Katrina 20th anniversary: progress and ongoing risks for New Orleans

Twenty years after Hurricane Katrina struck the Gulf Coast on Aug. 29, 2005, New Orleans and the region it shattered are marking the anniversary amid a mixture of commemoration, pride in recovery efforts and warnings about unfinished risks. The storm made multiple U.S. landfalls, including a Category 3 strike on southeast Louisiana, unleashed a catastrophic storm surge that overwhelmed flood defenses and left vast sections of New Orleans under water, displacing hundreds of thousands and causing economic losses measured in the hundreds of billions of dollars.

Katrina formed as Tropical Depression Twelve on Aug. 23, intensified rapidly over the Gulf of Mexico and reached peak winds near Category 5 strength before weakening slightly prior to the August 29 landfalls. Federal and scientific investigators later attributed the scale of the disaster not only to the storm itself but to levee and floodwall failures; roughly 80 percent of New Orleans flooded, with some neighborhoods inundated to depths approaching 20 feet. Estimates of the death toll vary by source, with counts commonly cited near 1,400 and other tallies reaching as high as about 1,800.

Survivors and first responders...