There were shelters that allowed pets, and pet carriers were provided since many people didn't evacuate when Katrina hit because they'd didn't want to leave their pets behind.

Article in USA Today

I don't know if people won't evacuate next time. It could happen. I believe if Nagin had waited until they were SURE Gustav would cram NOLA before issuing the order, it would have been too late to get people out. It was a tough call and I respect him for making it.