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Levee failures in Greater New Orleans, 2005

2007 Schools Wikipedia Selection. Related subjects: Natural Disasters; Recent
History

   Sketch of New Orleans (shaded grey), indicating the locations of the
   principal breaches in the levees/floodwalls (dark blue arrows). Red
   dots show locations of deaths.
   Enlarge
   Sketch of New Orleans (shaded grey), indicating the locations of the
   principal breaches in the levees/floodwalls (dark blue arrows). Red
   dots show locations of deaths.
            Hurricane Katrina

   2005 Atlantic hurricane season

   General
     * Timeline
     * Meteorological history
     * Preparations
          + New Orleans preparedness

   Impact
     * Economic effects
     * Political effects
     * Criticism of gov't response
     * Social effects
     * Effects by region
          + Effects on Mississippi
          + Effects on New Orleans
               o Levee failures
               o Infrastructure repairs
               o Reconstruction

   Relief
     * Disaster relief
     * International response

   Analysis
     * Alternative theories
     * Historical context
     * Media involvement

   Other wikis
     * Commons: Katrina images
     * Wikinews: Katrina stories
     * Wikisource: Katrina sources

   In 2005, as a result of Hurricane Katrina, there were extensive
   failures of the levees and flood walls protecting New Orleans,
   Louisiana and surrounding communities. There were also extensive
   subsequent investigations by civil engineers to attempt to identify the
   underlying reasons for the failures.

   The Mississippi River Gulf Outlet ("MR-GO") breached its levees in
   approximately 20 places, flooding much of New Orleans East, most of
   Saint Bernard Parish and the East Bank of Plaquemines Parish. The major
   levee breaches in the city included breaches at the 17th Street Canal
   levee, the London Avenue Canal, and the wide, navigable Industrial
   Canal, which left approximately 80% of the city flooded. There were
   three major breaches at 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, engineers investigated the
   possibility that a failure in the design, construction, or maintenance
   caused much of the flooding. Some investigations point to the
   possibility of a weakening of the soil beneath the foundations of the
   flood walls due to storm water, which would indicate that a major
   design flaw made during the construction of the levees had been a major
   cause of the failures due to the storm.

Background

   Vertical cross-section of New Orleans, showing maximum levee height of
   23 feet (7 m) at the Mississippi river on the left and 17.5 feet (5 m)
   at Lake Pontachartrain on the right.
   Enlarge
   Vertical cross-section of New Orleans, showing maximum levee height of
   23 feet (7 m) at the Mississippi river on the left and 17.5 feet (5 m)
   at Lake Pontachartrain on the right.

   Flooding due to rain and storms has long been an issue since the New
   Orleans' early settlement due to the city's location on a delta marsh,
   much of which sits below sea level. The city is surrounded by the
   Mississippi River to the south, Lake Pontchartrain to the north, and
   Lake Borgne to the east. Construction of the levees along the River
   began soon after the city was founded, and more extensive river levees
   were built as the city grew. The levees were originally designed to
   prevent damage caused by seasonal flooding. Today, the modern 17th
   Street and London Avenue Canals are used for drainage, while the wide,
   navigable Industrial Canal is used for shipping. The heavy flooding
   caused by Hurricane Betsy in 1965 brought concerns regarding flooding
   from hurricanes to the forefront.

   Shortly after hurricane Betsy, the Army Corps of Engineers designed a
   Lake Pontchartrain Hurricane Barrier to shield the city with flood
   gates like those that protect the Netherlands from the North Sea.
   Congress provided funding and construction began in 1971, but work
   stopped in 1977 when a federal judge ruled, in a suit brought by Save
   Our Wetlands, that the Corps' environmental impact statement was
   deficient. In 1985, after nearly a decade of court battles, the Corps
   scrapped the plan, and decided on reinforcing the city’s levee system
   instead.

   There were many predictions of hurricane risk in New Orleans before
   Hurricane Katrina in August, 2005. In 2001, the Houston Chronicle
   published a story which predicted that a severe hurricane striking New
   Orleans, "would strand 250,000 people or more, and probably kill one of
   10 left behind as the city drowned under 20 feet of water. Thousands of
   refugees could land in Houston." Many concerns also focused around the
   fact that the city's levee system was only designed for hurricanes of
   no greater intensity than category 3. As it turned out, Katrina was
   Category 3 when it made landfall and most of New Orleans experienced
   Category 1 or 2 strength winds. However, due to the slow moving nature
   of the storm in its pass over New Orleans, several floodwalls lining
   the shipping and drainage canals in New Orleans collapsed and the
   resulting flood water from Lake Ponchartrain inundated the city within
   the two days following the storm, causing costly damage to buildings
   and resulting in many deaths.

   Furthermore, the region's natural defenses, the surrounding marshland
   and the barrier islands, have been dwindling in recent years.

Levee and floodwall breaches

   Breach in 17th Street Canal levee in New Orleans, Louisiana, on August
   31, 2005. (NOAA)
   Enlarge
   Breach in 17th Street Canal levee in New Orleans, Louisiana, on August
   31, 2005. (NOAA)
   Severely damaged homes in piles of silt near the upper London Avenue
   Canal breach.
   Enlarge
   Severely damaged homes in piles of silt near the upper London Avenue
   Canal breach.

   Most of the levee failures were reported on Monday, August 29, 2005, at
   various times throughout the day. Overall, approximately 28 levee
   failures were reported. A breach in the Industrial Canal, near the St.
   Bernard/ Orleans parish line, occurred at approximately 9:00 AM CST,
   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 17th Street Canal levee
   at about 12:00 PM CST, 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 from Lake Pontchartrain, was reported at 10:30 PM CST. 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 overtopped at this point, thus reduced the
   pressure against the wall.

Investigations

Preliminary investigations

   During the 6 weeks following Katrina, preliminary investigations were
   carried out by the Army Corps of Engineers, the American Society of
   Civil Engineers, as well as by independent parties.

   Possible failure mechanisms being investigated by engineers included
   the overtopping of levees and floodwalls by the storm surge,
   consequential undermining of flood wall foundations or other weakening
   by water of the wall foundations, the storm surge pressures exceeding
   the strength of the floodwalls, as well as impact by vessels such as
   barges which had broken free of their moorings (such as the ING 4727
   barge which may have crashed through a levee in the Industrial Canal
   near the Lower Ninth Ward).

   A preliminary report by the American Society of Civil Engineers on an
   independent investigation has concluded that the flooding in the
   Lakeview neighbourhood was caused by the soil of the levees giving way
   and not by water overtopping the flood walls. The statement said that
   there was evidence that a section of the levee embankment that
   supported the flood wall had moved approximately 45 feet laterally.
   Inspectors also found evidence of the dirt levee moving at the London
   Avenue breach. However, many miles of levees worked as they should even
   though the water got over their tops.

   Soil borings have been made in the area of the 17th Street Canal
   breach. These borings show a layer of peat which starts about 15 to 30
   feet below the surface and ranges from about 5 feet to 20 feet thick.
   The peat is from the remains of the swamp on which the low area of New
   Orleans (near Lake Ponchartrain) were built. The shear strength of this
   peat was found to be very low, and to have a high water content.
   According to Prof. Robert Bea, a geotechnical engineer from the
   University of California, Berkeley, this would make 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 peat layer appears to be about 1000 feet wide. It is not clear if
   it was properly taken into account when the levees were built. The
   flood walls consist of a concrete cap on a sheet pile base driven 17.5
   feet deep at 17th Street Canal. A deeper piling would have anchored the
   flood wall in much stronger soil.

Floodwall design

   Investigators are focusing on the 17th Street and London Avenue canals
   because evidence shows they were breached even though water did not
   flow over their tops. That could indicate a design or construction
   flaw. Eyewitness accounts and other evidence shows 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. Many
   of the 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, by independent investigators from the
   University of California, Berkeley, and the American Society of Civil
   Engineers (ASCE).

   In the investigation by the American Society of Civil Engineers, it was
   found that when the geological borings were made in 1981 prior to
   construction of floodwalls along the 17th Street Canal, they revealed
   to both the Army Corps of Engineers officials as well as the
   contractors who designed and built the wall the nature of the weak
   layer of soft soil that would lie under the base of flood walls'
   foundation 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 meters), and the design documents
   show calculations were made with the wall base at 12.8 feet (3.9
   meters). According to a New Orleans engineer, the depth was apparently
   increased later, to a depth of 17 feet (5.1 meters), and this is what
   was built. However, investigations using sonar by a forensic
   engineering team from the Louisiana State University showed that at one
   point near the 17th Street Canal breach, the piling extends just 10
   feet (3 meters) below sea level, 7 feet (2.1 meters) shorter 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," 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." Other reports confirmed that construction on the London
   Avenue and Industrial Canal levees was similarly below these stated
   standards. They also found evidence that homeowners along the 17th
   Street Canal near what would be the site of the breach had been
   reporting on persistent seepage from the canal flooding their yards for
   a year prior to Hurricane Katrina. Other studies showed that 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 that 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. But engineers studying the
   levees also say that other, unknown factors, including structural
   problems in the walls, could also have contributed to the breaches.

   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

   Portion of the flood wall atop 17th Street Canal levee, with
   Katrina-related graffiti. Notice cracks in the flood wall joints.
   Enlarge
   Portion of the flood wall atop 17th Street Canal levee, with
   Katrina-related graffiti. Notice cracks in the flood wall joints.

   Poor maintenance practices were also found along miles of other levees.
   A possible trigger of the 17th Street Canal levee breach may have been
   the fall of a large oak tree, planted too close to the base of the
   levee. A similar scenario may have played out on the London Avenue
   Canal. Burrowing animals created large tunnels that undermined already
   weak foundations. Maintenance and inspection are the responsibility of
   local levee boards.

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 have already examined the levee failures.

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 confirm the preliminary investigations
   described above.

   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 5, 2006, months after independent investigators had
   demonstrated that 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,
   however, 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.

   Nearly two months later, June 1, 2006, the US ACE finally
   unequivicaolly admitted responsbility for the tragedy in New Orleans
   with the release of the completed report. The Final Draft of the IPET
   report states that the destructive forces of Katrina were not contained
   by but were "aided by incomplete protection, lower than authorized
   structures, and levee sections with erodible materials."

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