2005 levee failures in Greater New Orleans
On August 29, 2005, there were over 50 failures of the levees and flood walls protecting New Orleans, Louisiana, and its suburbs following passage of Hurricane Katrina and landfall in Mississippi. The levee and flood wall failures caused flooding in 80% of New Orleans and all of St. Bernard Parish. Tens of billions of gallons of water spilled into vast areas of New Orleans, flooding over 100,000 homes and businesses. Responsibility for the design and construction of the levee system belongs to the United States Army Corps of Engineers; the responsibility of maintenance belongs to the local levee boards. The Corps hands components of the system over to the local levee boards upon completion. When Katrina struck on August 29, 2005, the project was between 60–90% complete. Four major investigations were conducted by civil engineers and other experts in an attempt to identify the underlying reasons for the failure of the federal flood protection system. All concur that the primary cause of the flooding was inadequate design and construction by the Corps of Engineers.
There were six major breaches in Orleans Parish:
- Three major breaches occurred on the Industrial Canal: one on the northeast side near the junction with Gulf Intracoastal Waterway and two on the southeast side along the Lower Ninth Ward, between Florida Avenue and Claiborne Avenue.
- On the west side of New Orleans, the 17th Street Canal levee breached below design specs on the New Orleans side near the Old Hammond Highway Bridge
- The London Avenue Canal in the Gentilly neighborhood breached on both sides – on the west side near Robert E. Lee Boulevard and on the east near the Mirabeau Avenue Bridge
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 a new Industrial Canal for waterborne commerce. Closure of the waterways resulted in a drastic lowering of the water table by the city's drainage system, causing some areas to settle by up to 8 feet 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 Corps of Engineers to design and construct flood control structures, along with levees, on the Mississippi River to protect populated areas from floods. It also affirmed the principle of local participation in federally funded projects but acknowledged that the $292 million already spent by local interests was sufficient to cover local participatory costs. It is instructive to note that, in addition, sovereign immunity was given to the Corps of Engineers 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.
Heavy flooding caused by Hurricane Betsy in 1965 brought concerns regarding flooding from hurricanes to the forefront. In response, the Congress passed the Flood Control Act of 1965 which mandated that henceforth, the Corps of Engineers is the agency responsible for design and construction of flood protection projects, to include those in Greater New Orleans. The local interests' role was maintenance once the projects were complete.
Also that year, Congress authorized the Lake Pontchartrain and Vicinity Hurricane Protection Project which reiterated the principle of local participation in federally funded projects. The project was initially estimated to take 13 years, but when Katrina struck in 2005, almost 40 years later, the project was only 60–90% complete with a revised projected completion date of 2015.
On August 29, 2005, flood walls and levees catastrophically failed throughout the metro area. Some collapsed well below design thresholds. Others collapsed after a brief period of overtopping caused scouring or erosion of the earthen levee walls. In April 2007, the American Society of Civil Engineers called the flooding of New Orleans "the worst engineering catastrophe in US History."
Levee and floodwall breaches
Many of the levee and floodwall failures were reported on Monday, August 29, 2005, at various times throughout the day. There were 28 reported failures in the first 24 hours and over 50 were reported in the ensuing days. A breach in the Industrial Canal, near the St. Bernard/Orleans parish line, occurred at approximately 9:00 a.m. CDT, the day Katrina arrived. Another breach in the Industrial Canal was reported a few minutes later at Tennessee Street, as well as multiple failures in the levee system, and a pump failure in the Lower Ninth Ward, near Florida Avenue.Local fire officials reported a breach at the 17th Street Canal levee shortly after 9:00 a.m. CDT. An estimated 66% to 75% of the city was now under water. The Duncan and Bonnabel Pumping Stations were also reported to have suffered roof damage, and were non-functional. Breaches at St. Bernard Parish and the Lower Ninth Ward were reported at 5:00 p.m. CDT, as well as a breach at the Hayne Blvd. Pumping Station, and another breach along the 17th Street Canal levee. By 8:30 p.m. CDT, all pumping stations in Jefferson and Orleans parishes were reported as non-functional.
At 10:00 pm CDT, a breach of the levee on the west bank of the Industrial Canal was reported, bringing of standing water to the area. At about midnight, a breach in the London Avenue Canal levee was reported.
The Orleans Canal about midway between the 17th Street Canal and the London Avenue Canal, engineered to the same standards, and presumably put under similar stress during the hurricane, survived intact because an incomplete section of floodwall along this canal which allowed water to overtop at that point, thus creating a spill way.
Investigations
Levee investigations
In the ten years following Katrina, over a dozen investigations were conducted. There was no federally ordered independent commission like those ordered after the September 11 terrorist attacks and after the BP Oil Spill in the Gulf. The only federally ordered study was convened and managed by the Army Corps of Engineers, the federal agency responsible for the flood protection's performance. A major independent study was conducted by the University of California at Berkeley. A second major study was sponsored by the Louisiana Department of Transportation led by Ivor van Heerden at Louisiana State University. Studies were also done by FEMA, the insurance industry, the National Research Council, the National Institute of Standards and Technology, and the Katrina Consolidated Lawsuit. All studies basically agreed on the engineering mechanisms of failure.The primary mechanisms of failure at the 17th Street Canal, London Avenue Canal and Industrial Canal were improper design of the canal floodwalls. The failure mechanism for the Industrial Canal was overtopping of levees and floodwalls by the storm surge. The primary mechanism of failure for levees protecting eastern New Orleans was the existence of sand in 10% of places instead of thick Louisiana clay. The primary mechanism of failure for the levees protecting St. Bernard Parish was overtopping due to negligent maintenance of the Mississippi River Gulf Outlet, a navigation channel, built and maintained by the Corps of Engineers.
A June 2007 report by the American Society of Civil Engineers in peer review panel concluded that the flooding in the Lakeview neighborhood and the Gentilly neighborhood was due to two engineering oversights.
The engineers responsible for the design of the canal levees and the I-walls embedded in them overestimated the soil strength, meaning that the soil strength used in the design calculations was greater than what actually existed under and near the levee during Hurricane Katrina. They made unconservative interpretations of the data: the soil below the levee was actually weaker than that used in the I-wall design. Another critical engineering oversight that led to the failure of the 17th Street Canal involves not taking into account the possibility of a water-filled gap which turned out to be a very important aspect of the failures of the I-walls around New Orleans. “Analysis indicate that, with the presence of a water-filled gap, the factor of safety is about 30 percent lower. Because a factor of safety of 1.3 was used for design, a reduction of 30 percent would reduce the factor of safety to approximately one: a condition of incipient failure.” This meant that the design included a safety factor of 30%, and could cope in theory with stresses 30% more than expected, but the error due to the water gap was about 30%, which immediately used up the entire safety margin, leaving no leeway in the design if any other excess stress occurred.
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. Engineers misjudged the strength of the peat which is from the remains of the swamp on which some areas of New Orleans in the 20th century were built. The shear strength of this peat was found to be very low and it had a high water content. According to Robert Bea, a geotechnical engineer from the University of California, Berkeley, 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."
The Federal study was initiated in October 2005, by Lt. Gen. Carl Strock, Chief of Engineers and the Commander of the Corps of Engineers; he established the Interagency Performance Evaluation Task Force to "provide credible and objective scientific and engineering answers to fundamental questions about the performance of the hurricane protection and flood damage reduction system in the New Orleans metropolitan area. IPET consisted of independent and recognized experts from the Universities of Maryland, Florida, Notre Dame, and Virginia Polytechnic Institute, the National Oceanic and Atmospheric Administration, the South Florida Water Management District, Harris County Flood Control District, the United States Department of Agriculture, and the United States Bureau of Reclamation as well as those from USACE.
IPET's final findings indicated that,
Criticism of the IPET Federal Investigation
The IPET's findings are challenged by Levees.org as lacking credibility since the USACE convened and managed the study and also chose and directly compensated its peer review team. The groups points out that eighty percent of the participants in IPET either worked for the Corps of Engineers or its sister agency Army Research and Development. The top three leaders all were Corps employees or past employees.The credibility of the IPET was also challenged in a 42-page letter to the American Society of Civil Engineers submitted by Dr. Ray M. Seed, co-chair of the ILIT study. Dr. Seed described an early intentional plan by the Corps of Engineers to hide their mistakes in the New Orleans flooding after Katrina and to intimidate anyone who tried to intervene. All of this was done with the help and the complicity of some at the ASCE, according to Dr. Seed.
Flood wall design
Investigators focused on the 17th Street and London Avenue canals, where evidence showed they were breached even though water did not flow over their tops, indicating a design or construction flaw. Eyewitness accounts and other evidence show that levees and flood walls in other parts of the city, such as along the Industrial Canal, were topped by floodwaters first, then breached or eroded.A preliminary report released on November 2, 2005, carried out by independent investigators from the University of California, Berkeley and the American Society of Civil Engineers stated that many New Orleans levee and flood wall failures occurred at weak-link junctions where different levee or wall sections joined together. This was not supported by later final studies.
A forensic engineering team from the Louisiana State University, using sonar, showed that at one point near the 17th Street Canal breach, the piling extends just below sea level, shallower than the Corps of Engineers had maintained. "The Corps keeps saying the piles were 17 feet, but their own drawings show them to be 10 feet, Ivor van Heerden said. "This is the first time anyone has been able to get a firm fix on what's really down there. And, so far, it's just 10 feet. Not nearly deep enough." The two sets of November tests conducted by the Corps of Engineers and LSU researchers used non-invasive seismic methods. Both studies understated the length of the piles by about seven feet. By December, seven of the actual piles had been pulled from the ground and measured. The Engineering News Record reported on December 16 that they ranged from 23' 3 1/8" to 23' 7 7/16" long, well within the original design specifications, contradicting the early report of short pilings.
They also found that homeowners along the 17th Street Canal, near the site of the breach, had been reporting their front yards flooding from persistent seepage from the canal for a year prior to Hurricane Katrina to the Sewerage and Water Board of New Orleans. However, no data exists confirming that the water was coming from the canal.
Other studies showed the levee floodwalls on the 17th Street Canal were "destined to fail" from bad Corps of Engineers design, saying in part, "that miscalculation was so obvious and fundamental," investigators said, they, "could not fathom how the design team of engineers from the Corps, local firm Eustis Engineering, and the national firm Modjeski and Masters could have missed what is being termed the costliest engineering mistake in American history."
Dr. Robert Bea, chair of an independent levee investigation team, has said that the New Orleans-based design firm Modjeski and Masters could have followed correct procedures in calculating safety factors for the flood walls. He added, however, that design procedures of the Corps may not account for changes in soil strength caused by the changes in water flow and pressure during a hurricane flood. Dr. Bea has also questioned the size of the design safety margins. He said the corps applied a 30% margin over the maximum design load. A doubling of strength would be a more typical margin for highway bridges, dams, off-shore oil platforms and other public structures. There were also indications that substandard concrete may have been used at the 17th Street Canal.
In August 2007, the Corps released an analysis revealing that their floodwalls were so poorly designed that the maximum safe load is only of water, which is half the original design.
A report released in August 2015 in the official journal of the World Water Council concluded the following:
Overtopping of levees in the Eastern New Orleans
According to Professor Raymond Seed of the University of California, Berkeley, a surge of water estimated at 24 feet, about 10 feet higher than the height of the levees along the city's eastern flank, swept into New Orleans from the Gulf of Mexico, causing most of the flooding in the city. He said that storm surge from Lake Borgne travelling up the Intracoastal Waterway caused the breaches on the Industrial Canal.Aerial evaluation revealed damage to approximately 90% of some levee systems in the east which should have protected St. Bernard Parish.
levee, with Katrina-related graffiti. Notice cracks in the flood wall joints. Operation and maintenance are the responsibility of local levee boards as mandated by the Flood Control Act of 1965
National Academy of Sciences Investigation
On October 19, 2005, Defense Secretary Donald Rumsfeld announced that an independent panel of experts, under the direction of the National Academy of Sciences, would convene to evaluate the performance of the New Orleans levee system, and issue a final report in eight months. The panel would study the results provided by the two existing teams of experts that had already examined the levee failures. The academy concluded that “the engineering of the levee system was not adequate. The procedures for designing and constructing hurricane protection systems will have to be improved, and the designing organizations must upgrade their engineering capabilities. The levees must be seen not as a system to protect real estate but as a set of dams to protect people. There must be independent peer reviews of future designs and construction.”Senate Committee hearings
Preliminary investigations and evidence were presented before the U.S. Senate Committee on Homeland Security and Governmental Affairs on November 2, 2005, and generally confirmed the findings of the preliminary investigations.On November 9, 2005, The Government Accountability Office testified before the Senate Committee on Environment and Public Works. The report cited the Flood Control Act of 1965, which authorized the U.S. Army Corps of Engineers to design and construct a flood protection system to protect south Louisiana from the strongest storms characteristic of the region.
Corps of Engineers admits problems with design
On April 5, 2006, months after independent investigators had demonstrated that the levee failures were not due to natural forces beyond intended design strength, Lt. Gen. Carl Strock testified before the U.S. Senate Subcommittee on Energy and Water that, "We have now concluded we had problems with the design of the structure." He also testified that the U.S. Army Corps of Engineers did not know of this mechanism of failure prior to August 29, 2005. The claim of ignorance is refuted by the National Science Foundation investigators hired by the Army Corps of Engineers, who point to a 1986 study by the corps itself that such separations were possible in the I-wall design. This issue is addressed again in a study released in August 2015 by J. David Rogers et al., who concluded that a misinterpretation of the 1986 study occurred apparently because the Corps had draped a tarpaulin over the gap that formed between the bases of the deflecting sheet piles and the soil in which they were embedded, so they did not see the gap. The tarpaulin was there for safety and to stop water that would seep through the interlocks. Failure to include the gap in interpretation of the test results introduced unconservatism in the final designs based on these tests. It allowed the use of shorter sheet piles, and reduced overall flood protection reliability.Nearly two months later, on June 1, 2006, the USACE finalized their report. The final draft of the IPET report states the destructive forces of Katrina were "aided by incomplete protection, lower than authorized structures, and levee sections with erodible materials.