I haven't heard what the actual sustained winds in New Orleans were on Monday, but I doubt they were Cat 4, since the storm passed to the east of the city by at least a couple dozen miles and the storm was a Cat 3 at landfall in Mississippi.
And I don't think there was any rescue plan in place in advance at all. New Orleans has a "let the good times roll" attitude about everything. As long as it could keep the tourist dollars rolling in, the rest of the city was pretty much left to itself.
I will go look to see if I can find that graphic you're referring to.
Of course the issue was not the winds, except to the degree that it raised the lake water level. That combined with the surge, which was right up the entry to the lake from the Gulf, was what caused the levees to breech, and the rest is history.