I'm not defending Bush, and am surprised, as is Will, that his numbers took a big hit, compared with the fallout from other of his actions.
To address the point of the thread, was he lying, i,e, intentionally saying something which he knew not to be true? Well, we know it wasn't true. As for his intent, I have to conclude that he knew his statements to be false.
Why would he lie? Maybe he was making a judgment call that there would be less harm in that than in tellling the truth. If he had said flat out "New Orleans is screwed if it takes a direct hit from a cat 4 or 5 hurricane" panic would certainly have followed.
On the other hand, maybe people in the city would have taken the evacuation warning more seriously. The problem with this line of thinking, for me anyway, is that the federal government didn't jump immediately in on the disaster with both feet, which suggests (go figure) Bush and others in the administration didn't have the smarts to figure out what they were dealing with.
However you look at it, New Orleans has been a disaster waiting to happen. Here's a link to an article in Civil Engineering Magazine which ran a few years before the storm. It gives a lot of historical background, and talks about the billions of dollars in expenditures required to put into effect a potential solution to the hurricane disaster scenario:
http://www.pubs.asce.org/ceonline/ce.../0603feat.html
The following excerpt from it is particularly relevant, as it speaks of the state of affairs commonly known to those, including politicians, having to address the issue:
"In the Flood Control Act of 1965, passed shortly after Hurricane Betsy pummeled New Orleans, Congress appropriated funds to increase the height of the levees around the northern side of the city, where Lake Pontchartrain ominously abuts what used to be swampland but today is suburbia. With help from a meteorologist from the National Weather Service, Corps engineers determined a wind speed and pressure that they felt closely characterized Hurricane Betsy. The work was done before the development of the Saffir-Simpson scale, which today is used to categorize hurricanes. At the time Corps engineers called their approximation a standard project hurricane (SPH), equivalent to what today would be called a fast-moving category 3 storm."
Matthew, you asked "How could anyone have possibly anticipated this devastation when nothing of this magnitude had occurred prior to this?" The answer, as the above article illustrates, is that many people did, and for many years prior to Katrina.