In fact, it is arguable that there is no such thing as a natural disaster.
Hurricanes and other natural hazards have always happened and always will.
They only become disasters when they interact with the built environment or
life support systems. In the case of Katrina, cities were built and
coastlines settled with the knowledge that these areas were vulnerable to
severe hurricanes. The disaster was therefore human-caused. The problem
with calling events natural disasters is that the word "natural" leaves the
impression that the disasters cannot be prevented, which, of course, is
false. The hazards cannot be prevented, but we can prevent them from
becoming disasters.