Like wise, it only takes one event laid on by nature that exceeds the specified design criteria of whatever permaculturefix you've got in place, and you're screwed.  Guess we should all just roll over and die then, right?

Yep, only the scale of the disaster is different.  Buddy people have been producing (including reproducing) and consuming without limits while drawing down finite resources for several centuries now - stuffing up the natural world in the process, it doesn't matter what technofixes you try to institute to alleviate the symptoms of all that producing and consuming going on, eventually there will be a collapse and die-off when the resources that enabled our overshoot (like fossil fuels) are exhausted.  All technofixes do in the context of perpetual growth in a finite world is ensure that the collapse and die-off will be even more resounding when it comes, as there will be more people, infrastructure, and GDP being supported at the final ecological reckoning.  Doesn't matter what you and I want or think as these trends of exponential growth and consumption are continuing unabated, and will continue to do so as virtually all people in the world are clamouring for more development (production and consumption) not less.  Worldwide population control is politically impossible, and no one will willingly agree to reduce their living standards in order to conserve finite resources and the biosphere for the benefit of future generations and the other species.  

The "specified design criteria" þ were NOT exceeded during Katrina.

Alan, whether by accident or design the levy walls were breached, and that is the point.  If it wasn't meant to be there in the first place, was poorly designed, or is merely addressing the effects of overproduction and over-consumption rather than the overproduction and over-consumption itself, you're just delaying the inevitable.  Nature will always produce an event which is greater than the specified design criteria - for there are no technofixes for the problems generated by perpetual growth in a finite world.  You just allow more people to exist, more infrastructure and GDP to be supported before the inevitable day of reckoning, and this was the lesson of Katrina.