FORENSIC ENGINEERING IN NEW ORLEANS AFTER HURRICANE KATRINA

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FORENSIC ENGINEERING IN NEW ORLEANS AFTER
HURRICANE KATRINA

• TURNING THE 29-30 AUGUST DISASTER IN NEW ORLEANS
  AND THE GULF COAST OF THE USA (LOUISIANA,
  MISSISSIPPI, ALABAMA, AND FLORIDA) INTO NEW
  OPPORTUNITIES

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HURRICANE KATRINA
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NEW ORLEANS
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LEVEE RECONSTRUCTION

• THE LEVEE SYSTEM IS CENTRAL TO THE RECOVERY AND
  RECONSTRUCTION OF NEW ORLEANS.
• UNDERSTANDING THE CAUSES OF LEVEE FAILURE DURING
  HURRICANE KATRINA AND STATE-OF-THE-ART REPAIR OF
  THE FLAWS ARE OF THE HIGHEST PRIORITY.

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A 300 KM (200 MI) LEVEE SYSTEM PROTECTS NEW
ORLEANS
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NEW ORLEANS LEVEE SYSTEM

• BEFORE SETTLEMENT 0F 1-2 M (2-3 FT) IN SOME
  LOCATIONS, THE LEVEES WERE 5.1 M (17 FEET) HIGH
  INITIALLY.
• THIS HEIGHT IS CONSIDERED SUFFICIENT TO RESIST
  THE STORM SURGE OF A CATEGORY 3 HURRICANE.

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DEVASTATION FROM HURRICANE KATRINA

• FLOODING, NOT HIGH WINDS, INFLICTED MOST OF THE
  DEVASTATION IN NEW ORLEANS .
• 80 PERCENT OF NEW ORLEANS WAS FLOODED FROM FOUR
  MAJOR AND DOZENS OF SMALLER BREACHES IN THE LEVEE
  SYSTEM.
• OVER 100,000 HOMES WERE INUNDATED.

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FLOODING IN NEW ORLEANS
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FLOODING IN NEW ORLEANS
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FORENSIC ENGINEERING AFTER HURRICANE KATRINA

• The US Army Corps of Engineers conducted the
  equivalent of a forensic investigation at the
  levees and floodwalls of New Orleans, drilling
  into the earth to examine the soil and reviewing
  the design of the structure.

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FORENSIC ENGINEERING AFTER HURRICANE KATRINA

• With the help of computer models and visual
  evidence, scientists and engineers at Louisiana
  State University's Hurricane Center concluded
  that Katrina's storm surges did not overtop the
  levees.

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FORENSIC ENGINEERING AFTER HURRICANE KATRINA

• A "debris line" indicated that the top height of
  Katrina's waves was at least 1 m (4 ft) below
  the crest of Lake Pontchartrain's levees.
• The breached floodwalls near Lake Ponchartrain
  showed no signs of overtopping no splattering
  of mud, no drip lines and no erosion at their
  bases.

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FORENSIC ENGINEERING AFTER HURRICANE KATRINA

• The pattern of destruction behind the breached
  zones was consistent with a localized "pressure
  burst," rather than widespread overtopping.

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LEARNING FROM THE REVIEW

• A five-foot layer of peat lies beneath the entire
  levee system.
• The layer of peat played a major role in the
  levee failure, becoming soft and wet, moving,
  and eventually bursting as the water level rose
  during the hurricane.

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CONCLUSIONS FROM FORENSIC ENGINEERING

• The floodwaters simply pushed the entire levee
  structure out of its way, allowing the water to
  flow out of Lake Ponchartrain into New Orleans.

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CONCLUSIONS FROM FORENSIC ENGINEERING

• The conclusion is that faulty design, inadequate
  construction, or some combination of the two, are
  the likely causes of the breaching of the
  floodwalls along the 17th Street and London
  Avenue canals.
• These two breaches caused most of the flooding in
  New Orleans.

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FLAWS IN CONSTRUCTION THAT NEED TO BE FIXED

• USE OF WEAK, POORLY COMPACTED SOIL IN THE INITIAL
  CONSTRUCTION.
• INADEQUATE NUMBER OF STEEL PILINGS TO ANCHOR
  FLOOD WALLS TO SUBSURFACE STRATA.
• OVERESTIMATING THE GEOLOGIC CAPACITY OF THE PEAT
  LAYER.

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LEVEE RECONSTRUCTION
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REPAIRING FLAWS IN THE LEVEE SYSTEM
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LEVEE RECONSTRUCTION HAS STARTED

• 1.6 BILLION WAS REDIRECTED TOWARDS IMMEDIATE
  RECONSTRUCTION OF THE LEVEE SYSTEM.
• 240 MILLION WAS REDIRECTED TOWARDS RESTORATION
  OF COASTAL STORM BUFFERS AND WETLANDS.

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HURRICANE KATRINA LOSS OF BARRIER ISLANDS
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COST OF IMPROVED SAFETY

• THE COST OF REBUILDING LEVEES IN NEW ORLEANS TO
  RESIST A CATEGORY 5 HURRICANE IS ESTIMATED AT
  2.5 BILLION.
• IN ADDITION, THE STATE OF LOUISIANA HAS REQUESTED
  20 BILLION TO CONSTRUCT NEW STORM BARRIERS
  AND IMPROVE DRAINAGE SYSTEMS.