A deep-dive investigation into the causes of last summer’s flooding in New Orleans served to highlight two basic needs — to pursue drainage strategies that go beyond just pumping stormwater out of the city and also to improve communications and cooperation between the Sewerage & Water Board and the rest of city government, Mayor LaToya Cantrell’s chief infrastructure official said Tuesday.

A draft copy of the “root cause analysis,” a 320-plus-page report on the factors that led to severe flooding in several neighborhoods on July 22 and Aug. 5 last year, points to the difficulty of dealing with storms given the city’s aging infrastructure and to institutional failures that compounded the issue.

Those problems are prime challenges for the Cantrell administration, Deputy Chief Administrative Officer Ramsey Green said, even if there are no easy solutions.

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“We are being more transparent as government with this problem, and it is not a small problem,” Green said. “People in this city need to know they have a government that recognizes everything in this report.”

He said the solutions will involve more aggressively embracing the Urban Water Plan, a proposal that calls for storing more water so as not to overwhelm the pumping system during a storm, and creating better communications both among the agencies responsible for drainage and with the general public, Green said.

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The report, obtained Monday through a public records request by The New Orleans Advocate, was put together by ABS Group of Houston, which was paid about $400,000 for the work.

Much of the report covers ground already well-trodden in the year since the August flood brought to the forefront the serious deficiencies in the city’s drainage system. The floods also revealed that top S&WB officials had offered reassurances that everything was fine despite knowing of the system’s failings.

The report charges that a lack of official oversight, knowledge or urgency about the problems with the city’s drainage system allowed it to continue deteriorating, even as it argues that neighborhoods would still have flooded last summer even if the system had been operating at peak efficiency.

The report was commissioned after the Aug. 5 flood by former Mayor Mitch Landrieu’s administration.

Ryan Berni, who was one of Landrieu’s top advisers, said Tuesday that more could have been done if S&WB officials had been candid with the administration about the state of the system.

“I think you saw in the last year us really run into the fire fixing the problem that we were learning more about,” Berni said. “Clearly there had been a culture of misinformation at the Sewerage & Water Board both in its dealing with the public and with City Hall.”

The immediate breakdowns with the drainage system were largely addressed by Landrieu before he left office in May, with $82 million being spent to fix pumps and turbines and to further shore up the system with back-up generators and other equipment. That was aimed at preventing a recurrence of the problems on Aug. 5, when several broken pumps were out of service and not enough power was available to turn on others.

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But the bigger question of drainage in New Orleans can’t rely only on upgraded equipment, Green said.

“For citizens to be confident that the city would be safe in a high rate of rain event … we as a city need to look at what alternatives to catch basins and pumps are, and that’s what the Urban Water Plan is,” Green said.

Key projects in that plan are aimed at storing water in higher areas of the city, so that it does not flow down and exacerbate flooding in lower-lying areas or flood into streets when it overwhelms the pipes and pumps, Green said. For example, a $45 million project underway Uptown is adding water storage under parks.

Breakdowns in communications and priorities caused by the current division of drainage responsibilities between the S&WB — which handles the pumps, power supply and large pipes and canals — and the Department of Public Works, tasked with handling smaller pipes and catch basins, are a consistent theme in the ABS Group report.

The city is now working to better integrate the two agencies, something that was also tried by Landrieu’s administration by placing both under Deputy Mayor Cedric Grant.

Green pointed to what he said were improvements including better information sharing and coordination over projects under Cantrell’s administration, though he acknowledged that overcoming all the potential problems is still a work in progress.

Asked whether the report pointed to the need to put all the city’s drainage under one agency, Green said, “All options are on the table.”

Green also pointed to efforts to improve communications with the public, including more frequent public updates on the status of S&WB equipment and alerts from the administration and the S&WB when heavy rain is expected.

One of the report’s findings was that the city’s Office of Homeland Security and Emergency Preparedness had been barred from alerting residents about approaching serious storms without approval from top city officials, potentially preventing residents from taking steps to protect their property.

“This is a giant opportunity for the city to look at its operations and say, ‘We need to do better,’ ” Green said.

Follow Jeff Adelson on Twitter, @jadelson.​