This week marks Mardi Gras, the trademark celebration that, to a certain extent, defines New Orleans in the public mind. But the festival happens in a city still heavily affected by the natural and man-made disaster of Hurricane Katrina. Three-and-a-half years after Katrina's flood overtopped the city's levees, there is good and bad news about the New Orleans' struggle to recover. While hurricane rebuilding has insulated the city somewhat from the national economic downturn, most of New Orleans' neighborhoods are far from recovered from Katrina's devastation. Many districts still have barely more than half their pre-storm population, and the worst-hit area, the Lower Ninth Ward, is less than 20% re-occupied.

In the years following Katrina, the Brookings Institution (a Washington-based think tank) has issued statistical reports twice a year to document the city's status. The latest edition of the report, "The New Orleans Index, January 2009," is posted at the Brookings website.

The good news is that New Orleans has so far escaped the worst brunt of the fallout from the global financial meltdown. Although housing starts have slowed and the credit crunch is stalling some work, the report says, "On balance ... the the New Orleans economy is adding jobs and relatively few homes have entered foreclosure."

However, the report goes on to say that, "the massive destruction from Hurricane Katrina remains widespread, dwarfing the rebuilding that is underway. Hundreds of streets are still in disrepair. Tens of thousands of residential, commercial, and institutional buildings remain damaged and unoccupied."

In a few higher, drier, and more affluent parts of the city, population levels are now at, or even above, their pre-Katrina levels. But less fortunate districts are in worse condition. This map from the Brookings report shows the variation in population return.

The less populated parts of the city, north of the river, represent locations that were both economically worse off before the storm, and more badly flooded during and after the storm. In these areas, thousands of vacant addresses remain — some repaired but unoccupied, some abandoned, and some demolished, leaving nothing but overgrown vacant lots. "In Orleans and St. Bernard parishes, 69,727 and 15,188 residential addresses, respectively, were unoccupied as of September 2008," says the Brookings report. Again, the greatest number of empty addresses can be found in the poorest parts of town.

Thousands of visitors may view the ghost-town blocks of the Lower Ninth Ward this week during Mardi Gras. But you don't have to travel there to see it — as of August 2008, Google Maps now provides "street view" imagery of most of New Orleans, including the largely empty Ninth Ward.

Not much has changed since last summer, and in general the Google Maps street-view images show New Orleans pretty much the way it still is. But the starting place of our tour is an exception: this is 1744 Tennessee, in the Lower Ninth Ward.

At this location, there is no longer an empty lot — there's a new occupied home, occupied by a smiling homeowner (see the photo by Flickr.com member "werdsnave"), designed by KieranTimberlake and built under the auspices of Brad Pitt's "Make it Right" foundation.

Progress, obviously, is incremental. We'll check back with you next Mardi Gras.