Hurricane Katrina of the 2005 Atlantic hurricane season was the costliest hurricane, as well as one of the five deadliest, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall. Hurricane Katrina formed over the Bahamas on August 23, 2005, and crossed southern Florida as a moderate Category 1 hurricane, causing some deaths and flooding there before strengthening rapidly in the Gulf of Mexico. The storm weakened before making its second landfall as a Category 3 storm on the morning of Monday, August 29 in southeast Louisiana. It caused severe destruction along the Gulf coast from central Florida to Texas, much of it due to the storm surge. The most severe loss of life and property damage occurred in New Orleans, Louisiana, which flooded as the levee system catastrophically failed, in many cases hours after the storm had moved inland. The federal flood protection system in New Orleans failed at more than fifty places. Nearly every levee in metro New Orleans was breached as Hurricane Katrina passed just east of the city limits. Eventually 80% of the city became flooded and also large tracts of neighboring parishes, and the floodwaters lingered for weeks. At least 1,836 people lost their lives in the actual hurricane and in the subsequent floods, making it the deadliest U.S. hurricane since the 1928 Okeechobee Hurricane. Economist and Crisis Consultant Randall Bell, brought into the area after the levee failures, writes in his book, Real Estate Damages, "Hurricane Katrina in 2005 was the largest natural disaster in the history of the United States. Preliminary damage estimates were well in excess of $100 billion, eclipsing many times the damage wrought by Hurricane Andrew in 1992." The storm is estimated to have been the costliest tropical cyclone in U.S. history.
The levee failures prompted investigations of their design and construction which belongs to the US Army Corps of Engineers as mandated in the Flood Control Act of 1965 and into their maintenance by the local Levee Boards (who prevented the Army Corps from building flood gates at the mouth of the drainage canals at Lake Pontchartrain ). There was also an investigation of the responses from federal, state and local governments, resulting in the resignation of Federal Emergency Management Agency director Michael D. Brown, and of New Orleans' Police Superintendent Eddie Compass. Conversely, the United States Coast Guard, the National Hurricane Center and National Weather Service were widely commended for their actions, accurate forecasts and abundant lead time. Four years later, thousands of displaced residents in Mississippi and Louisiana were still living in trailers.
Reconstruction of each section of the southern portion of Louisiana has been addressed in the Army Corps LACPR Final Technical Report which identifies areas to not be rebuilt and areas buildings need to be elevated. The Technical Report includes locations of possible new levees to be built; suggested existing levee modifications; "Inundation Zones"; "Water depths less than 14 feet, Raise-In-Place of Structures"; "Water depths greater than 14 feet, Buyout of Structures"; "Velocity Zones"; and "Buyout of Structures" areas for five different scenarios. The Corps of Engineers will submit the report to Congress for consideration, planning, and response in mid 2009.