Hurricane Ida made landfall in Louisiana on August 29, 2021: sixteen years to the day after Hurricane Katrina struck the state. 150 mph winds tore roofs from homes, and roads flooded as some regions received over 13 inches of rain. The storm’s rapid intensification made evacuating New Orleans’ 390,000 residents impossible, leaving everyone wondering: Will the levees hold?
Ida produced storm surges powerful enough to reverse the flow of the Mississippi River, but the levees held.
Since Katrina, the U.S. Army Corps of Engineers (USACE), an engineering branch within the U.S. army, created a flood protection system that could stand up to storms like Ida. Corps engineers went above and beyond with their designs, going as far as to bend the rules to secure the resources they needed. Let’s see how U.S. civil engineers are protecting the people of New Orleans.
Remembering Hurricane Katrina
Katrina originally measured as a Category 5 storm while churning in the Gulf of Mexico, but it weakened before hitting Louisiana as a Category 3 hurricane on August 29, 2005. The storm brought intense wind and rain but came ashore east of New Orleans, leaving many to believe that the city had “dodged a bullet.” The fallacy of that hopeful notion became rapidly apparent.
A storm surge over 25 feet high overwhelmed the levee system, and by August 30, 80% of New Orleans was underwater. Unable or unwilling to evacuate, tens of thousands of residents were left stranded in the flooded city. Many scrambled to their attics or rooftops to escape the floodwaters and await rescue. Over 1,800 people in Louisiana lost their lives. Millions were left homeless in New Orleans, and 400,000 residents left their homes, many never to return to the city.
Surrounded on All Sides
Lake Pontchartrain to the north, the Mississippi River to the south, and swamps and marshes all around: New Orleans is surrounded by water and is five feet below sea level on average. These conditions create a “bowl effect.” When the levee system failed, there was nowhere else for the water to go except into the city of New Orleans.
A Manufactured Disaster
Katrina was as much a manufactured disaster as it was a natural one. After Hurricane Betsy in 1965, the Army Corps began overhauling the region’s flood protection system, but due to budget cuts, the project was only partially completed by the time Katrina hit. Multiple parties share blame for the catastrophe, but in 2006, the Army Corps acknowledged that outdated engineering practices contributed to the system failing,
Protecting Against a 100-Year Storm
After Katrina, congress authorized the Army Corps to design a new flood protection system to defend the Greater New Orleans area against a 100-year storm: an event so extreme that there is a 1% chance of it occurring in any given year.
Bending the Rules
Surveying the damage, Corps engineers realized that protecting against a 100-year storm wasn’t going to cut it. Within decades, the probability of such a storm hitting would dramatically increase, rendering any flood protection system powerless to protect New Orleans — not to mention the fact that climate change is making extreme weather events, including hurricanes, more frequent and intense.
Corps engineers were, shall we say, prudent when designing the new flood protection system. “I never asked them how they got their numbers, and I knew they were higher than what were legitimate,” said then USACE Senior Technologist Don Resio. “I don’t think anybody said, ‘Hey let’s absolutely violate the [100-year rule].’”
Completed in 2018, the Hurricane Storm Damage Risk Reduction System (HSDRRS) is one of the largest and most technologically advanced flood protection systems in the world. The $1.3 billion, 1.8-mile-long Lake Borgne Surge Barrier alone is the largest civil-works construction project ever undertaken by the USACE. This “Great Wall of Louisiana” is part of a system of floodgates, floodwalls and levees designed to protect over one million residents in the Greater New Orleans area, but how would it hold up against another 100-year storm?
Facing a Worst-Case Scenario
The answer came in 2021 with Hurricane Ida. Striking the state on the same day and with stronger winds than Katrina, Ida presented Louisiana with a worst-case scenario. A million people lost power (and the shingles from their roofs), but the system held against one of the most destructive storms in U.S. history. Had the Army Corps stuck to the standards needed to protect against a 100-year storm, it would have failed.
As sea levels rise and the levees settle into the soft Louisiana soil, more work will be needed to reinforce the levees, but for now, New Orleans is protected.
All in a Day’s Work for an Engineer
Corps engineers are essential for protecting our nation from storms and hurricanes, but you don’t have to be a member of the military to make a difference as an engineer.
Mechanical engineers work to make the world a better (and safer) place with every product they design and every system they optimize, and those who aspire to become industry leaders will have the greatest impact.
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Sources:
https://www.britannica.com/event/Hurricane-Katrina/Aftermath
https://www.cnn.com/2021/08/30/us/hurricane-ida-katrina-new-orleans/index.html
https://www.pbs.org/newshour/nation/explainer-ida-similar-to-katrina-but-stronger-smaller
