The Baton Rouge radar "storm totals" make it look that under 2" of rain fell in New Orleans, but they are surrounded by '2-6"' areas - including onto the lake.
http://radar.weather.gov/radar/latest/DS.80stp/si.klix.shtml
I'm not quite sure of where this comes from though: when I hit "refresh" a while ago, expecting to see more orange and red on the map, some of the general color scheme seemingly went to lower totals. I had not saved the earlier one for comparison, so I'm not sure what's up with that...
Whatever, if N.O. area doesn't get smacked by significantly more rain, that will sure be a help.
Some of the models project Rita making a 360 around NO and then crossing back into the Gulf.