The condition of flood control systems came into dramatic focus in August 2005 when Hurricane Katrina’s rain and storm surge toppled levees in New Orleans and tore up the Gulf Coast. It left 1,800 people dead and was the costliest storm in U.S. history with damage estimated at $108 billion.

Afterward, Congress told the Corps to catalog federally overseen levees, many of which it built and handed over to municipalities to run and maintain. The Corps has spent more than $140 million on inspections and developing the inventory.

As of Jan. 10, the agency had rated 1,451 or 58 percent, of them. Of those, 326 were unacceptable, 1,004 were minimally acceptable with deficiencies that need correcting, and 121 were acceptable.

In the AP’s examination, among the most widespread issues were:

— Design or construction flaws.

Some levees had inadequate “freeboard” — extra height to prevent overflow, which can weaken the landward slope of the levee. For example, the Corps found there was not enough height in a levee along a 20-mile stretch of Mississippi’s Yazoo River system, which came close to being overtopped in 2011 during historic flooding of the Mississippi River valley.

— Inadequate or crumbling infrastructure.

Many pipes built into levees to drain storm water were made of metal that has rusted. And pumping systems are giving out. In Brookport, inspectors found inoperable pumps and deteriorating pipes in its 6-mile-long earthen levee. Their report said a gaping hole just outside town has put the structure in “critical condition.”

— Failure to control vegetation and invasive animals.

Corps specifications require that levee slopes be kept clear of plants and burrowing critters such as ground squirrels and gophers. The tunnels could weaken the walls by providing pathways for water. Thick vegetation also can conceal cracks, holes and unstable slopes. A 2010 Corps report found parts of a 2.2-mile-long Mississippi River levee in South St. Paul, Minn., dotted with trees, brush, weeds and tree stumps.

— Building encroachment.

The Corps requires a 15-foot buffer between levees and man-made structures such as houses, fences and parking lots. But some structures abut levees or rest on top of them.

Part of an 11.5-mile levee built to protect downtown Augusta, Ga., from the Savannah River was incorporated into a park featuring a brick walkway, lighting and landscaping. A townhouse subdivision and access road were built atop the levee, as were sections of a hotel, a church hall and a science museum.

In Toledo, Ohio, some 1,500 homes, patios, stairs and other structures have been placed on the levee that runs along Lake Erie’s Maumee Bay. “You name it, it’s out there,” said Robert Remmers, a Corps levee safety program manager who oversees Toledo’s system.

Local officials say that in many cases the Corps allowed such incursions — or didn’t object to them.

Tom Robertson, a consulting engineer for Augusta, said the Corps signed off on the commercial buildings encroaching on its levee in the 1980s and 1990s, and the Corps knew about the townhouse development and did not formally approve it.

Eric Halpin, Corps special assistant for dam and levee safety, said the agency had sometimes allowed builders to take liberties that wouldn’t be permitted now. The Corps doesn’t expect local officials to tear down neighborhoods or hotels, but has orders from Congress to tell them about levee problems and risks, he said. In many cases, additional walls or other steps can improve safety.

In interviews, some local managers disputed their “unacceptable” ratings, saying their levees were sound, if not perfect.

Bill Sheppard, assistant chief engineer for the Yazoo-Mississippi Delta Levee Board, noted that none of its levees failed during severe flooding in spring of 2011. “Our system works,” he said. “Does it have components that need to be fixed after this flood? Absolutely. But if you look at the levee evaluation reports, you’d think, ‘Oh Lord, run for the hills.’”

A number of local managers blame their “unacceptable” ratings on the Corps taking a harder line on compliance with levee construction, operation and maintenance standards.

“Since Katrina, they’re almost hyper-vigilant,” said John Sachi, city engineer for South St. Paul. “It’s almost like they’re remedying their mistakes from the past by putting the onus on us to make sure things get better.”

Sachi said South St. Paul is spending $2.5 million to replace an outdated pumping station and correct other deficiencies.

The Corps’ Halpin agreed that levees covered by the agency’s safety program mostly held their own during some of the heaviest flooding on record in 2011, which caused an estimated $9 billion in damage. But that doesn’t mean inspectors are overstating the system’s flaws, Halpin said, noting that some communities escaped catastrophe only after heroic efforts to shore up levees more than half a century old.

“That is not acceptable performance,” he said.

A number of local officials said they would happily upgrade their levees — if they could afford it. “There is no money available. There’s no way we could raise even a 25 percent match if they covered the rest of it,” said Askew, Brookport’s mayor.

A concrete floodwall about 10 feet high tops the section nearest the Brookport business district. Askew said the levee proved itself during the 2011 flood, when the town was mostly spared as the river swirled within a couple of feet of the top. The mayor figures the government should pay for about $2 million in upgrades.

After Katrina, California voters approved nearly $5 billion in bonds to shore up the state’s aging flood protection system. With more than half the money spent, officials say they need up to $12 billion more to finish.

In Sacramento, a 42-mile-long levee along the Sacramento and American rivers protects the Natomas area, a flood-prone basin transformed from cropland into a community of 100,000 with an airport, nearly three dozen schools and two interstates. If the levee were to fail, “it would be beyond catastrophic,” said Angelique Ashby, the city’s vice mayor.

The levee’s unacceptable rating led federal emergency officials to impose strict building limits that have prevented homeowners from making repairs and delayed construction of schools and a police station, she said.

About half the $810 million needed for upgrades has been raised from state and local sources, and much work has been done. The city is seeking federal financing of the rest.

In 2009, a congressional advisory panel recommended that Congress invest in levees, create national levee programs and enact policies to increase awareness about the risks of flooding. But Congress has yet to adopt the group’s report. In the meantime, experts are warning that aging and weak flood-control systems will likely face stiffer tests as climate change makes severe storms more common in the coming years.

“This is going to be a national problem and it just hasn’t dawned on people how big it’s going to be,” said Jeffrey Mount, a levee management specialist and founder of the Center for Watershed Sciences at the University of California, Davis. “We’re in a never-ending cycle of flood and rebuild.”

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John Flesher reported from Brookport, Ill., and Traverse City, Mich., and Cain Burdeau reported from New Orleans. AP reporter Troy Thibodeaux contributed from New Orleans and AP video journalist Haven Daley contributed from Sacramento.