It's harder to find exactly what would constitute overtopping. The comment from Anonymous indicates that 20 feet would mean overtopping. Thus, based on what I can figure as an amateur, my house missed getting flooded by a little more than 4.5 feet of surge.
I don't really know exactly how much more storm that would take. The other issue, of course, is that those measurements assume that the levees wouldn't break. After all, the 17th Street Canal did not overtop; it failed. Like everyone else, I look at levees with new eyes now. They're not infallible.
Interestingly, the Corps' website says that the record level for Carrollton was 21.27 Feet on Apr 25, 1922. Does this mean that there was a flood there in 1922? If anyone out there knows, please educate me. Obviously, if anyone out there has real expertise in this area, I welcome an education in this area. I'd love to know what it would take to flood my house on Camp Street in Uptown New Orleans.
You can get the data yourself at this link.