[Let me begin by expressing my heartfelt condolences to the survivors of our nation's most devastating natural disaster to date. I can't imagine the pain and the loss they must be experiencing.]
It's clear that many of the people living in those Mississippi coast towns like Waveland and Ocean Springs and Biloxi and Gulfport were unable to comprehend the magnitude of the danger to their persons and property that Hurricane Katrina represented as it churned towards them. What could these people, and also knowledgeable people in authority, have done to better inform themselves of the threat they faced? For one thing, they could've used some arithmetic, backed up by graphical illustrations. What follows is a very simple example.
1 gallon of water weighs 8.33 pounds. 1 cubic foot of water contains about 7.5 gallons, and so weighs about 62.5 pounds. This means that a column of water only 8 feet high, 1 foot wide and 1 foot deep weighs about 500 pounds.
Now let's suppose that the width of the average beachfront house facing the Gulf of Mexico was 70 feet (that's perhaps not too far off). What is the weight of a column of water 8 feet high, 70 feet wide and (say) 1 mile deep (i.e., stretching 1 mile out into the Gulf)? It's easy to calculate: just multiply out
Since water is an incompressible fluid, to be struck by a 92,000 ton column of it could be even more devastating than being struck by the Stennis (steel crumples and gives way to some degree; water does not). And note that we're not even considering the kinetic energy (that is, the energy of motion) of our column of water as it comes ashore in the storm surge. We're also ignoring the likelihood that considerably more than a mile of water stretching out into the Gulf is going to come ashore in such a surge.
If the average person were asked whether he thought that his house could withstand a direct hit by a 92,000 ton aircraft carrier, his answer would be an instantaneous "No!". So why does this same person believe that his house could withstand a direct hit by a 92,000 ton column of water? Well, he probably doesn't believe that; rather, it's likely that he doesn't know that that's the threat he's facing! And whose fault is that? In the land of personal responsibility, it's his, of course. But that doesn't mean that his elected representatives couldn't have done a better job of informing him and his neighbors of the threat they faced.
One last calculation. What is the weight of a column of water 20 feet high, 100 miles wide and stretching 2 miles out into the Gulf of Mexico? Answer: 6,969,600,000,000 pounds (that is, almost 7 trillion pounds), or 3,484,800,000 tons (roughly, 3.5 billion tons). I'll leave it as an exercise for the reader to find an appropriate graphic illustrating a storm surge of this magnitude.