The city suffered from the effects of a major hurricane on and after August 29,
2005, as Hurricane Katrina made landfall in the gulf coast near the city. In the
aftermath of the storm, what has been called "the largest civil engineering disaster in the history of the United States" flooded the majority of the ciy when the levee and floodwall system protecting New Orleans failed.
On August 26th, tracks which had previously indicated the hurricane was heading towards the Florida Panhandle shifted 150 miles westward, initially centering on Gulfport/Biloxi, Mississippi and later shifted further westward to the Mississippi/Louisiana state line. The city became aware that a possible major hurricane hit was possible and issued voluntary evacuations on Saturday, August 27. Interstate 10 in New Orleans East and Jefferson and St. Charles parishes was converted to all-outbound lanes heading out of the city as well as Interstates 55 and 59 in the surrounding area, a manuver known as "contraflow."
In the Gulf of Mexico, Katrina continued to gain strength as it turned northwest, then north towards southeast Louisiana and southern Mississippi. On the morning of Sunday, August 28, Katrina was upgraded to a top-notched Category 5 hurricane. Around 10 am, Mayor Nagin issued a mandatory evacuation of the entire city, the first such order ever issued in the city's history. An estimated 1 million people evacuated from Greater New Orleans and nearby areas before the storm. However, some 20% of New Orleans residents were still in the city when the storm hit. This included people who refused to leave home, those who felt their homes were adiquate shelter from the storm, and people without cars or without financial means to leave. Some took refuge in the Superdome, which was designated as a "shelter of last resort" for those who could not leave.
The eye of the storm missed heart of the city by only 20-30 miles, and strong winds ravaged the city, shattering windows, spreading debris in many areas, and bringing heavy rains and flooding to many areas of the city. 
The situation worsened when levees on four of the city's canals were breeched. Storm surge was funneled in via the Mississippi River Gulf Outlet which breached in multiple places. This surge also filled the Industrial Canal which breeched either from the surge or the effects of being hit by a loose barge (the ING 4727). The London Avenue Canal and the 17th Street Canal were breached by the elevated waters of Lake Pontchartrain. Some areas that initially seemed to suffer little from the storm found themselves flooded by rapidly rising water on 30 August. As much as 80% of the city - much of which is below sea level - was flooded, with water reaching a depth of 25 feet (7.6 meters) in some areas. Water levels were similar to those of the 1909 Hurricane, but as many areas which were swamp or farmland in 1909 had become heavily settled since, the effects were massivly worse. The most recent estimates of the damage from the storm, by several insurance companies, are 10 to 25 billion USD,[2] while the total economic loss from the disaster has been estimated at 100 billion USD. If the storm damage totals reach the estimated maximum, it will surpass Hurricane Andrew as the costliest hurricane in United States history.
