Hurricane Katrina was a large Category 5 Atlantic hurricane that caused over 1,800 deaths and $125 billion in damage in late August 2005, particularly in the city of New Orleans and the surrounding areas. It was at the time the costliest tropical cyclone on record and is now tied with 2017's Hurricane Harvey.

The storm was the twelfth tropical cyclone, the fifth hurricane, and the third major hurricane of the 2005 Atlantic hurricane season, as well as the fourth-most intense Atlantic hurricane on record to make landfall in the contiguous United States.

Katrina also had a profound impact on the environment. The storm surge caused substantial beach erosion, in some cases completely devastating coastal areas. The damage from Katrina forced the closure of 16 National Wildlife Refuges. The storm caused oil spills from 44 facilities throughout southeastern Louisiana, which resulted in over 7 million US gallons (26,000 m3) of oil being leaked.

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