Revelers are gathering in New Orleans, Louisiana Tuesday to celebrate Mardi Gras, the U.S. city's first since Hurricane Katrina battered the region last August.     

Crowds for the parades and street parties are far smaller than in past years, but many residents and tourists say they must keep New Orleans' vibrant traditions alive.

Parades will thread through the city's streets, as people decked out in Mardi Gras colors of purple, gold and green try to catch beaded necklaces and souvenirs
thrown from floats.    

The New Orleans visitors bureau says this is the 150th anniversary of Mardi Gras parades in the city.

Mardi Gras, the final day of the joyful Carnival season, is celebrated in some countries with large Roman Catholic populations. The season precedes Lent, the somber Christian observance leading up to Easter.

Some information for this report was provided by AP.