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Timeline maps course of post-Katrina deluge

City’s fate sealed in hours

By Bob Marshall
Staff writer

Generations of New Orleanians worked for 300 years to raise a great city in the often inhospitable terrain along the banks of the Mississippi River.

It took Hurricane Katrina less than six hours to put that labor of love under water, damaging 200,000 homes and killing more than 1,200 people.

Timelines developed by forensic engineering teams probing the failure of the hurricane protection system provide a slow-motion picture of a deadly tragedy that unfolded with surprising speed.


The costliest natural disaster in the nation’s history began early Monday, Aug. 29, with a small leak near the Interstate 10 High-Rise about 4:30 a.m. and climaxed with the horrific collapse of floodwalls along the 17th Street and London Avenue canals between 9:30 and 10:30 a.m.

It would take many more hours for the water to reach neighborhoods far removed from the gaping wounds in the city’s defenses, but by the time the last section of the London Avenue floodwall came down, the breadth of the damage was inescapable.

The unprecedented scale of devastation to a modern American city has drawn researchers from around the world hoping to mine lessons from the experience. Understanding the sequences of the failures and the paths of the floodwaters has been a part of that effort. Scientists with the Louisiana State University Hurricane Center and others working with an Army Corps of Engineers investigation have scoured the area for evidence to pinpoint the times of failures. Their sources have included witness accounts, video, photos and data on water levels recorded by instruments at many of the canals.

But researchers say the times listed are mostly best estimates because even the witness accounts include differences. For example, witnesses’ accounts of the 17th Street Canal breach vary by as much as one hour, according to the Interagency Evaluation Task Force, which is doing an investigation for the corps.

Hurricane specialists knew there would be flooding to study as Katrina moved toward southeast Louisiana. Storm-surge models done by LSU showed the area’s eastern defenses of levees and floodwalls would be topped.

But the models predicted the flooding would be far less than catastrophic in most neighborhoods, with water levels staying below 3 feet, because the surge would last for less than two hours.

Breaches in those defenses changed everything. With levees and floodwalls down, water poured into the metro area until the volume in the infamous “New Orleans bowl” — actually a series of bowls bounded by levees and natural barriers — was at the same level as lakes Borgne and Pontchartrain, something that didn’t finally occur until Thursday, Sept. 1, about 2 a.m. The floodwater rose for days instead of hours, and inconvenience had become a deadly tragedy.

Researchers now say as many as 30 breaches in the system accounted for 84 percent of the metro area flooding, with most of the water coming from the big gaps along the 17th Street, London Avenue and Industrial canals, as well as holes in the Mississippi River-Gulf Outlet and Gulf Intracoastal Waterway levees and a gap in the Orleans Avenue outfall canal that flooded much of the City Park area.

Determining the specific source of water that flooded various sections of the city is difficult because several breaches could have affected the same neighborhoods, researchers said. However, a report by LSU marine scientist Paul Kemp made these estimates for the larger sections of the metro area:

St. Bernard Parish: 89 percent of the flooding came through breaches in the MR-GO levees on the eastern side of the parish and from the Industrial Canal, also called the Inner Harbor Navigational Canal, on its northern end.

Eastern New Orleans: 63 percent of the flooding came from breaches along the Gulf Intracoastal Waterway and the Industrial Canal.

The rest of New Orleans: 87 percent came through the holes in the 17th Street, London Avenue and Industrial canals, as well as the gap in the Orleans Avenue outfall canal.

“We have a reasonable measure of which breaches added water to different bowls of the metro area,” said Ivor van Heerden, assistant director of the LSU Hurricane Center and a member of the state team investigating the levee failures. “We’re more confident about the times. We’re confident this started around 4:30 in the morning.”

That first step in the flooding of New Orleans was small, and came at an unexpected spot. The water it released was a small stream rather than a torrent. But investigators have discovered that the circumstances underlying it would become a theme to the shocking systemwide collapse that drowned the region.

Investigators have constructed this timeline for the flooding:

4:30 a.m. or shortly before: Rising water on the Industrial Canal begins leaking into neighborhoods on either side of the I-10 High-Rise at the CSX railroad crossing. Metal gates designed to prevent such leaks had been damaged by a derailment, removed and replaced by sandbags, according to LSU researchers. The flow continues for about 13 hours, with water moving east into neighborhoods off Downman Road and west into the greater metro area, including the Pontchartrain Park, Gentilly and Desire areas. This is relatively minor compared with what those areas would face in just a few hours.

5 a.m.: The storm surge is still well below the top of the levee on the west side of the MR-GO in St. Bernard Parish, but the pounding of 5-foot to 7-foot waves driven by Katrina’s winds and the speed of the storm surge moving up the channel already are having an effect on the poorly built structure. By dawn, sections of the slopes facing Lake Borgne are starting to crumble. Entire sections eventually would disintegrate. Water begins moving into the marsh between the MR-GO and 20-Arpent Canal levee.

6:10 a.m.: Katrina makes landfall at Buras on the west bank of the Mississippi River in Plaquemines Parish. The initial storm surge pushes against the hurricane protection levee on the western edge of the parish but does not overtop it. However, as the storm moves north with a counterclockwise rotation, high winds from the northeast drive a 21-foot surge that rolls over the eastern half of Plaquemines and the river, then over the levees on the west side of the river. Communities between Port Sulphur and Venice that were not destroyed by Katrina’s winds are inundated by a flood that will remain for days.

6:30 a.m.: Witnesses report sections of the floodwall on the east side of the 17th Street Canal are leaning toward Lakeview. There is no breach yet, but water is pouring through the cracks. This is less than a trickle of what would follow.

6:30 a.m.: The storm surges moving up the MR-GO and the Gulf Intracoastal Waterway come together where the two channels meet in eastern New Orleans, the now infamous “funnel.” Squeezed into a narrower single channel constricted by levees, the surge gains speed, power and height. The levees begin yielding, eroding and breaching in numerous spots. The first breaks seem to occur along the “spout” of the funnel west of the junction of the two waterways; others will occur close to the junction, and some on the north side of the Intracoastal Waterway east of the junction. Breaches on the north side send water into homes across eastern New Orleans from the Chef Menteur Highway area to the newer subdivisions along I-10.

6:50 a.m.: The surge from the funnel has reached the Industrial Canal, spilling south toward the river but also rushing north toward Lake Pontchartrain, which at this point is 10 feet lower than the water in the canal. The surging water quickly begins flowing over the floodwalls and levees on both sides of the canal, heading into the Lower 9th Ward, upper St. Bernard Parish, the Upper 9th Ward, Gentilly, Bywater, Treme and even into Broadmoor. The worst is still ahead.

7:30 a.m.: The levees on the west side of the Industrial Canal at the railroad yard between Florida Avenue and North Claiborne Avenue breach, dramatically increasing the flooding in the Upper 9th Ward, Bywater and Treme. This flooding continues for 12 to 15 hours.

7:45 a.m.: The I-wall and levee on the east side of the southern end of the Industrial Canal catastrophically breach in two sections and send a wall of water into the Lower 9th Ward, killing people as houses are flattened and automobiles are tossed around like toys in a bathtub. As it flows south, the water stays high enough to flood homes in Arabi and other neighborhoods in the northern end of St. Bernard Parish.

8:30 a.m.: The milelong stretch of floodwall behind Lakefront Airport that is 2 feet lower than the adjacent earthen levee is overtopped by the surge from the lake. Water pours into eastern New Orleans homes for about three hours.

8:30 a.m.: With large sections of the MR-GO levee gone by 6 a.m., Lake Borgne advances to the 40-Arpent Canal levees. Now it begins moving over the top of this second barrier. Water starts rushing into neighborhoods from Poydras to Paris Road.

9 a.m.: As the storm surge in the London Avenue Canal reaches 10 feet — 4 feet below design capacity — sections of the floodwall on both sides start bending away from the canal, one just south of the Robert E. Lee bridge and another just south of Mirabeau Avenue bridge. Water starts leaking into adjacent yards, but the flow is minor at this point.

9:30 a.m.: The stressed sections of I-wall on the east side of the London Avenue Canal near Mirabeau finally give way, sending a wall of water through homes and adding to the general flooding in Gentilly, including at Dillard University and the University of New Orleans

9:45 a.m.: A catastrophic break at the 17th Street Canal floodwall and levee occurs, releasing a roaring torrent of water into Lakeview that collapses homes and claims lives. The nation would watch in disbelief for the next 60 hours as the corps struggles to plug the gap. This breach accounts for most of the water that destroys homes and ruins lives from the Jefferson Parish line east to City Park, north to the lake and south to the river.

10:30 a.m.: A section of I-wall south of Robert E. Lee Boulevard on the west side of the London Avenue Canal comes down, sending an 8-foot wall of water through homes in Gentilly and contributing to the rising flooding across the city.

This is the last major breach. With Katrina already north of the city and quickly moving away, the surge has begun to drop. For levees and floodwalls still standing, the overtopping is over. But the large sections of levees and floodwalls that have collapsed will keep bleeding water into the city for more than four days.

It would take weeks to get the water out.

http://www.nola.com/newslogs/tpupda...ola_tpupdates/archives/2006_05_13.html#140750
 

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An excellent timeline of what happened. We heard reports of water on Hayne over the levee board radio here at the NWS around 730 AM but no breach reported yet where they were near UNO. Held off on issuing anything for levee breach. However...around 8 AM...got a report of a major breach on the Industrial Canal at the Lower 9. The levee board radio stopped working shortly after that. Issued our FFW around 815 AM for Orleans and St. Bernard for flooding up to 6 feet deep. The rest is history.
 

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To be quite honest, I had heard of around a dozen breaches, which I thought was enough to inundate the City, but, I did not know that there were 30 breaches in the system. But, looking at the aftermath and the height of the strom surge, I can see how this is certainly possible. The Army Corps of Engineers is working full time on this mammoth problem and, now, I can understand why. In this post on another forum, I highlight a conversation I had with some "out of town" workers on our levee system.... http://hornetsreport.com/HRForums/showthread.php?t=33683
 

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What a differnt world it would be if the walls hadn't broken and collapsed. Thanks for posting this. This is the first account I've heard of the situation in Buras, where I lost a camp. The Parish levees on the west side held, just as I had suspected. The federal levees along the river wiped that area out. Makes sense, because debris fields are in that direction. Very interesting article. Thanks. Amd thanks for the news on the 10 year repair. That is EXCELLENT NEWS!!! I often wondered what they were going to do with the area that didn't break that were made in the same way as the ones that did break. This just made my day.
 
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