Long before the levees failed, Sandy Sekmistrz sensed the havoc of Hurricane Katrina from two time zones away. So as the megastorm bore down on New Orleans, she called her father, Michael Neely, and begged him to leave his Lakeview home.

“This looks like the big one, and you need to get out of there,” she warned her father from San Diego, where she had just moved after getting married. “If you die, I’m going to be so mad at you.”

Like so many New Orleans natives, Neely, 52, considered himself a veteran of hurricanes, having weathered some of the worst. If things got too bad, he promised his daughter, he’d strap on his life jacket and make his way to his neighbor’s boat.

“He said, ‘I’m going to go ahead and stay and I’ll be fine,’” Sekmistrz recalled recently. “He had been through Betsy and Camille and had been there through every hurricane ever because he worked for the Sewerage & Water Board.”

Sekmistrz’s fears proved painfully prescient. Floodwaters overwhelmed Neely’s neighborhood. A hole in Neely’s roof offered fleeting hope to his relatives that he had survived. But eventually, his body, still clad in his life jacket, turned up near his neighbor’s boat.

For all of the physical devastation it wrought, the most agonizing element of Katrina was its human toll: At least 1,833 deaths — the vast majority of which occurred in Louisiana — have been blamed on the storm and its attendant flooding, making it the deadliest hurricane to strike the United States since 1928.

Though 1,833 deaths seems to be a consensus number of sorts, no comprehensive list of Katrina victims has been published by state or federal authorities in the decade since the disaster, reflecting the often subjective nature — and the legal ramifications — of deeming a death storm-related.

Drownings and traumatic injuries, due in many cases to impact with flood debris, accounted for a significant chunk of Katrina’s carnage. Those deaths are directly attributable to the flooding. One study chalked up 107 of Louisiana’s storm-related deaths to heart disease.

But many casualties defied simple categorization, especially those occurring out of state — or in parishes not directly affected by the catastrophe — that, nevertheless, appeared to be caused by displacement, a lack of medical treatment or other emergency circumstances. Some happened weeks or even months after the floodwaters receded.

In this sense, the storm took on a Chernobyl-like quality — the cascading fallout of Katrina was not clearly defined by time or geography — that complicated efforts to fully quantify the loss of life.

“There are no uniform standards of how you do this and even what you call a victim,” said John Mutter, a professor of environmental sciences at Columbia University, who attempted to measure the disaster’s extended mortality rate.

Beyond the practical limitations, Mutter referred to a collective shame that may have colored attempts to enumerate the dead. Still, the estimates offered by the affected states amount to “biblical numbers,” he said, noting it’s widely believed that the remains of some victims were never recovered.

“It’s ridiculous, and people are embarrassed by it,” Mutter said of the murky death toll. “It says, ‘I wasn’t properly prepared; I didn’t evacuate, and all the government functions that should have prevented such a large number (of fatalities) failed.’ ”

A snapshot of Katrina’s chaos — and the frenzied effort to document the dead — has been preserved in a list of more than 850 victims compiled by the Orleans Parish Coroner’s Office. The spreadsheet entry for victim No. 490 includes a note that the decedent’s date of death must be incorrect because it’s listed as occurring a week after the autopsy. On the same list, another note says the name of victim No. 203 remained “unclear due to handwriting.”

“After Katrina, we experienced what it was like to have a complete breakdown of civilization,” Dr. Jeffrey Rouse, the Orleans Parish coroner, said in a recent interview. “We knew what it was like to not have a jail, to not have a hospital, to not have lights. There were portions of time in which you walked around the French Quarter and all that was on were gas lights and it felt like 1784.”

‘Nothing worse’

The bodies surfaced along damaged roadways and in marooned attics, where dozens of victims succumbed to dehydration and a lack of medical treatment. Some perished in hamstrung hospitals or amid the stress of slow, last-minute evacuations. Others required a painstaking analysis of dental records to be identified — a process that dragged on interminably in the storm’s aftermath.

“There’s nothing worse than somebody’s dying like this,” Dr. Louis Cataldie, the former East Baton Rouge Parish coroner who led the state’s corpse-recovery effort, wrote in his memoirs. “They find their bodies in the toxic sludge, under furniture that floated about and under the drywall ceilings that crashed down on top of them.”

Tim Bayard, a retired New Orleans Police Department captain, said he told officers participating in early rescue efforts to stay focused on the living while keeping track of the locations of the dead. His team reported finding “dead bodies all over the place,” he said, in a city that was 80 percent flooded. Some six dozen bodies were recovered in the Lower 9th Ward alone.

“We were finding policemen’s family members that were dead,” Bayard recalled. “We were finding bodies stuck on trees, hanging on fences, in the rubber piles. Wherever there was water, there were bodies.”

Images of the dead haunt the memories of first responders. Former state Sen. Nick Gautreaux, who served among the so-called “Cajun Navy” fleet of boat rescuers, recalled one corpse that he said appeared to be “melting.”

Gautreaux also remembers an older woman he passed who was with her family on the outskirts of St. Bernard Parish. The group was surrounded by water but claimed to be fine. The rescuers moved on to save scores of others that day but later learned that the woman, who appeared to be using an oxygen tank, had perished.

In cases like hers, Gautreaux said, death was anonymous. “The moral to the story was that this old lady, no one will ever know who she is,” Gautreaux said. “She sacrificed her life.”

Sarah Blenet, a nurse who was stranded at Chalmette Medical Center and later found herself stuck at the St. Bernard Parish jail, said that “for a long time, I woke up in cold sweats crying” over what she had seen during the ordeal.

Surviving Katrina herself wasn’t the hardest part. “My worst experience was waiting on this guy to die in the hallway,” Blenet said. “I needed to take his oxygen tank and go give it to someone else.”

Harrowing force

The plight of Neely, who died near his Lakeview home, was somewhat unusual in that he was just 52, and Katrina disproportionately affected the elderly and disabled — among them the 35 residents of St. Rita’s Nursing Home, who drowned in their beds and wheelchairs in St. Bernard Parish.

But Neely’s death underscored the deceptive velocity of the floodwaters seen in many areas, a force survivors described as harrowing.

“I never knew water could even make such a noise, and I lived by it for years,” said Clara Rita Barthelemy, 70, who rode out the storm inside the roof of her house in the hard-hit village of Verret, in lower St. Bernard. When the waters receded, she said, “it looked like a bomb had gone off.”

There were other unlikely stories of survival, such as that of Gerald Martin, a septuagenarian who lived off little more than water for 16 days in his attic before being rescued. In a wrenching number of cases, however, older residents who refused — or were unable — to evacuate died in their homes.

One victim, Richard Reysack Jr., 81, of Arabi, declined a ride to Baton Rouge, telling his son he had to remain home to cut the grass after the rain from Katrina. “Don’t hurt my pride; don’t take me out of my home,” he told his son, Richard Reysack III.

In keeping with “the old ways,” as then-Jefferson Parish President Aaron Broussard had put it during a pre-storm news conference, the elder Reysack had moved supplies, including an ax, into his attic, in preparation for possible high water. But the storm surge inundated his home, submerging his roof.

The younger Reysack, who had been stranded at work at a nuclear power plant that shut down ahead of the storm, said he felt his father’s passing in his spirit and knew he had not survived as soon as he saw satellite images of the flooding in St. Bernard.

“It’s hard to look back at this time of the year,” he said, adding that he often wonders whether he could have done any more to save his father. “I feel sad at times. Other times, I get angry.”

‘A gargantuan thing’

As shocking as the death toll was, the authorities feared it to be exponentially greater in the immediate aftermath of the flood, as many neighborhoods were inaccessible. Thousands of people remained unaccounted for, with communication, including cellphone and Internet service, crippled. Mayor Ray Nagin famously said on national television that “it wouldn’t be unreasonable to have 10,000 bodies” in New Orleans, and federal authorities ordered 25,000 body bags.

Dr. Frank Minyard, the Orleans Parish coroner at the time, said he been provided a similarly inflated estimate of the body count upon reporting to a makeshift emergency command center in Baton Rouge. “I just felt like turning around and running out, forgetting the whole deal,” Minyard said. “We didn’t know for months what the total of dead bodies was. It was just a gargantuan thing.”

The death toll presented enormous challenges for local and state authorities, who received invaluable assistance from a federal response squad called the Disaster Mortuary Operational Recovery Team. DMORT, as it is known, established a forensic lab and identification center in St. Gabriel, some 70 miles west of New Orleans.

Cataldie, the former Baton Rouge coroner who served as the state’s temporary medical examiner during Katrina, said the authorities initially received 25,000 reports of missing persons, a number that eventually dwindled to just over 100.

He said the disaster squad conducted more than 800 autopsies but, in the end, was unable to identify more than two dozen victims despite forensic efforts to build family trees. “I still think we could have completed that mission,” he said in an interview. “It still haunts me sometimes that we didn’t.”

Sorting out whether to attribute a death to Katrina was obvious in some cases and highly speculative in others: Should suicides be counted, and if so, for how long after the storm? What about the four people fatally shot by New Orleans police as the city erupted into tumult?

“Workers at ground zero at 9/11 who have contracted diseases, illnesses and died years later are still considered victims of the event,” said Mutter, the Columbia University professor. “It’s easy enough to count bodies, but any time you have a displacement of that sort, with sick and elderly people, you get an extended mortality, more than the official number.”

‘Highly uncertain’ number

A National Hurricane Center report put the estimated number of dead at 1,833, including 1,577 in Louisiana, 238 in Mississippi, 14 in Florida and two each in Georgia and Alabama. That has been the generally accepted number, even though the report noted that, especially in Louisiana, “the number of direct fatalities is highly uncertain and the true number will probably not ever be known.”

For its part, the state Department of Health and Hospitals identified 1,464 Katrina-related deaths in Louisiana through Oct. 1, 2005.

On one hand, Cataldie cast a wide net in tallying storm-related victims, including in the count cases such as a displaced toddler who drowned in a bathtub in a Houston hotel room, said Ezra Boyd, a geographer and disaster scientist who founded DisasterMap.net.

At the same time, Boyd said, the state’s “arbitrary” cutoff date excluded an unknown number of storm victims whose remains were recovered after that date. Minyard, the former coroner, noted that local authorities “found people six months (after Katrina) in attics in New Orleans.”

“There are victims from the Lower 9th Ward and other parts of the city who almost certainly died during the storm as a result of the floodwaters whose remains weren’t recovered in time to be counted in the official death toll,” Boyd said in an interview.

Boyd, who authored a dissertation about Katrina deaths, compiled a database of 1,575 Louisiana victims whose deaths “can be linked to circumstances related to the disaster,” including 631 deaths that occurred outside of the area most impacted by the storm. “I tried to be as inclusive as possible,” Boyd said, “because I felt somebody had to document this as thoroughly as possible.”

For Sekmistrz, whose father died in Lakeview, the agony of Katrina was prolonged by having to wait weeks for Neely’s body to be formally identified. She’s grateful her father lived to walk her down the aisle six weeks before the storm, but she misses his phone calls and laughs, which she called “the greatest in the world.”

A few months after Katrina, Sekmistrz learned she was pregnant, and she was heartened to be given an initial due date of Sept. 21 — her father’s birthday.

“There’s 365 days in the year, and he had been on my mind every day,” she said. “To me, that was my sign that everything was going to be OK.”

Staff writer John Simerman contributed to this report. Follow Jim Mustian on Twitter, @JimMustian.