"I cannot see a scenario that would cause large scale evacuation of Las Vegas (e.g. a hurricane)."

Water coming into Vegas isn't usually a problem, if you don't try to cross the flooded roads.

Water NOT coming into Vegas would be the first disaster that came to my mind. It's a city of two million residents plus tourists. If the water supply was cut off or contaminated, you would have a ghost town. If a bit of drinking water was available, the price would be astronomical.

But I doubt that even a military operation could bring enough water in to keep that many people alive.

sue