I have notice in a number of books involving a societal break down within the United States, that at some point large masses of people move out of the cities into the countryside in a mass exodus. In the case of “One Second After” a large number of people walk all the way from Charlotte North Carolina up into the mountainous Asheville North Carolina with no apparent connection to the area or solid plan in mind.
This strikes me as an odd understanding of how people choose to move in migratory, and refugee situations.
In migratory patterns people move to known areas of opportunity. In traditional settings, a small group of path breakers goes first, and on scoping out the lay of the land, help follow up groups come in behind them. In North Carolina a typical pattern might be that the Grandparents retire to the relatively inexpensive (from where they live) Wake County, North Carolina. Their adult children visit them and when one of them losses their job back in the home state, they decide to move. As time goes on, more and more people make the move until the “families” critical mass is now in the new location, and if people want to maintain close contact with their family they are obligated to move as well. This pattern could just as well start with one of the adult children finding a job, and parents move to be close to grand children. It also can work with social groupings. Oddly enough these migratory patterns play out throughout history, and the Germanic Invasions actually play out at times as more of an extended migratory event than as an actual invasion. link
In the case of refugees, they are generally single mass movements that force a block of people to move as one: the impetus is generally fear and poverty. However, in most of the scenarios postulated, there is no great impetus of fear. Conditions are bad, but there is no difference between the area that people are in and some other place. If there was an increase in violent racism as an example, than certain groups might indeed pick up and move. But they are likely to be individual groups with a common purpose, not the ad hoc hordes generally described. link (hit the pdf button in middle of box)
A more realistic assessment of a collapse scenario would be that isolated individuals will seek out family members.
Once a group moves, it generally becomes more prone to making secondary moves. So at the point that there is some coalescing of the group, there may a secondary move (probably to another family or associated) group if there is thought to be a better situation.
Where there is violence directed at groups, the less well off groups are likely to move out. Since they do not have much economic wear withal to begin with, they have less incentive to stay. As the economic situation degrades (at a variable rate) the impetus to move in mass will increase.
So in summary, the large threat to the individual are far more likely to be confiscatory policies by the “authorities” under emergency powers, and scavenging theft by the locals, rather than the Golden Horde coming out of your mega metropolis.