Where are you getting this 36 hours business? The Mayor made the "Mandatory" evacuation order on Sunday. The time stamp on the AP story announcing it was 3:46 PM, Sunday the 28th. The hurricane hit Monday morning, ~ 8AM IIRC. Even if the AP story was delayed hitting the wires, it was less than 24 hours. The state of emergency was in place since the 26th, but the mandatory order came too late to have any chance of success.
As to the Army Corps of Engineers budget and spending, read the Washington Post article I linked. It is discussed in detail. Make sure you read it all, it is two pages. Here is the link again:
http://www.washingtonpost.com/wp-dyn/content/article/2005/09/07/AR2005090702462.html
If you care, you can read the "City of New Orleans Comprehensive Emergency Management Plan, Annex I: Hurricanes" here:
http://www.cityofno.com/portal.aspx?portal=46&tabid=26
Make your own decisions on if it was followed.
Tom