What's funny about the primitive plans for dealing with a catastrophe such as this--and the normally sensible "preppers" too--is that they assume in case of such an event, law and order will persevere; that everybody will be allowed to keep what they have.
Hah.
I suggest the primitives and preppers both consult history, to see what happens in cases of widespread panic, disorder, and anarchy. About the only people who'll be safe are people with firearms and other weapons, and people who know how to use them.
<<<has no plans for surviving a catastrophe; when it happens, will adapt as needed.