Bells tolled through the streets of New Orleans at 9:38 am (1438 GMT) on Tuesday, marking the minute a year ago that the first torrent of water from Hurricane Katrina burst through a failing levee system and began inundating the city.
President George W Bush was on hand for a memorial service and to meet with residents on the anniversary and the city planned to mark the day in its own unique way.
A crowd of about 50 gathered and rang hand bells at City Hall, while across the city in the Lower Ninth Ward, one of the areas hardest hit by flooding, hundreds met to march toward downtown to press for the 'right to return' home, shorthand for a plea to give more help to those most in need.
"We're all together but we're not all back," marcher Robert Stark said, emphasising the unity of spirit among friends and relatives scattered around the United States.
Some danced, others beat drums and still others lit candles next to new 15-foot-high flood walls protecting a now-empty field where blocks of houses were smashed by a flood torrent.
Other marches will muster brass bands to play dirges to honour the dead and up-tempo standards to celebrate life in jazz funeral-style processions that the city adores. Prayer and memorial services were planned throughout the day.
Katrina killed about 1,500 people across four states, hitting hardest in Louisiana and Mississippi, according to the National Hurricane Center. It was the most expensive natural disaster in US history, flooding 80 per cent of New Orleans.
Buras, Louisiana, the tiny town where Katrina made landfall on August 29, 2005, was one of the first in the region to mark the storm's anniversary as about a hundred people gathered for a minute of silence at a volunteer fire department station that is still missing walls wrecked by Katrina.
Life between levees
About 3,300 people lived in Buras before Katrina and the fishing town has been slow to repopulate. However, white government travel trailers with returning families have been popping up between two levees on the tenuous piece of land about a half mile wide between the Mississippi River and the Gulf of Mexico.
Some of the New Orleans marches will pass the Superdome stadium where thousands took shelter during the worst of the storm and then waited days to be rescued as the city flooded.
Earlier in the week some feared that Tropical Storm Ernesto, now headed toward Florida, would target New Orleans around the anniversary of Katrina.
About 450,000 people lived in New Orleans before the storm and only about half of them have returned. Many former city residents are packed into surrounding suburbs where more houses and apartments survived.
The city has debated for weeks how to mark a year's passage and whether to focus on the losses or survival. A fireworks plan was dropped but New Orleans clung to the need for music.
On the first of a two-night 'anti-versary' concert to raise funds for displaced musicians, organiser Jeff Beninato lamented on Monday that donations were faltering to his Web site, www.nomrf.org, the New Orleans Musician's Relief Fund, as the Katrina disaster faded in people's minds.
Few have been able to survive without a sense of humour, especially the more than 100,000 families packed into travel trailers, a point made by singer Leah Chase as she thanked anti-versary directors for inviting her.
"Anything, any time that gets me out of that trailer is a treat," she said before breaking into "Do You Know What It Means to Miss New Orleans".