Katrina :: Storm Effects
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Effects of the Storm :: Hurricane Katrina :: Levee Breaches
As of mid-day Monday, August 29, the eye of Hurricane Katrina had swept northeast and spared New Orleans the brunt of the storm. The City seemed to have escaped most of the catastrophic wind damage that was predicted.
However, at 11 a.m. the National Weather Service reported that a levee broke on the Industrial Canal...
http://en.wikipedia.org/wiki/Effect_of_Hurricane_Katrina_on_New_Orleans
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Levee Breaches
As of mid-day Monday, August 29, the eye of Hurricane Katrina had swept northeast and spared New Orleans the brunt of the storm. The City seemed to have escaped most of the catastrophic wind damage that was predicted.
However, at 11 a.m. the National Weather Service reported that a levee broke on the Industrial Canal, a 5.5 mile (9 km) waterway that connects the Mississippi River to the Intracoastal Waterway, near the St. Bernard-Orleans Parish line (Tennessee St.) and 3 to 10 feet (1 to 3 m) of flooding was possible. This area, also known as the 9th Ward, reported 3 pump failures.
On August 30 at 1:30 a.m. CDT, CNN (via the Vice President of Tulane University Medical Center) reported that a wall on the 17th Street Canal, which normally drains into Lake Pontchartrain, suffered a two city-block wide breach.
John Hall, spokesman for the Army Corps of Engineers, later said that the floodwall on top of the 17th Street Canal Levee had been overtopped by the storm surge. The water cascading over the wall eventually undermined the wall base, causing it to collapse outwards. Repairs were complicated by the presence of the low Hammond Highway bridge and a hurricane barrier on the Lake Pontchartrain side of the breach, which impeded access by barges and heavy equipment.
The 17th Street Canal Levee is on the border of Metairie and New Orleans proper, and when it collapsed it flooded most of the city under as much as 25 feet (8 m) of water. This breach allowed the water of Lake Pontchartrain, which at the time was some six feet (2 m) above sea level, to flow downward into northern New Orleans proper, which lies between two and ten feet (1 to 3 m) below sea level. A 200-foot breach was confirmed by New Orleans Fire Department officials to CNN at 3:16 a.m. CDT on August 30 [15].
At 6:30 p.m. WWL-TV announced that the effort to sandbag (ongoing since 2 p.m.) the breach in 17th St. canal levee at the Hammond Highway bridge had failed, and it was expected that the pumping station at that location would fail.
At 10 p.m. CDT on August 30, Mayor Ray Nagin reported on WDSU that the planned sandbagging of the 17th Street Levee breach failed because National Guard Blackhawk helicopters that were expected at the breach were diverted to save some people in a church, and also reported that another 9 feet (3 m) of water was expected to fill the entire City. This means that even the French Quarter would flood within about 12 hours, up to the level of Lake Pontchartrain, three feet (1 m) above sea level. The failure to sandbag would add at least an additional four weeks to drain the city. He estimated that it would take about four months before the City would be habitable.
On August 30, the London Avenue Canal floodwall was breached at 6100 Pratt Drive, according to the Army News Service
NASA satellite imagery released on August 30 showed that Lakes Pontchartrain and Maurepas had substantially overflowed and had nearly blended into a single lake separated only by a narrow strip of land. Significant flooding along local rivers was also indicated
On Friday, September 2, it was estimated that ad hoc levee repairs would be complete by Sunday, September 4 and, once the City's system of pumps can be repaired and supplied with power, that unwatering the City would then take a minimum of 35 days (mid October) and up to 80 days (end of November) for some areas. Access from the lake to the 17th Street Canal was blocked, stopping water flow despite the canal breach still being open.
By Saturday, September 3, it had been discovered that the pumps used to drain New Orleans were no longer manufactured, so that the damaged parts would have to be remanufactured instead of replaced as had been hoped. It was estimated that at least a week would be required to dry out the pumps before repair could be attempted. Any residential structure submerged for two weeks will likely require demolition.
On September 4, Brigadier General Robert Crear of the US Army Corps of Engineers said that they had succeeded in closing off the 17th Street Canal. He added that it would take between 36 and 80 days to complete the task of emptying New Orleans of flood water. New estimates on September 10 indicate that it may be as few as three weeks before water is drained from the city, because of drier weather, favorable winds, and the use of deliberate breaches in the lower levees.
http://en.wikipedia.org/wiki/Effect_of_Hurricane_Katrina_on_New_Orleans
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