Investigations of levee failures during Hurricane Katrina

Seven major investigations were conducted by civil engineers and other experts in an attempt to identify the underlying reasons for the failure of the Lake Pontchartrain and Vicinity Hurricane Protection Project (LPVHPP) on August 29, 2005. All concurred that the primary cause of the failure was inadequate design and construction by the United States Army Corps of Engineers (Army Corps).

There were over 50 failures of the federally authorized LPVHPP (levees and flood walls protecting New Orleans, Louisiana, and two suburbs) while Hurricane Katrina passed to the east as a Category 3 hurricane on the Saffir–Simpson scale. The failures caused flooding in 80% of New Orleans, a small portion of Jefferson Parish and nearly all of St. Bernard Parish.

Responsibility for the design and construction of the LPVHPP belongs to the Army Corps. Responsibility for maintenance of completed sections of the project belongs to the local levee districts as stipulated in the Flood Control Act of 1965.

In September 2022, the Associated Press issued a style guide change to Hurricane Katrina stating that reporters when writing about the flooding in New Orleans should note that “…levee failures played a major role in the devastation in New Orleans. In some stories, that can be as simple as including a phrase about Hurricane Katrina’s catastrophic levee failures and flooding….”

On January 4, 2023, the National Hurricane Center (NHC) updated the Katrina fatality data based on Rappaport (2014). The new toll reduced the number by about one quarter from an estimated 1,833 to 1,392. The Rappaport analysis wrote that the 2005 storm "…stands apart not just for the enormity of the losses, but for the ways in which most of the deaths occurred." The same NHC report also revised the total damage estimate keeping Hurricane Katrina as the costliest storm ever––$190 billion according to NOAA's National Centers for Environmental Information.