New Orleans’ Levee Failures Chalston Layacan Elizabeth Lenker Jamie Mellies.

New Orleans’ Levee Failures

Chalston LayacanElizabeth Lenker

Jamie Mellies

Outline

• Background– Hurricane Katrina– Levee System– Destruction

• Failures– General Problems– 4 Mechanisms of Failure

• Future– Immediate Reconstruction– Long Term Goals

• List of References

Hurricane Katrina

• August 29, 2005• One of the strongest storms

ever to hit the US coast• Hit Gulf of Mexico and

shores of Louisiana, Mississippi, and Alabama

• Killed over 1,000 in Louisiana resulting in over $27.7 billion in damage

New Orleans’ Levee System

• What is a levee?– A protective barrier built along the banks of any

body of water to protect the neighboring land from being flooded

• Levees and floodwalls were built along canals, Lake Pontchartrain, and the Mississippi River to protect against flooding.

Types of Levees

• Earthen– A ridge of dirt along a body of water,

equivalent to a bank

• I-Wall– An earthen levee with linked steel pilings

driven into the ground and a concrete wall above ground

– Stronger than an earthen levee

Where the Levees Were Breached

The Destruction

• Many of the levees and floodwalls collapsed or were overtopped by water, which allowed billions of gallons of water into New Orleans and flooded the city.

• Levees collapsed at approximately 50 locations.• Out of 284 miles of levees and floodwalls, 169 miles

were damaged.• If the levees and floodwalls had not failed, 2/3 of the

deaths would not have occurred. • The catastrophic failure of New Orleans’ hurricane

protection system represents one of the nation’s worst disasters ever.

Poorly Designed Levees

• Levees were only designed to withstand a Standard Project Hurricane. (set in the 1950s)

• Levees were built on and made of soft, erosion-prone soils.• Foundations were not sunk deep enough into the ground.

At the 17th Street canal, the pilings were supposed to be 17 feet below the ground but were only 10 feet.

• Measurement problems and subsidence caused some levees to be built several feet lower than designed.

Four Mechanisms of Levee Failure

1. Overtopped earthen levee

2. Overtopped I-wall levee

3. Sliding soil under I-wall levee

4. Water flowing through sand layer under I-wall levee

Overtopped Earthen LeveesAll levees without I-walls were overtopped by the storm.

The levee was completely washed away in some cases.

Levees built with sand, silt, or by hydraulic fill were damaged the most.

Obliterated Levee(along Mississippi River-Gulf Outlet)

Overtopped I-Wall Levees

• Water flowing over the levee eroded the earth on the protected sides of the levees.

• Water washed away the soil near the foundation of the I-wall, weakening the foundation.

• Water then pushed over the top of the levees causing a collapse.

Overtopped I-Wall Levees

Overtopped I-Wall Levee(Industrial Canal, East Bank, South Breach)

WALL

Industrial Canal, East Bank, South Breach

(due to I-wall levee overtopping)

I-Wall Levees – sliding soil

• In the design, the engineers underestimated the strength of the soil.

• They also did not account for the presence of a water-filled gap.

17th Street Canal Failure (due to sliding soil)

London Ave Canal North Breach(due to sliding soil)

Industrial Canal, East Bank, North Breach(due to sliding soil)

I-Wall Levees – water flowing through sand layer

• Engineers didn’t account for the water seeping into the sand layer under the levee and coming up the other side.

London Ave Canal South Breach (caused by water flowing through sand layer)

Immediate Reconstruction

• Task Force Guardian– U.S. Army Corps of Engineers project– Floodwall repair and replacement– Levee repair to a height of 15 ft– Levee armoring – reinforcing slopes with

riprap or concrete to prevent erosion when the levee is overtopped

Long term goals• Task Force Hope

– U.S. Army Corps of Engineers project– Ultimate goal: integrated levee and floodwall system

able to withstand category 5 storm– Restoring wetlands, which will act as natural buffer– Levee armoring– Permanent gated structures for canals– Channel control-floating flood control gates on the

Mississippi River-Gulf outlet

List of References• Articles

– “Keeping the Waters at Bay” by Thomas Hayden U.S. News World Report Feb. 27, 2006

– “Little Good News on Levees and Wetlands” by Meghan Stromberg Planning Vol. 72, Issue 1Jan. 2006

• Websites– “Katrina’s Levee Failures: Cleansing the Corps” by Anthony Kendall Jan. 17,

2006 http://www.anthonares.net/2006/01/katrinas-levee-failures-cleansing.html – “The New Orleans Hurricane Protection System: What Went Wrong and Why: a

Report” by the American Society of Civil Engineers Hurricane Katrina External Review Panel. http://www.asce.org/files/pdf/ERPreport.pdf

• Pictures– www.fishindog.com/images/katrina1.jpg– bbsnews.net/bbsn_photos/topics/hurricane_katrina/

uscg_new_orleans_under_water20050829.jpg– www.katrina-hurricane.biz/images/katrina-hurricane-pic3.jpg– http://www.asce.org/files/pdf/ERPreport.pdf– www.killedthat.com/wp-content/uploads/2007/08/hurricane-katrina.jpg