| Levee Failures In Greater New Orleans, 2005 |
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In 2005, there were extensive failures of the Levee s and flood walls protecting New Orleans, Louisiana and surrounding communities. Five investigations (three major and two minor) 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 designed by the US Army Corps of Engineers. In total, the federal flood protection system protecting greater New Orleans failed in 53 places. The .'' October 4 , 2005 . Three major breaches occurred on the Industrial Canal ; one on the upper side near the junction with MR-GO, and two on the lower side along the Lower Ninth Ward , between Florida Avenue and Claiborne Avenue. The 17th Street Canal Levee was breached on the lower (New Orleans West End) side inland from the Old Hammond Highway Bridge, and the London Avenue Canal breached in two places, on the upper side just back from Robert E. Lee Boulevard, and on the lower side a block in from the Mirabeau Avenue Bridge. Flooding from the breaches put the majority of the city under water for days, in many places for weeks. In the aftermath of Hurricane Katrina, five investigation teams studied the failure of the hurricane protection system that led to the failures, and thus most of the flooding. All five studies basically agree on the mechanisms of levee failures, and all agree that the system designed by the US Army Corps of Engineers was a system in name only. BACKGROUND See Also: Drainage in New Orleans Hurricane preparedness for New Orleans The original residents settled on the high ground along the Mississippi River. Later developments eventually extended to nearby Lake Pontchartrian 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 these waterways since there was a new Industrial Canal for waterborne commerce. Once these waterways were closed, the water table was drastically lowered by the city's drainage system and some areas settled up to 8 feet (2 m) due to the consolidation of the underlying organic soils. After 1965, the US Army Corps built a levee system around a much larger geographic footprint that included previous marshland and swamp. The average elevation of the city is between 1 and 2 feet below sea level. There are no residential areas of the city that are currently more than 10 feet (3 m) below sea level. The heavy flooding caused by Hurricane Betsy in 1965 brought concerns regarding flooding from hurricanes to the forefront. That year, Congress gave the US Army Corps of Engineers sole authority for the design and construction of the flood protection in Greater New Orleans in the Pontchartrain Hurricane Protection Project. The local interests' role was maintenance once the projects were complete. When authorized, this Mandate was projected to take 13 years to complete. When Katrina struck in 2005, the project was between 60-90% complete and the projected date of completion was estimated to be 2015, nearly 50 years after it first gained authorization. To put that in perspective, President Theodore Roosevelt's construction of the Panama Canal , one of the largest and most difficult engineering projects ever undertaken, took 10 years. On August 29, 2005, flood walls and levees catastrophically failed throughout the metro area. Many collapsed well below design thresholds (17th Street and London Canals). Others collapsed after a brief period of overtopping ( Industrial Canal) caused by “scouring” or erosion of the earthen levee walls – an egregious design flaw. The American Society of Civil Engineers refers to the flooding of New Orleans as the worst engineering catastrophe in US History. {Link without Title} LEVEE AND FLOODWALL BREACHES Levee in New Orleans, Louisiana , on August 31 2005 , showing the innundated Lakeview neighborhood on the right and the largely dry Metairie side on the left.. (NOAA)]] breach.]] Most of the Army Corps-built levee failures were reported on Monday, , the day Katrina hit. Another breach in the Industrial Canal was reported a few minutes later at Tennessee Street, as well as multiple failures in the levee system, as well as a pump failure, in the Lower Ninth Ward , near Florida Avenue. Local fire officials reported a breach at the , though there was some confusion among FEMA officials over whether this was an actual breach, or overtopping. The Duncan and Bonnabel Pumping Stations were also reported to have taken roof damage, and were non-functional. Breaches at St. Bernard and the Lower Ninth Ward were reported at 5:00 PM CST , as well as a breach at the Haynes Blvd. Pumping Station, and another breach along the 17th Street Canal levee. By 8:30 PM CST , all pumping stations in Jefferson and Orleans parishes were reported as non-functional. At 10:00 PM CST , a breach of the levee on the west bank of the Industrial Canal was reported, bringing 10 feet of standing water to the area. A quarter-mile breach in the levee near the 17th Street Canal, 200 yards (200 m) from . An estimated 66% to 75% of the city was now under water. At about midnight, a breach in the London Avenue Canal levee was reported. Interestingly enough, the Orleans Canal , about midway between the 17th Street Canal and the London Avenue Canal, supposedly engineered to the same standards, and presumably put under similar stress during the Hurricane, survived intact. An incomplete section of floodwall along this canal allowed water to overtop at this point, thus reducing the pressure against the wall. INVESTIGATIONS Preliminary investigations In the 17 months following Katrina five investigations were carried out. The only Congressionally ordered study was sponsored and managed by the Army Corps Of Engineers . Two major independent studies were done by the University of California at Berkeley and the Louisiana State University. Two minor studies were done by FEMA and the insurance industry. All five studies basically agree on the engineering mechanisms of failure. The failure mechanisms engineers investigated included overtopping of levees and floodwalls by the storm surge, consequential undermining of flood wall foundations or other weakening by water of the wall foundations, and the storm surge pressures exceeding the strength of the floodwalls. A preliminary report by the American Society of Civil Engineers on an independent investigation concluded the flooding in the Lakeview neighborhood was caused by the soil of the levees giving way, not by water overtopping the flood walls. Soil borings in the area of the 17th Street Canal breach show a layer of ) were built.McQuaid, John; Marshall, Bob. " Officials knew about weak soil under levee ." ''.'' October 15 , 2005 . The peat layer appears to be about 1,000 feet (300 m) wide. It is not clear if it had been properly taken into account when the levees were built. The floodwalls consist of a concrete cap on a Sheet Pile base driven 17.5 feet (5.3 m) deep at 17th Street Canal. A deeper piling would have anchored the flood wall in much stronger soil. Floodwall design Investigators focused on the 17th Street and London Avenue canals because evidence shows they were breached even though water did not flow over their tops, indicating a design or construction flaw. Eyewitness accounts and other evidence show 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. Many New Orleans levee and floodwall failures in the wake of Hurricane Katrina occurred at weak-link junctions where different levee or wall sections joined together, according to a preliminary report released on .'' November 2 , 2005 . The American Society of Civil Engineers investigation found that geological borings made in 1981, prior to construction of floodwalls along the 17th Street Canal, revealed the nature of the weak layer of soft soil that lay under the base of flood walls foundations of steel piling. "According to the analysis, they've got the soil strength test. It doesn't show exactly the input for the analysis, but assuming they used it and came out with factors of safety, it's showing the numbers are safe. So it leaves an open-ended question as to why the flood wall failed." said Peter Nicholson, a geotechnical engineer from the University of Hawaii who is heading up an American Society of Civil Engineers team looking at the levees. The original design for the steel sheet foundations for the flood walls showed a proposed depth of 10 feet (3 m), and design documents show calculations were made with the wall base at 12.8 feet (3.9 m). According to a New Orleans engineer, the depth apparently was later increased to 17 feet (5.1 m), and this is what was built. However, a forensic engineering team from the .'' November 30 , 2005 . They also found that homeowners along the 17th Street Canal, near the site of the breach, had been reporting their yards flooding from persistent seepage from the canal for a year prior to Hurricane Katrina. Other studies showed the levee floodwalls on the 17th Street Canal were, "destined to fail,", from bad Army 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." It is likely the Katrina storm surge created unusual subterranean pressures under the walls. Those pressures appear to have made soil under the Sheet Pile weaker so that it gave way, moving the steel sheet-pile-and-concrete walls along with it. Engineers studying the levees also say other, unknown factors, including structural problems in the walls, could also have contributed to the breaches. Professor Bea has said that the design firm, New Orleans-based Modjeski and Masters, could have followed correct procedures in calculating safety factors for the flood walls. He added, however, that design procedures of the Army Corps may not account for changes in soil strength caused by the changes in water flow and pressure during a hurricane flood. Prof. 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 sub standard concrete may have been used at the 17th Street Canal. The two sets of November tests conducted by the Army Corps 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' 31/8" to 23' 77/16" long, well within the original design specifications, contradicting the early report of short pilings. The suitability of the original design specifications, however, continues to be contested. Overtopping of levees in the east According to Professor Raymond Seed of the ) '' University Of California, Berkeley .'' November 2 , 2005 . Aerial evaluation revealed damage to approximately 90% of some of the levee systems in the east which should have protected St. Bernard Parish . Levee maintenance levee, with Katrina-related graffiti. Notice cracks in the flood wall joints.]] Maintenance and inspection are the responsibility of local levee boards, but the levee failures were not due to maintenance, but rather to design flaws that routine maintenance would not have detected. National Academy of Sciences Investigation On .'' October 19 , 2005 . Senate Committee hearings Preliminary investigations and evidence were presented before the '' (Hearing Report for the Committee on Homeland Security and Governmental Affairs). November 2 , 2005 . 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. In his written evidence to the committee, Ivor van Heerden, from Louisiana State University , concluded, "Most of the flooding of New Orleans was due to man’s follies. Society owes those who lost their lives, and the approximately 100,000 families who lost all, an apology and needs to step up to the plate and rebuild their homes, and compensate for their lost means of employment. New Orleans is one of our nations jeweled cities. Not to have given the residents the security of proper levees is inexcusable." U.S. Army Corps of Engineers Admits Fault On .'' April 6 , 2006 . Nearly two months later, June 1, 2006, the USACE finally and unequivocally admitted responsibility for the events in New Orleans with the release of the completed 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." SEE ALSO
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