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Hurricane & Storm Damage Risk
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Outfall Canals and Closure Structures
Outfall Canals
During hurricanes and tropical storms, three outfall canals drain water from portions of New Orleans northward into Lake Pontchartrain. These outfall canals are critical elements in New Orleans’ flood control system. Levees line the sides of the canals, and floodwalls are situated on the top of each levee. See an animated video about the outfall canals here. |
The 17th Street Canal extends 2.4 miles north from Pump Station #6 to Lake Pontchartrain along the boundary between Orleans and Jefferson parishes. Hurricane Katrina caused a breach in the floodwall along the east side of the canal just south of Hammond Highway, resulting in flooding of the Lakeview area and parts of Metairie in neighboring Jefferson Parish.
The Orleans Avenue Canal, between the 17th Street and London Avenue Canals, runs from Pump Station #7 to Lake Pontchartrain.
The London Avenue Canal extends 4 miles north from Pump Station #3 to Lake Pontchartrain about halfway between the Orleans Avenue Canal and the Inner Harbor Navigation Canal (also known locally as the Industrial Canal). Hurricane Katrina caused a floodwall breach along the west side of the canal near Robert E. Lee Boulevard and another breach along the east side of the canal near Mirabeau Avenue, resulting in flooding of the Gentilly area in New Orleans.
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New Orleans Outfall Canals |
During Hurricane Katrina, breaches occurred at the 17th Street and London Avenue Canals when water and waves pushing against the outside (water side) of the floodwalls (I-walls) caused the walls to shift, essentially splitting each levee into two pieces. Material on the protected side of the levee was unable to withstand the pressure from the forces opposite the floodwall and gave way, allowing water, intensified by the force of the waves, to spill into the protected areas.
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The Corps repaired and improved all three canals beyond pre-Katrina risk reduction levels before the start of the 2006 hurricane season.
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Interim Closure Structures and Permanent Pumps
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In addition to repairing and improving the canal walls, temporary gated closure structures were built at the mouths of the three outfall canals prior to the start of the 2006 hurricane season. These gated structures stay open during normal, non-tropical conditions.
When storm surge threatens to exceed the maximum operating water level of a canal, the Corps will close the gates and turn on the pumps. Pumps push rainwater around the closed gates and into Lake Pontchartrain. The closed gates prevent storm surge from entering the canals and going back into the city. When the surge recedes, the Corps will reopen the gates and normal drainage will resume.
These structures were built with a limited design life, and they will be replaced with permanent canal closures and pumps. The contract is expected to be awarded in the spring of 2011, and construction will be complete in the fall of 2014. |
Outfall Canal Wall Remediation
17th Street Canal
London Avenue Canal
Orleans Avenue Canal
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The Corps will also begin remediating the outfall canal walls in December 2010 to ensure that they meet post-Katrina requirements. As a secondary benefit, the remediated walls will support the requirements of the Sewerage & Water Board of New Orleans in removing rain water unimpeded from the city, now and in the future.
Methods of remediation include deep soil mixing for strengthening canal levees, adding embankment at the levee crown to reduce floodwall stick-up, constructing stability berms to strengthen canal levees and installing sheet piles to deflect seepage.
During construction, the Corps and its contractor will reduce negative construction impacts by watering the roads to minimize dust and by using the silent sheet pile Press-In method to limit noise and vibrations.
Construction will be complete in June 2011.
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Contact
Webmaster
504-862-1606
webmaster-mvn@usace.army.mil
Updated 8/29/2011
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