Field Trip

The Geology of the Hurricane Katrina Disaster in New Orleans—What Happened?

0900–1600, Sunday, 4 October

The bus will depart the Morial Convention Center at 0900 hours and return by 1600 hours. Lunch, beverages, and a handout with supporting illustrations are included in the registration cost. Purchase a ticket to this event.

Hurricane Katrina struck the US Gulf Coast on 29 August 2005. A 20-ft storm surge was experienced in southeast Louisiana, with 18 ft of surge reaching the eastern margins of the greater New Orleans area. Levees failed along several critical canals, which resulted in more than 80% of the city being flooded.

This field trip offers a glimpse into what happened that day, what were the lessons learned, and how is New Orleans recovering.

The first stop on the trip is to the Lower 9th Ward, a residential neighborhood that was destroyed from the Industrial Canal levee breach. The top of the floodwall along this canal was supposed to be at an elevation of 14.5 ft above sea level, but due to an error involving the use of the wrong datum by the US Army Corps of Engineers and to subsidence, the top of the wall was only at an elevation of 12 ft above sea level. In June 2006, this floodwall was replaced with a T-wall at the proper elevation. As we travel down the streets, you can still see the standing water line on the buildings that remained intact.

At the second stop, we will visit the southern side of the London Avenue Canal, as well as several other canals, which have been draining rainwater out of the low lying areas of New Orleans since the mid 1800s. This canal suffered a floodwall breach and has since been replaced with a T-wall. At this stop, we’ll discuss the fatal errors made with this canal and why better plans were never made, such as movable gates or raising the height and width of the levees.

On the northern side of the London Avenue Canal, we’ll visit another section of I-wall, about 450 ft long, that failed. Immediately across from this failure, on the east side, the wall didn’t fail but leaned by about 5o away from the canal. Both have been replaced by T-walls. Moveable temporary flood gates were also built in 2006. At this stop, we’ll walk up onto the levee, and you can see that there is still a problem in the flood protection system—the height of the floodwall drops by 2 ft to the bridge abutment, so there is no protective seal between the wall and the bridge.

The next stop is to Lakeshore Drive near Lake Pontchartrain. The levees along the lakefront were not overtopped by the storm surge. However, to the east of the Industrial Canal, the storm surge did overtop the levees and floodwalls and created an erosion trench at the base of sections of floodwall. Construction of the flood gates might have prevented the storm surge from entering the lake during Katrina and thus could have prevented the flooding due to breaches on the drainage canals. New floodgates and pumps have been built since Katrina.

Our fifth stop will be to the area of a breach on the 17th St. Canal. It occurred along a 500 ft section of the levee. In years prior to Katrina, seepage through the levee was noted by residents along the canal, a clear sign of potential problems, but was never pursued.

The final stop is at the levee of the Orleans Canal just under the I-610 overpass. As we walk up to the levee, you’ll see that the floodwall on the top of the levee abruptly ends about 40 yards north of the overpass, creating a 100-yard gap in the flood protection on the canal. During Katrina, water from the Orleans Canal was flowing freely through this gap as evidenced by the erosion that occurred around the support structures for the freeway overpass. Fresh concrete has since been poured around these structures, and the levee has been raised about 2 feet from its pre-Katrina level in an attempt to fix the problem.

See additional details and photos of pre- and post-Katrina New Orleans.