Hmm most wise builders have a 3 to 4 foot high concrete fuel cell mount pedestal and generator mount type pedestal now days, to help prevent some of these problems, especially at critical data centers. Henry Sean Donelan wrote:

If I recall, during hurricane Hugo a Sprint CO flooded. They kept the water from coming in the doors, but didn't have a snorkal for the generator.

Although its great fun to discuss different disasters which can hit buildings, a fundamental principle is a you can't protect a single building, even a bunker, from everything.