Daily archives "March 17, 2017"

A look into the levee failures of Huriccane Katrina

Dr Nelson standing along a T-wall levee

Today we explored the 5 myths of levee failure in New Orleans when Hurricane Katrina made landfall, and how the disasters unfolded. Dr. Steve Nelson a Professor at Tulane University guided us through three different levee sites in the lower 9th Ward and talked about how the levees failed during Katrina.

We started off by discussing 5 common myths most people have concerning levee failure in New Orleans.

1. Hurricane Katrina hit New Orleans on August 25th 2005, and left the city mostly unharmed because the extent of the damage occurred after the storm passed. The levees only breached once the storm was gone.
2. The levees ONLY along the Mississippi River breached
3. The “corrupt” Levee Board had built the failed levees
4. Hurricane Katrina was so large that it overwhelmed the city
5. New Orleans is well below sea level.

Dr. Nelson debunked these myths, clearly explaining how things actually went down. The reality of things goes like this:

1. All levees failed during Hurricane Katrina, around 3 hours after it had passed through. ~ 9:00am
2. Hundreds of other levees had breached, most being poorly constructed after the storm of Hurricane Betsy
3. The U.S Army Corp of Engineers built all of the levees as a part of the Flood Protection Act of 1965
4. Hurricane Katrina only really overwhelmed the Gulf Coast. It was a category 5 starting and had died down to a Category 3 once reaching the city. The most devastating part was the levee failures.
5. Only half of New Orleans is below sea level due to how it was built (from draining the swamps and sinking the land).

To get a closer look of the history of the city’s levees, we need to explore the major events that happened pre-Katrina. We’ll begin with the construction of the Industrial Canal. This canal was built in the 1920’s to connect the Mississippi River to Lake Ponchatrain for port access. In the 1960’s, the Mississippi Gulf Outlet was constructed for ship traffic but the U.S Army Corp of Engineers. Both of these canals were major disaster channels during Hurricane Betsy in 1965. The Industrial Canal allowed for storm surge to pass into the city, thus flooding the canals. This in turn heavily flooded the lower 9th ward.

Shortly after Betsy, the 1965 Flood Protection Act was passed by congress in order to ensure protection from future storms and hydrological events. The U.S Army Corp of Engineers carried on the construction of the levees surrounding major canals and drainage channels in New Orleans. The first design of all major levees was the I-wall design. It looked something like this!

View of the industrial canal

Dr. Anderson talked about the “coastal squeeze” and how we need to find as far as the wetland can go and also how far the community can go. The water isn’t allowed to spread inland as it did evolutionary. In 2006 after Katrina hit they rebuilt the entire flood wall and replaced the section on Jourdan St. with a T-wall. There is a big difference in elevation between the Jourdan St. wall and the I-wall in that the I-wall it is 2.5 ft lower and the storm surge took it out because it was not reinforced like the T-wall. Also the flood wall is behind and hasn’t been rebuilt since Katrina. The only reason why they rebuilt the wall on Jourdan St. is because it failed but it seems silly to rebuild the wall to 15ft and leave all the other walls at their original elevation because it provides a pathway for the storm surge to come in.The Army Corps of Engineers admitted in 1985 that they’ve been using the wrong datum (2.5ft too low. 12ft instead of 15ft). The Army Corps of Engineers came up with a new plan to keep the water out of the Industrial Canal entirely because it is connected to Lake Pontchartrain. In the New Hurricane Protection system they built a flood gate on Lake Pontchartrain that keeps the water from entering in from the Lake. There are two gates on the wall. One to allow fruit boats to get out to the Gulf of Mexico through Bayou Bienvenue and another set of gates to allow boats to get to the inter coastal waterway. The wall is 25 ft. high, it’s supposed to keep storm surge out and protect NOLA from the 100 year storm which is a storm that has a 1% chance of occurring every year.

Saving money, but also cutting corners isn’t worth it in the end especially when an entire state is in danger and people’s lives are at risk. Levee failure should not be happening in an ideal world, but hopefully the Army Corps of Engineers learned their lesson.

To learn more, check out these videos