After Hurricane Katrina on August 29, 2005, seven major investigations were conducted by civil engineers and other experts in an attempt to identify the cause of the flooding. Specifically, the investigators searched for the underlying reasons for the failure of protective system of levees and floodwalls encircling the city of New Orleans and the region. This system was called the Lake Pontchartrain and Vicinity Hurricane Protection Project (LPVHPP). All concurred that the primary cause of the failure was inadequate design and construction of the LPVHPP by the United States Army Corps of Engineers (Army Corps).Robertson, Campbell.
There were over 50 failures of the federally authorized LPVHPP (levees and flood walls protecting New Orleans, Louisiana, and two suburbs) while Hurricane Katrina passed to the east as a Category 3 hurricane on the Saffir–Simpson scale. The failures caused flooding in 80% of New Orleans, a small portion of Jefferson Parish and nearly all of St. Bernard Parish.
Responsibility for the design and construction of the LPVHPP belongs to the Army Corps. Responsibility for maintenance of completed sections of the project belongs to the local levee districts as stipulated in the Flood Control Act of 1965.
In September 2022, the Associated Press issued a style guide change to Hurricane Katrina stating that reporters when writing about the flooding in New Orleans should note that “…levee failures played a major role in the devastation in New Orleans. In some stories, that can be as simple as including a phrase about Hurricane Katrina’s catastrophic levee failures and flooding….”
On January 4, 2023, the National Hurricane Center (NHC) updated the Katrina fatality data based on Rappaport (2014). The new toll reduced the number by about one quarter from an estimated 1,833 to 1,392. The Rappaport analysis wrote that the 2005 storm "…stands apart not just for the enormity of the losses, but for the ways in which most of the deaths occurred." The same NHC report also revised the total damage estimate keeping Hurricane Katrina as the costliest storm ever––$190 billion according to NOAA's National Centers for Environmental Information.
Background
The original residents of New Orleans settled on the high ground along the Mississippi River. Later developments eventually extended to nearby Lake Pontchartrain, built upon fill to bring them above the average lake level. Navigable commercial waterways extended from the lake to downtown. After 1940, the state decided to close those waterways following the completion of the Inner Harbor Navigation Canal for waterborne commerce, which opened in 1923. Closure of the waterways resulted in a lowering of the water table by the city's drainage system, causing some areas to settle by up to 8 feet (2 m) due to the compacting and desiccation of the underlying organic soils.
After the Great Mississippi Flood of 1927, United States Congress passed the Flood Control Act of 1928 which authorized the Army Corps to design and construct flood control structures, including levees, on the Mississippi River to protect populated areas from floods. It also affirmed the principle of local participation in federally funded projects. In addition, sovereign immunity was given to the Army Corps under Section 3 of the Flood Control Act of 1928, which states “no liability of any kind would attach or rest upon the United States for any damage from or by floods or flood waters at any place, provided that if on any stretch of the banks of the Mississippi River it was impracticable to construct levees." 33 U.S.C. § 702c. Section 702c is sometimes referred as "Section 3 of the act," based on where it appears in the Public law.
Multiple levee failures, heavy flooding and losses exceeding $1 billion during Hurricane Betsy in 1965 raised concerns about flooding from hurricanes. In response, Congress passed the Flood Control Act of 1965 which authorized the Army Corps to design and construct the region's hurricane flood protection. The project was called the Lake Pontchartrain and Vicinity Hurricane Protection Project (LPVHPP).
The 1965 act stipulated the principle of local funding participation in the amount of 30 percent and also stipulated that the local levee districts are responsible for maintenance of the completed project. The LPVHPP was initially estimated to take 13 years, but when Katrina struck in 2005, parts of the project were 60–90% complete with a revised projected completion date of 2015.
Levee and floodwall breaches In the city of New Orleans there were six major breaches of the Lake Pontchartrain and Vicinity Hurricane Protection Project.
Three major breaches occurred on the Inner Harbor Navigation Canal (locally known as the Industrial Canal). A breach on the northeast side near the junction with the Gulf Intracoastal Waterway flooded eastern New Orleans. Two breaches on the southeast side between Florida Avenue and Claiborne Avenue combined into a single 1,000-foot wide hole that allowed stormwater into the adjacent Lower Ninth Ward. On the western edge of New Orleans near Hammond Highway, a breach opened in the 17th Street Canal levee. Floodwater flowed through a hole that became 450 feet wide, flooding the adjacent Lakeview neighborhood. The London Avenue Canal in the Gentilly region, breached on both sides; on the west side near Robert E. Lee Boulevard and on the east near Mirabeau Avenue.
There were 28 reported failures in the first 24 hoursStaff Writer. "Timeline: Who Knew When the Levees Broke." National Public Radio. February 10, 2006. and over 50 were reported in the ensuing days. Before dawn on Monday August 29, 2005, waves overtopped and eroded the Mississippi River-Gulf Outlet Canal levees in St. Bernard Parish. At about 5:00 am, a 20-foot section of floodwall, called a "monolith," on the east side of the Industrial Canal, breached and released flood water into the Lower Ninth Ward. By 6:30 a.m. Central Time Zone (North America), levees along the Gulf Intracoastal Waterway, bordering the south side of eastern New Orleans, also overtopped and breached.Van HeerdenI. Ll.Kemp G. P. Mashriqui et al. (2006). The Failure of the New Orleans Levee System during Hurricane Katrina. Final Team Louisiana Forensics Report to Louisiana Department of Transportation and Development, December 2006. Baton Rouge, LA, USA. p 71-72
On the western edge of New Orleans, between 6 and 7:00 a.m., a 20-foot monolith on the east side of the London Avenue Canal failed and allowed water over 10 feet deep into the Fillmore Gardens neighborhood. At about 6:30 a.m., on the western edge of the city, several monoliths failed on the 17th Street Canal releasing stormwater into the Lakeview neighborhood. Local fire officials reported the breach. An estimated 66% to 75% of the city was then under water. In nearby Jefferson Parish, the Duncan and Bonnabel Pumping Stations were also reported to have suffered roof damage, and because they were unmanned, were non-functional.Staff Writer. "Timeline: Who Knew When the Levees Broke." National Public Radio. February 10, 2006.
At approximately 7:45 a.m, a much larger second hole opened up in the Industrial Canal just south of the initial breach. Floodwaters from the two breaches combined to submerge the entire Lower Ninth Ward in over 10 feet of water. Between 7 and 8:00 am, the west side of the London Avenue Canal breached, in addition to the east side, and flooded the adjacent mixed-race neighborhood of homeowners.
The Orleans Avenue Canal midway between the 17th Street Canal and the London Avenue Canal, engineered to the same standards as the latter two, survived intact due the presence of an unintended 100-foot-long ‘spillway,’ a section of legacy wall that was significantly lower than the adjacent floodwalls.Volume 1, USACE Interagency Performance Evaluation Taskforce, 44.
Storm surge also triggered breaches in about 20 places on the Mississippi River-Gulf Outlet Canal ("MR-GO") resulting in flooding of Saint Bernard Parish and the east bank of Plaquemines Parish.
Levee failure investigations
Summary According to the American Geosciences Institute, there were twenty Senate and House Committee meetings on Hurricane Katrina in the six months following the breach event. These took place between September 14, 2005, and February 2, 2006. There was no federally ordered independent commission like those ordered after the September 11 attacks and the Deepwater Horizon oil spill. "If the evidence points to human error, it may be difficult for the Corps to point the finger at itself or contractors it employed," said Mark Dombroff, a Washington lawyer and former chief of the torts branch of the Justice Department. In the next decade, there were seven major levee failure investigations.
Senate and House Committee hearings
On September 28, 2005, the Government Accountability Office testified before the House Subcommittee on Energy and Water Development, Committee on Appropriation. Their report cited the Flood Control Act of 1965 which authorized the Army Corps, from then forward, to be responsible for design and construction of the hurricane flood protection system enveloping New Orleans and also St. Bernard Parish. This was called the Lake Pontchartrain and Vicinity Hurricane Protection Project and also stipulated that the Orleans Levee District and the Lake Borgne Levee District retained the role of maintenance and operations after project completion.
On November 2, 2005, preliminary investigations and evidence were presented before the U.S. Senate Committee on Homeland Security and Governmental Affairs which generally confirmed the findings of the preliminary investigations."Hurricane Katrina: Why Did the Levees Fail? ." U.S. Senate (Hearing Report for the Committee on Homeland Security and Governmental Affairs). November 2, 2005.
On April 5, 2006, Lt. Gen. Carl Strock testified before the U.S. Senate Subcommittee on Energy and Water that "the Corps neglected to consider the possibility that floodwalls atop the 17th Street Canal levee would lurch away from their footings under significant water pressure and eat away at the earthen barriers below. We did not account for that occurring." Strock said it could be called a design failure. He also testified that the Army Corps did not know of this mechanism of failure prior to August 29, 2005.
Independent Levee Investigation Team (ILIT) The first major study was conducted by the University of California, Berkeley and funded by the National Science Foundation. The three co-chairs were Dr. Robert Bea, Dr. Raymond Seed and Dr. J. David Rogers. The final report was released on July 31, 2006.
The investigators found that soil borings in the area of the 17th Street Canal breach showed a layer of peat starting at about below the surface, and ranging from about to thick. McQuaid, John; Marshall, Bob.
"Officials knew about weak soil under levee ." Times Picayune. October 22, 2005. The shear strength of this peat was found to be very low and it had a high water content. According to co-chair Dr. Bea, the weak soil made the floodwall very vulnerable to the stresses of a large flood. "At 17th Street, the soil moved laterally, pushing entire wall sections with it. ... As Katrina's storm surge filled the canal, water pressure rose in the soil underneath the wall and in the peat layer. Water moved through the soil underneath the base of the wall. When the rising pressure and moving water overcame the soil's strength, it suddenly shifted, taking surrounding material – and the wall – with it."McQuaid, John. "Swamp peat was poor anchor, engineer says ." Times Picayune. October 15, 2005.