I came across this article today. "Can You Imagine America Without Los Angeles", and the first thing I imagined was a huge influx of refugees into Las Vegas. Currently, every weekend sees a huge influx of people driving and flying into Vegas from LA and holidays are a special type of Hell for those coming to the city pre-holiday and leaving the city post-holiday from southern California. Add any sort of major accident (or wildfire or snow as has happened in the past) and the freeways can be closed for many hours.
No matter where you live, it is a good exercise to consider what would happen if a major disaster strikes not the area you live in, but a nearby major city. Where do you think all of those people would go if their city becomes unlivable? Even folks who live in the mountains aren't safe as that seems to be city folk's main form of disaster preparedness--heading for the hills. If you live in the hills that is not a good thing.
How would you protect yourself, your family, and your preps in this scenario? How would you help such refugees or would you even do so? What would happen to your area with a huge influx of people? Stores would probably be out of everything within hours, similar to what happens when a big storm is forecast, and general infrastructure would definitely be impacted. This is yet another area to consider when you are doing your disaster preparedness planning.