The Mind-Blowing Flaw That Flooded New Orleans

What happened in New Orleans in August 2005  wasn’t a natural disaster. Don’t get me wrong; Hurricane Katrina was a big storm. By many  measures it was one of the strongest hurricanes to ever crash into a United States coastline.  It’s in the top 10 for largest diameter,

lowest central pressure, highest integrated  kinetic energy and more. Storm surge along parts of the Gulf Coast crested at nearly 28  feet or 8.5 meters, the highest in US history.

There really are no words to describe  the devastation Katrina caused, particularly in New Orleans and the  surrounding areas. Roughly four-fifths of the city was flooded. In some areas the  water rose above the rooflines of houses.

The storm shredded the fabric of the city,  and to this day, more than 20 years later, the population of New Orleans has not  recovered to its pre-Katrina level.

If this were just a story about a major  storm overwhelming the flood defenses, it wouldn’t undercut the tragedy, but  it would be understandable. I think we generally recognize that these kinds of systems  don’t offer absolute protection. The levees and

floodwalls around New Orleans were a sprawling  collection of structures built over many decades. It wouldn’t be out of question for a  storm of the century to simply exceed what those protections were designed to  handle. But that’s not what happened.

There were about 50 individual locations  where levees or floodwalls were breached during Hurricane Katrina. Many of those were  situations where the structure was overtopped by storm surge. But out of those fifty, only three  of those breaches accounted for the majority of

the flows that submerged the heart of New Orleans  and led to nearly half of the disaster’s total fatalities and economic damage. All three of  those breaches happened at surge levels below what the floodwalls were designed to manage. And  I built a model in the garage to show you why.

This video is based on a chapter from  my new Book, Disasters By Design, which you can pre-order right now  at the links below. The book is all about engineering disasters through  history and what we learned from them, and I really hope you’ll consider picking up a  copy. I’ll tell you more about it at the end,

but first, I want to show you this model.  I’m Grady, and this is Practical Engineering.

The land we call New Orleans has a history  stretching way beyond its 1718 founding or the birth of the United States. Originally  inhabited by tribes like the Chitimacha, this area has always been a complex  intersection of human settlement and

flooding. It is strategically located on the  Gulf Coast at the mouth of the Mississippi, the largest river in North America. But that  prime location also comes with challenges, namely that the city’s exposure to tropical  storms is extreme, and, being a river delta,