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In a sweeping new study of the causes of the disaster in New Orleans last year, the Army Corps of Engineers concludes that the levees it built in the city were an incomplete patchwork of protection, containing flaws in design and construction and not built to handle a storm anywhere near the strength of Hurricane Katrina.

"The hurricane protection system in New Orleans and southeast Louisiana was a system in name only," said the draft of the nine-volume report, released yesterday in New Orleans.

Several outside engineering panels that have been critical of the corps have come to similar conclusions, and have found a more extensive chain of flaws in the design, construction and maintenance of the 350-mile levee system.

But the 6,113-page report is remarkable for being a product of the corps' own official investigation, which brought together 150 experts from government, academia and business to study what went wrong and how to build better systems for the future.

The region's network of levees, floodwalls, pumps and gates lacked any built-in resilience that would have allowed the system to remain standing and provide protection even if water flowed over the tops of levees and floodwalls, the report's investigators found. Flaws in the levee design that allowed breaches in the city's drainage canals were not foreseen, and those floodwalls failed even though the storm waters did not rise above the level that the walls were designed to hold.

But the system was also overwhelmed in significant ways by Hurricane Katrina, and some degree of flooding would have happened even if the floodwalls had not been breached by the surging waters, the report stated.

"Regardless of breaching or no breaching, there would have been massive flooding and losses" from the hurricane, Lewis E. Link, the director of the study and a senior research engineer at the University of Maryland, said in an interview. "The losses were increased because of the breaching that occurred."

The investigators found no evidence of negligence or malfeasance by the corps or its contractors, but said the corps had failed to take into account the tendency of the local soil to sink over time, leaving some sections of levee lower than they should have been. The corps did not re-examine the heights of levees even after it had been warned about the degree of subsidence, the report said.

Similarly, the corps designed the system to protect New Orleans against a relatively low-strength hurricane, the report found, and did not respond to warnings over the years from the National Oceanographic and Atmospheric Administration that a stronger hurricane should have been the standard.

The report suggested the corps has had trouble keeping up with the fast-changing world of geotechnical engineering, and does not share critical information among its many parts. Although the corps had indications that the floodwalls might fail under intense storm conditions, "the pieces were not put together to solve the puzzle," the report said. More must be done, it concluded, to share information among those who do research and those who design and build systems.

The report, which is already being used in the repair and improvement of New Orleans's flood protection, warned that the area "remains vulnerable" to any storm with surge and wave conditions like Hurricane Katrina's.

The chief engineer of the corps, Lt. Gen. Carl A. Strock, said in an interview that the report showed that "we missed something in the design," particularly in the construction of the drainage canal floodwalls that caused so much of the flooding.

According to the report, the corps designers did not anticipate the way the floodwalls would fail as water climbed high against them: in several breaches, including the one at the 17th Street Canal, the force of the water pushed the floodwall back slightly, opening a gap deep into the earthen levee below that allowed water to course down under high pressure and push the wall aside.

General Strock did not go so far, however, as to apologize on behalf of the corps for the decades of decisions that went into the system.

"It is what it is," he said. "Call it a mea culpa, or call it a dry recognition, or admission, or whatever — but we're not ducking our accountability and responsibility in this."

Nonetheless, he made it clear that he believed outside influences had played a role in the problems of the flood protection system, though he said that did not absolve the corps. As one example, he cited plans by the corps in the 1970's to put large barriers at the narrow openings between Lake Pontchartrain and the Gulf of Mexico.

The corps backed off from that plan after a court challenge from environmental groups and then proposed floodgates at the city's drainage canals. But local officials of the levee boards and sewerage and water boards blocked that plan, as well. So the corps went with the next fallback plan of building floodwalls in the canals.

"Each time, we backed off," General Strock said. "Each time we did that, we assumed an increment of risk. I don't think anybody looked back and said, 'Risk, risk and risk adds up to unacceptable levels.' "

He said this was not an effort to lay blame at the feet of others, because ultimately the corps had responsibility for what it built.

"At the end of the day, we have to stand by the decisions," he said. If the corps builds floodwalls, he said, those floodwalls have to stand up to the test and the system has offer the intended level of protection. "And we didn't get there," he said.

The corps announced this week that it had substantially met its goal of repairing the city's hurricane protection system by June 1, the beginning of hurricane season, though there was significant work still to be done, including on two of the three enormous gates at the mouths of the city's major drainage canals.

If an unseasonably early hurricane approaches with threats of a storm surge, corps officials say, they will drive sheets of steel across the mouths of the canals and remove the rainwater with portable pumps. That could lead to street flooding, but should prevent the catastrophic breaches that allowed Lake Pontchartrain to pour billions of gallons into the center of the city.

A setback was announced this week as a 400-foot section of levee in Plaquemines Parish, south of New Orleans, shifted as it neared completion. The marshy soil of the area could not support the weight of the earthen levee structure, which slumped and bulged. It is being repaired.

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Robert G. Bea, an engineering expert at the University of California, Berkeley, who has been critical of the corps, said he was impressed by the level of criticism in the report.

"This report has got a tone in it that is not like anything we have seen before," Dr. Bea said. "They're coming forward now."

But he said he wished that the corps had admitted other failures and gone further in delving into the internal reasons for those failures. A report by Dr. Bea and colleagues, released last month, said organizational dysfunctions within the corps had created an environment with little responsibility or accountability, and within which safety concerns could be easily played down.

Yesterday's report did not address that question in depth, but General Strock said it would be dealt with in a subsequent study.