May I add a little from one of my own specialities here, an interesting point that arises from long distance movement and complete relocation of a group of persons is the lack of geographical dispersal at the point of arrival (certainly within initial immigrant groups) -as AD mentions very appositely Italians migrating to the USA had very specific initial "landfall" areas .You see this pattern oft repeated when rural populations move into large urban areas-people from Monaghan moving into Dublin for example forming specific enclaves The linguistic reprucussions are very interesting, perhaps preserving archaic/pure forms in remote enclaves .
The Ubian removal to Upper Germania (if I remember correctly) is an appropriate example from our own target period.I am just reading the excellent "Hermes the Thief" (as suggested by Pantagathus -and due for review on this site by him) which rather knocks some of the much vaunted "central place theory" of Christaller and Loesch into the bin , demonstrating as it does the agora as the boundary (in ancient Greece ) rather than the central market area:this made me think very hard about the role of the autonomous village/community and its fear of "the stranger" or the other in ancient society -if a community had no choice but to relocate (famine/war/disaster) then I suggest wholesale movement as a coherent group as a norm rather than fracturing of a community. Im sure there will be suggestions that division might occur across class lines in later societies .
just some musings