,” said Eric Halpin, the Army Corps’ special assistant for dam and levee safety and vice chairman of the levee safety committee. He acknowledged the inventory presently includes only about 10 percent of the likely total.

“I think we’ve done a great job putting forward a state-of-the-art tool,” Halpin said. “It’s a first step. It will be much more powerful once we can get all the data in there.”

For each levee system, the database will include its location, design and rating following one or more safety inspections.

Inspection ratings from nearly 700 of the roughly 2,000 levee systems under the Corps’ jurisdiction have been added to the database thus far, said spokesman Pete Pierce.

Of those, 77 percent had ratings of “minimally acceptable,” meaning they have “minor deficiencies” that make the levees less reliable but are not expected to seriously impair their performance. An additional 11.6 percent were rated “unacceptable,” or likely to fail during a flood, while 11.3 percent were graded as “acceptable,” or without deficiencies.

Experts say the government is moving too slowly to complete the inventory.

“We need to be really candid with the American people,” said Sam Riley Medlock, policy counsel for the Association of State Floodplain Managers and a member of the levee safety panel. “This is yet another class of infrastructure that is aging and posing risks and we’re going to have to do something about it.”

Gerald Galloway, a former Army Corps district engineer and University of Maryland engineering professor, told a Senate committee this month the levee network has “significant” problems and received an overall grade of “D minus” from the American Society of Civil Engineers in 2009. The group estimated that $50 billion worth of improvements was needed over five years.

“So today hundreds of levees, whose integrity is in question, are in place in front of communities and properties with little realistic hope of funding for inspection, repair or upgrade,” Galloway said.

Concern about the levees dates to the 1920s and 1930s, when killer floods on the Ohio and Mississippi rivers led Congress to order construction of more levees. Many were designed for the biggest flood likely to strike a particular area within 500 years or even 1,000 years.

But starting in the late 1960s, federal policies have inadvertently encouraged the building of levees according to a less protective standard, the safety committee report said. One required financially strapped local governments to help cover levee building and maintenance costs.

Relatively low death tolls from major floods in recent decades also fed complacency that ended with Hurricanes Katrina and Rita, the report said. Together, they killed more than 1,800 people and caused $200 billion in damages, spurring calls for a nationwide levee inventory and upgrades.

The portion of the inventory developed thus far includes data on about 13,500 of the 14,700 miles of levees covered by the Army Corps’ safety program. Data on the rest will be added by the end of the year, officials said. Many of the levees are operated and maintained by the Corps, or were built by the Corps and turned over to local officials.

John Paul Woodley Jr., who served as assistant secretary of the Army for public works during the George W. Bush administration, said the Corps has made good progress on the levee inventory but acknowledged “we’re definitely behind where everybody had hoped we’d be.”

Copyright 2011 The Associated Press.