First, lets discuss the most likly environmental changes, as this will ultimatly determine the choice of a suitable location.
Here is a list of stuff that could possibly occur.
- Volcanoes (perhaps the caldera at Yellowstone, causing the blocking out of the sun, causing an ice age type event)
- Earthquakes (causing tsunamis)
- Solar Flares (causing electronic malfunctions of various telecommun ications equipment)
- Magnetic pole variations (possible electrical equipment malfunction)
- Thunderstorm activity (tornadoes, hurricanes, blizzards, etc etc)
If you can think of other events please add them.
Now some pre-requisites to having a place to support a long term self sufficient society.
- Resources (timber, livestock, farmable soil, stone, fresh water, fishing)
- Quick access to both high altitude, and low-altitude areas
- Abililty to create underground systems (for added underground protection if needed)
- Running streams or water systems for hydro-electric (preferably underground streams for added protection of the systems)
Please add anything that you would also see fit. I am pretty sure that most of these list items are pretty self-explanatory.
With these things in mind, here is what I would look for.
A cavern or cave complex of some sort, which extends both deep below the surface, and extends high into a mountain or mesa of some sort.
I would not just blindly decide to go very high into the mountain to run from a flood. There could quite possibly be an ice age type event and you could end up freezing to death. And on the opposite side you may encounter floods which would make you need to go to these higher elevations. This is why I would try to find a location where either area is easily accesible.
Those are my thoughts.



