The failure of the levees and the flooding of New Orleans during Hurricane Katrina on August 29, 2005, represent the first time in history that an engineering failure has brought about the destruction or near-destruction of a major U.S. city. The ASCE Hurricane Katrina External Review Panel stated that
“The catastrophic failure of New Orleans’s hurricane protection system represents one of the nation’s worst disasters ever.A storm of Hurricane Katrina’s strength and intensity is expected to cause major flooding and damage. A large proportion of the destruction from Hurricane Katrina was caused not only by the storm itself, however, but also by the storm’s exposure to engineering and engineering-related policy failures” (ASCE Review Panel 2007, p. v).
Hurricane Katrina made landfall in the early morning of August 29, 2005, in southeast Louisiana to the east of New Orleans. Throughout the area, levees and flood walls failed or were breached in more than 50 locations. Eighty percent of the city of New Orleans was flooded, to a depth of more than 3 m (10 ft) in some neighborhoods. The extent of the destruction made it difficult to account for the victims, but the toll a year later was listed as 1,118 dead people and 135 missing and presumed dead. More than 400,000 citizens fled the city, many never to return. Property damage reached tens of billions of dollars (ASCE Review Panel 2007, p. 1).
Wind and storm surge are the damaging agents of a hurricane, storm surge at the coast and the wind away from the coast. Storm surge is a combination of wind-induced water motion, the reduced atmospheric pressure in the storm, and possibly high tide. Hurricane Katrina, unfortunately, came ashore at high tide, and the storm surge in Plaquemines Parish reached as much as 6.1 m (20 ft) above sea level. In Lake Pontchartrain, directly to the north of New Orleans, wind from the north piled water up as high as 3.7 m (12 ft) above sea level. The hurricane also brought heavy rainfall, increasing the probability of flooding (ASCE Review Panel 2007, pp. 13-16).
“The Lake Pontchartrain and Vicinity Hurricane Protection Project system experienced the worst damage during and after Hurricane Katrina and resulted in the most serious consequences to the city and people of New Orleans. The massive, destructive flooding of New Orleans was caused by ruptured at approximately 50 locations in the city’s hurricane protection system. Of the [457 km] 284 miles of federal levees and floodwalls-there are approximately [563 km] 350 miles in total-[272 km] 169 miles were damaged” (ASCE Review Panel 2007, p. 25).
Failures of the system began even before Hurricane Katrina made landfall, with overtopping of the Mississippi River-Gulf Outlet levees and flooding of parts of St. Bernard Parish. Shortly after landfall, at 6:30 a.m., levees on the south side of the New Orleans East neighborhood were also overtopped and breached. Shortly thereafter, waves reached 1.2 m (4 ft) in the Industrial Canal, causing more overtopping and flooding. Four I-walls also breached, between about 5:00 and 8:00 a.m., even before the water rose high enough to overtop them (ASCE Review Panel 2007, pp. 25-27).
With all of the breaches, some neighborhoods flooded to the rooftops in minutes. Even where the flooding was slower, further from the sites of the breaches, the water rose approximately 0.3 m (1 ft) every 10 min. The deadliest breaches were in the Industrial Canal and the London Avenue Canal. These canals extended south from Lake Pontchartrain into the heart of the city, adding to the rapidity of the flooding (ASCE Review Panel 2007, pp. 28-31).
As the hurricane moved north that morning, the storm surge receded, but the damage had been done. Once the I-walls failed, the city continued to flood until the water level was equal to that of Lake Pontchartrain. By September 1, more than 80% of the city was flooded, much of it 2-3 m (6-10 ft) deep. The pump stations were no longer working, and in any case, the water couldn’t be pumped out until the levee breaches were repaired (ASCE Review Panel 2007, pp. 31-32).
The consequences of the failure are discussed in detail by the ASCE Review Panel (2007, pp. 33-46). In essence, the city and its economy were destroyed, and much of the population moved away permanently. A year and a half later, much of the city remained almost uninhabited and uninhabitable. The failures also, understandably, shook the public’s faith in the civil engineering profession.
The hurricane protection system for New Orleans was and remains badly flawed. Moreover, loss of public confidence in the system has seriously hampered the reconstruction of the city. People remain reluctant to move back and invest.
According to the ASCE Review Panel, “we must place the protection of public safety, health, and welfare at the forefront of our nation’s priorities” (ASCE Review Panel 2007, p. 73). The specific recommendations made by the panel, with 10 specific calls to action classified under four recommended changes in thought and approach, were the following:
” Understand risk and embrace safety
o Keep safety at the forefront of public priorities
o Quantify the risks
o Communicate the risks to the public and decide how much risk is acceptable
” Re-evaluate and fix the hurricane protection system
o Rethink the whole system, including land use in New Orleans
o Correct the deficiencies
” Revamp the management of the hurricane protection system
o Put someone in charge
o Improve inter-agency coordination
” Demand engineering quality
o Upgrade engineering design procedures
o Bring in independent experts
o Place safety first (ASCE Review Panel 2007, pp. 73-82).
Some specific deficiencies that need to be corrected, listed under call to action 5, “correct the deficiencies,” were to establish mechanisms to incorporate changing information, to make the levees functional even if overtopped, to strengthen or upgrade the flood walls and levees, and to upgrade the pumping stations (ASCE Review Panel 2007, p. 78).
An important report was published by the American Society of Civil Engineers Hurricane Katrina External Review Panel, entitled The New Orleans Hurricane Protection System: What Went Wrong and Why (ASCE Review Panel 2007). The various reports prepared by the Interagency Performance Evaluation Task Force (IPET), entitled Performance Evaluation of the New Orleans and Southeast Louisiana Hurricane Protection System, are being published on the IPET website as they are released and revised, https://ipet.wes.army.mil/. There is a total of eight volumes. The Interim Final Volume I-Executive Summary and Overview (IPET 2007) is 147 pages long.