No escape if you’re late: Even small surges will flood sections of I-10 east and west

When it comes to hurricane evacuation, city and state emergency managers have always stressed there is no room for the “better late than never” mentality. Those who wait, they say, may never get out.

Now a team of engineers has assessed the city’s hurricane protection system and come up with hard evidence to back up that claim — a timely warning, what with the June 1 onset of hurricane season just days away.

The team, engaged by the Lake Pontchartrain Basin Foundation, finds that sections of Interstate 10 on the city’s primary eastern and western evacuation routes will flood long before storm surge threatens levees and floodwalls because they are at ground level unprotected by storm barriers.

Chris Guilbeaux, a deputy director of the Governor’s Office of Homeland Security and Emergency Preparedness, said those weak links are well known and have been factored into the state’s timing of evacuation calls — and its insistence in urging residents not to delay.

“We evacuate before a storm, not during one, which is why evacuation plans are set for 50, 40 and 30 hours before tropical storm conditions [winds of 40 mph] are expected at the mouth of the river,” he said.

“We know those areas will flood because that’s just what happened during Hurricane Isaac,” he said.

One section is a 1.7-mile stretch of I-10 that runs between the hurricane protection levees near Irish Bayou and the elevated Twin Spans that cross Lake Pontchartrain just to the east. The highest elevation of this problem area is about 7 feet.

The other section is a 3.8-mile stretch on the north side of LaPlace between elevated sections of I-10. Its highest elevation is 2 to 3 feet.

The surge from even small hurricanes can top those heights as Category 1 Isaac proved in 2012. That slow-moving storm stalled over the area, allowing the surge to build up on the western reaches of the Pontchartrain basin, eventually flooding I-10 and spilling into homes in LaPlace.

Guilbeaux said the state would like to have those exposed sections of I-10 either raised or protected by levees, but lacks the funds. Even then, evacuation orders would still be issued long before a surge would flood them.

“You don’t get a 7 or 8 foot surge with a 40 miles per hour wind, which is when we issue those orders,” he said. “As always, the best way to avoid trouble is to be prepared, and leave when the order goes out.”

The engineering team said providing protection for those sections could help an additional 5,000 vehicles clear the city.

The team was evaluating how the city’s defenses conform to a “systems engineering” approach, which requires that each link in a system work toward the same goal. In this case the goal is reducing the risk of harm to residents from surge. The low-lying section of a major evacuation route failed that test.

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About Bob Marshall

From 2013 to 2017, Bob Marshall covered environmental issues for The Lens, with a special focus on coastal restoration and wetlands. While at The Times-Picayune, his work chronicling the people, stories and issues of Louisiana’s wetlands was recognized with two Pulitzer Prizes and other awards. In 2012 Marshall was a member of the inaugural class inducted into the Loyola University School of Communications Den of Distinction.

  • Chris McLindon

    While the majority of our flood protection budget is going to things like building a bulkhead in Madisonville and designing a diversion project south of Lafitte, we have these gaping holes in the projection of our major population center. Time to refocus.

  • dimdingledon

    We often hear the SLFPA-E talk about multiple lines of defense when it cones to flood proteciton. One of those lines of defense is evacuation. One would think if this were part of your strategies it would be thoroughly reviewed and examined to be sure it is right. Well the SLFPA-E was told about the approach slabs of the twin spans on the south shore being too low years before Hurricane Isaac even hit. This board just didn’t do anyhting about it. Now almost two years since Isaac and still nothing has been done about it. Poor leadership and lots of hot air by these so-called flood experts. Too busy with the secret oil and gas lawsuit to see the flood threat that is literally at the doors of your new system. I guess that is the way they do things in New Orleans.
    Demand accountability from the Corps of Engineers, the SLFPA-E and the CPRA. All were supposed to insure we got a new flood protection system that we were deserving of and one that would protect us. Instead we have another system in name only (ASINO) that fails to protect us against our actual flood threat. And no one has bothered to review any of the storm surge modeling or the subsequent levee designs. So the levees are too low. Our people were fooled into coming back believing the new system would protect us. We have spent billions of dollars on another inadequate system and no one is held accountable?

  • dimdingledon

    Years ago a similar issue came up in Metairie regarding the Causeway. Instead of leaving the roadway in the flood plain, the Corps elevated the Causeway approaches. Commissioner Tom Jackson strongly objected to leaving the roadway in the flood plain. And the Corps redesigned the system to have the roadway elevated. When the low approaches on the twin spans was brough to the attention fo the SLFPA-E why didn’t it get the same consideration? I guess the Corps and the SLFPA-E feels the people in Metairie and Mandeville are more important than the people in New Orleans East and St. Bernard. What other reason can ine give for solving one problem and not the other?

  • dimdingledon

    And don’t say anything about budgets because the elevated Causeway wasn’t in any budget but it got built.

  • nickelndime

    Looks like the solution is always going to be EVACUATE AND DON’T BE LATE or you will get drowned in your car! Billions of dollars wasted. And yes, it would appear that eastern New Orleans and St. Bernard residents, their homes, their families, their animals, their livelihoods, their schools, and their property are worth less than others that the government, et al. decide are worth more.

  • Edward Richards

    The Louisiana coast is subject to forerunner surge because of the semi-enclosed nature of the Gulf of Mexico and the very shallow offshore waters. This means that the storm tide rises as much as 48 hours before the storm hits the coast, often well before those 40 MPH winds. You can have 3 or more feet of storm tide – enough to close these areas – before the track of the storm is certain enough for our last minute emergency plans to kick in. Our state plan is to start evacuation about the time that the evacuation should be finished. They won that bet for 40 years, because you do not know an evacuation has failed until NO floods and you count the bodies.

    They lost it for Katrina, but they have convinced themselves that the levees will never fail so it does not matter that the evacuation plans are unworkable. So as long as the city does not flood, every evacuation is a success. No one cares how late it was called and how few people actually left. Evacuating in adequate time would mean having to evacuate well before the storm track is well characterized, which means more false alarms. Those false alarms cost a lot of money and political capital.

  • wistlo

    An anecdote from Katrina: Our departure in a two-car caravan was delayed for hours as we unsuccessfully attempted to convince a relative to leave with us. We rolled out of Uptown at at 4:30, heading east. I figured US 90 through the Rigolets would have less traffic than I-10. I was right, but hadn’t figured on the deal coming with a “less road” part, too; in places, water was lapping at the edges of the pavement, At Fort Pike, we crossed over raging whitewater flowing into the lake.

    This all happened less than 12 hours after forecasters finally shifted the storm track our way, and 14 hours before gigantic final surge rolled in around sunrise, and just 13 months after the false alarm from Ivan in 2004.

    The public officials who will have to make the call next time have my sympathies.

  • Moses

    This is an epic failure in planning. This is an epic failure of engineering. It really doesn’t matter what the rest of us are doing in the city to mitigate storm surge when we have an extremely short exit window. Assuming EVERYONE is leaving at the same time the evacuation warning is given, would we still have enough time to clear the city – to clear the I of the 10 needle? Quite a few will die trying to do it right.

  • Roy Arrigo

    Long before the Pontchartrain Basin Foundation became aware of this vulnerability, the dip in I-10 just before the twin span was pointed out the the Southeast Louisiana Flood Protection Authority-East years ago by the homeowners who regularly attend the SLFPA-E meetings. It was also raised by former board member & engineer Stradford Goins. Those warnings were dismissed by a board leadership that was not concerned with flood protection or public safety but with controlling where the money went.

  • Roy Arrigo

    SLFPA-E president Tim Doody always talks about evacuation and that the public should take heed and evacuate when told to do so. But it is his board under his leadership that ignored the warnings of homeowners who pointed out this vulnerability at I-10 and the twin span years ago years ago. That deficiency is so obvious that even a housewife, Epsie Hennessey could see that it was too low and warned the board on the record. They dismissed the warnings and did nothing. So much for this board of experts led and controlled by an accountant and a book writer.

  • Steve Murchie

    “Author.” A “book writer” is called an author.

  • nickelndime

    NO ESCAPE: I have no sympathy for public officials. They are overpaid, and I am not getting my money’s worth. I would like a refund please, thank you very much. When I leave this city, it won’t be because Mitchell has issued a warning to do so. As a matter of fact, I do not see any mandated evacuations in the near future, because, to be quite frank, Mitchell doesn’t have the wherewithal to order anything, much less his lunch!