A historic event

Katrina was a historic event for several reasons, including its intensity and scale, impact on area levee failures, the massive flooding it caused in New Orleans, and the storm’s lingering impact on the city’s population.

The National Oceanic and Atmospheric Administration (NOAA) reported that, at its peak intensity as a Category 5 storm, Katrina’s wind field comprised tropical storm-force winds extending 200 miles from its eye, and hurricane-force winds 90 miles out. Katrina was “not only extremely intense but also exceptionally large,” according to NOAA.

DEATHS,

the third-most from any U.S. hurricane since 1900

IN INSURED LOSSES,

the most insured losses from any single event in history and triple those of the previous recordholder, 1992’s Hurricane Andrew ($35 billion)

PEOPLE DISPLACED

from Alabama, Louisiana, and Mississippi

FEET OF STORM SURGE,

the highest recorded for an Atlantic hurricane

DECLINE IN REAL GDP

for the New Orleans-Metairie metropolitan statistical area in the two years after Katrina

IN ECONOMIC LOSSES

Sources: Swiss Re, National Hurricane Center, National Weather Service, Center for American Progress, Federal Reserve Bank of St. Louis

Though the storm weakened to a Category 3 hurricane before striking Louisiana, it maintained its immense size. Sustained surface-level winds created record-high storm surge to the east of Katrina’s eye, and significant water levels to its west. NOAA reported high-water measurements of:

  • At least 28 feet in Mississippi.
  • 15 to 19 feet in eastern New Orleans and neighboring parishes.
  • 10 to 14 feet on the southern shore of Lake Pontchartrain.

This storm surge put extreme stress on New Orleans’ levee system and floodwalls. Erosion on the back side of levees caused overtopping, and a catastrophic floodwall failure occurred along the city’s 17th Street Canal, a critical impact point. The resulting flood inundated 80% of the city of New Orleans, with up to 20 feet of water, according to NOAA.

The failure of the city’s pumping system also contributed to the loss and delay of water removal. The Army Corps of Engineers, which has been responsible for New Orleans’ levee system since 1965, indicated all floodwaters were finally removed from New Orleans on October 11, 43 days after Katrina made landfall.

All of this contributed to more than $100 billion in insured losses (in 2024 dollars), according to Swiss Re and other sources, making Katrina the costliest natural disaster in history for insurers. (See Figure 1.)

One unanticipated measure of Katrina’s severity was its impact on New Orleans’ population. The storm quickly overwhelmed the city’s ability to provide emergency services, leading to devastating images of city residents sheltering amid chaos in the Louisiana Superdome. Businesses and homes were destroyed, leading many to flee the city and state.

In 2005, the city of New Orleans had nearly 455,000 residents, a number that fell to about 209,000 in the year following Katrina, according to U.S. Census Bureau data compiled by Neilsberg Research. (See Figure 2). As of 2023, the urban population was 346,000 — well below the pre-Katrina population.

For businesses, this has meant fewer customers and a smaller talent pool, effectively constraining New Orleans’ economic growth.

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